Use of GDF-15 in the Diagnosis and Treatment of Frailty and Conditions Associated with Altered Physiological Reserve, Physical Fitness and Exercise Capacity

Abstract

Provided herein are biomarkers useful for determining frailty, a biomarker signature for frailty, and methods of using the biomarkers to identify, classify, and treat a subject having frailty. Provided herein are also biomarkers useful for determining, identifying, classifying, and treating conditions associated with altered physical reserve, physical fitness, and exercise capacity.

Description

FIELD

This application relates to the identification, stratification, and treatment of frailty and conditions associated with altered physiological reserve, physical fitness and exercise capacity.

BACKGROUND

Frailty is a complex multidomain syndrome characterized by a decline in systemic physiological reserve, reduced physical health and fitness, and an accumulation of multiple medical comorbidities (‘multimorbidity’), including hypertension and diabetes mellitus. Frailty encompasses a conglomerate of signs, symptoms and clinical findings, including skeletal muscle wasting (sarcopenia), reduced muscle strength, progressive unintentional weight loss (cachexia), anorexia, systemic inflammation (‘inflammaging’), neurohormonal maladaptation, immune dysfunction, and depression. Frailty is a serious problem because it is difficult to detect, yet once it appears, can quickly lead to increased morbidity in a patient. However, studies have shown that frailty is potentially reversible and may even transition between non-frail/pre-frail and frail states through time. For all of the above reasons, there is a strong need for new methods of identifying and treating frailty in patients.

SUMMARY OF THE INVENTION

Provided herein is one or more blood biomarkers that can detect, diagnose, gauge, profile, classify or stratify frailty. In some embodiments, provided is a method of using one or more circulating blood biomarkers optionally in combination with metabolites or metabolomics to detect, diagnose, gauge, profile, classify or stratify frailty. Some embodiments provide a method of monitoring frailty status over time. Another embodiment provides a methodological process using one or more blood biomarkers for profiling, classifying, diagnosing and risk stratifying conditions associated with altered physical reserve, physical fitness or exercise capacity. In some embodiments, the blood biomarker is growth differentiation factor 15 (GDF-15), also known as macrophage inhibitory cytokine 1 (MIC-1).

Another embodiment provides a methodological process for profiling, classifying, diagnosing and risk stratifying the clinical syndrome of frailty with/without cardiac dysfunction (CD) through the use of one or more biomarkers, including but not limited to GDF-15 and NT-proBNP (N-terminal prohormone of B-type (brain) natriuretic peptide), coupled with metabolic/metabolomic profiling.

Another embodiment provides a method of determining frailty severity in a subject comprising the steps of

• • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, and GlycA.

Some embodiments further comprise the step of measuring the levels of one or more biomarkers selected from the group consisting of phosphoglycerides, glycine, and alanine.

Some embodiments further comprise the step of determining frailty severity according to methods described herein, and treating the subject determined to have severe frailty.

Yet another embodiment provides a method of using of a biomarker in combination with metabolic or metabolomic profiling to provide a comprehensive high-dimensional picture of a subject's total health condition (e.g. internal milieu). In some embodiments, the total health conditions include one or more pathophysiological diagnoses and/or monitoring of such conditions.

Another embodiment provides the use of GDF-15 and NT-proBNP, optionally with the metabolome, to identify, define, characterize, diagnose and profile the frailty and non-frailty spectrum from robust to frail status, particularly in the subphenotyping or classification of individuals with and without CD.

Up until now there has been no available blood biomarker or imaging test that can reliably detect, diagnose, classify or risk stratify frailty. Accordingly, the biomarkers and methods provided herein solve such a problem and furthermore have several advantages over current solutions.

In some embodiments the use of circulating biomarker(s) and a broad array of metabolic measures/features (metabolomics) provides quantitation of differences between disease states and/or disorders, and serves as objective measures over time.

In some embodiments the provided methods provide objective testing, diagnosis and monitoring of frailty which are improvements over frailty assessment schemes based on point scoring along multidomain scales (e.g. Fried phenotype assessment [Fried 2001]) which are limited by subjectivity, recall bias, interobserver variability, require the subject to have a certain level of auditory, cognitive and mental competence, and pertain to domains that are under the influence of metabolic, neurohormonal and circulating factors in the bloodstream.

In some embodiments, the use of the ¹H-nuclear magnetic resonance (NMR) Nightingale or similar platform coupled with functional biomarkers (e.g. NT-proBNP, GDF-15) provides more accurate and advanced frailty-related diagnostics, classification of health status, and health and disease management.

In some embodiments, the combination of biomarkers with metabolomics (biomarker-guided metabolomics) provides a comprehensive high-dimensional picture of the internal milieu.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will be readily understood by the following detailed description in conjunction with the accompanying figures.

FIG. 1 shows receiver operative characteristic (ROC) curves for CD for different biomarkers.

FIG. 2A shows metabolomic biosignatures of NT-proBNP according to CD status for 250 metabolites/metabolic features and the strength of the association between NT-proBNP and the metabolites measured using the β coefficient values.

FIG. 2B shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2C shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2D shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2E shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2F shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2G shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2H shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2I shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 2J shows continued metabolomic biosignatures of NT-proBNP of FIG. 2A thereof.

FIG. 3A shows metabolic profiles of paired comparisons among frailty status.

FIG. 3B shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3C shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3D shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3E shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3F shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3G shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3H shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3I shows continued metabolic profiles of FIG. 3A thereof.

FIG. 3J shows continued metabolic profiles of FIG. 3A thereof.

FIG. 4A(i) shows a discovery set of metabolic profiles of GDF-15 shifted with frailty status.

FIG. 4A(ii) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(iii) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(iv) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(v) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(vi) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(vii) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(viii) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(ix) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4A(x) shows a continued discovery set of metabolic profiles of GDF-15 of FIG. 4A(i) thereof.

FIG. 4B(i) shows a replication/validation set of metabolic profiles of GDF-15 shifted with frailty status.

FIG. 4B(ii) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(iii) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(iv) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(v) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(vi) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(vii) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(viii) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(ix) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4B(x) shows a continued replication/validation set of metabolic profiles of GDF-15 of FIG. 4B(i) thereof.

FIG. 4C(i) shows a combined set of discovery and replication/validation of metabolic profiles of GDF-15 shifted with frailty status.

FIG. 4C(ii) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(iii) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(iv) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(v) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(vi) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(vii) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(viii) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(ix) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 4C(x) shows a continued combined set of discovery and replication/validation of metabolic profiles of GDF-15 of FIG. 4C(i) thereof.

FIG. 5A shows receiver operating characteristic (ROC) curve for a discovery set of the combined classifiers GDF-15, albumin, glutamine, glycoprotein actetylation marker of inflammation (GlycA), and phosphoglycerides), age and sex in predicting frailty (area under the curve AUC).

FIG. 5B shows receiver operating characteristic (ROC) curve for a set of discovery and replication/validation of the combined classifiers GDF-15, albumin, glutamine, glycoprotein actetylation marker of inflammation (GlycA), and phosphoglycerides), age and sex in predicting frailty (area under the curve AUC).

FIG. 6 shows a workflow of logistic regression analysis with adjustment for age and sex.

FIG. 7 shows a workflow of age- and sex-adjusted linear regression.

DETAILED DESCRIPTION

Throughout this description for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the many aspects and embodiments disclosed herein. It will be apparent, however, to one skilled in the art that the many aspects and embodiments may be practiced without some of these specific details. In other instances, known biological and biochemical entities, mechanisms and analyses are shown herein to avoid obscuring the underlying principles of the described aspects and embodiments. The present invention is in the technical field of diagnostics, classification of health status, and human health and disease management.

Definitions and Abbreviations

As used herein and in the claims, the terms “comprise” (or any related form such as “comprises” and “comprising”), “include” (or any related forms such as “includes” or “including”), “contain” (or any related forms such as “contains” or “containing”), means including the following elements but not excluding others. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Where a range is referred in the specification, the range is understood to include each discrete point within the range. For example, 1-7 means 1, 2, 3, 4, 5, 6, and 7.

As used herein and in the claims, an “effective amount”, is an amount that is effective to achieve at least a measurable amount of a desired effect. For example, the amount may be effective to elicit an immune response, and/or it may be effective to elicit a protective response, against a pathogen bearing the polypeptide of interest. In some embodiments, the amount may be effective to maintain stable health, increase mobility, improved ability to retain nutrients, or improve FRAIL test results.

As used herein and in the claims, a “subject” refers to animals such as mammals and vertebrates, including, but not limited to, primates (e.g. humans), cows, sheep, goats, horses, pigs, dogs, cats, rabbits, rats, mice, frogs, zebrafish and the like.

As used herein, the term “treat,” “treating” or “treatment” refers to methods of alleviating, abating or ameliorating a disease or condition symptoms, preventing additional symptoms, ameliorating or preventing the underlying metabolic causes of symptoms, inhibiting the disease or condition, arresting the development of the disease or condition, relieving the disease or condition, causing regression of the disease or condition, relieving a condition caused by the disease or condition, or stopping the symptoms of the disease or condition either prophylactically and/or therapeutically.

“GDF-15” means growth differentiation factor 15.

“NT-proBNP” means N-terminal prohormone of B-type (brain) natriuretic peptide, a biomarker of cardiac dysfunction.

“CD” means cardiac dysfunction.

“CI” means confidence interval.

“NS” means not significant.

“OR” means odds ratio.

“GlycA” means glycoprotein acetylation marker of inflammation measured clinically in blood by the presence of certain characteristic N-acetyl methyl group protons which are detectable by ¹H-NMR.

“Albumin” is a globular protein detectable in blood.

“Phosphoglycerides” is glycerol-based phospholipids.

Amino acids herein may be referred to by their full names or their abbreviated names, including, but not limited to, the below list:

Alanine: Ala
Arginine: Arg
Asparagine: Asn
Aspartic acid: Asp
Cysteine: Cys
Glutamic acid: Glu
Glutamine: Gln
Glycine: Gly
Histidine: His
Isoleucine: Ile
Leucine: Leu
Lysine: Lys
Methionine: Met
Phenylalanine: Phe
Proline: Pro
Serine: Ser
Threonine: Thr
Tryptophan: Trp
Tyrosine: Tyr
Valine: Val

Although the description referred to particular aspects and embodiments, the disclosure should not be construed as limited to the embodiments set forth herein.

One aspect provides an in vitro method of determining frailty severity in a subject comprising the steps of

• • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) determining the subject as being frail if the level of the biomarker in the biological sample is higher than about 2,000 pg/ml to 6,000 pg/ml; pre-frail if the level of the biomarker in the biological sample is higher than 500 pg/ml to 2000 pg/ml; and robust if the level of the biomarker in the biological sample is less than 500 pg/ml.

Another aspect provides an in vitro method of determining frailty severity in a subject comprising the steps of

• • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;
  • c) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • d) determining the subject as being frail if the score p is a value defined in Table 1 wherein the corresponding sensitivity and specificity values add up to between 1.4 and 1.5.

Another aspect provides a method of determining frailty severity in a subject comprising the steps of

• • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;
  • c) determining the overall biosignature score p; and
  • d) determining the subject as being frail if p is Z;
    • wherein Z is a value defined in Table 1 wherein the corresponding sensitivity and specificity values add up to between 1.4 and 1.5;
  • wherein the score p is determined by
    • i) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • or
    • ii) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and log₁₀-transformed serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=-25.54+\left(-0.95\times \mathrm{sex}\right)+\left(0.10\times \mathrm{age}\right)+\left(1.20\times \mathrm{GDF}-15\right)+\left(7.26\times \mathrm{Gln}\right)+\left(10.0\times \mathrm{albumin}\right)+\left(6.30\times \mathrm{GlycA}\right)+\left(-3.11\times \mathrm{phosphoglycerides}\right)+\left(3.22\times \mathrm{Gly}\right)+\left(-0.97\times \mathrm{Ala}\right).$

Another aspect provides a method of determining frailty severity in a subject comprising the steps of

• a) measuring the levels of GDF-15 in a biological sample from the subject;
• b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;
• c) determining the overall biosignature score p; and
• d) determining the subject as being frail if p is Z;
  • wherein Z is a value defined in Table 1 wherein the corresponding sensitivity and specificity values add up to between 1.4 and 1.5;
    • wherein the score p is determined by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and log₁₀-transformed serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=-25.54+\left(-0.95\times \mathrm{sex}\right)+\left(0.10\times \mathrm{age}\right)+\left(1.20\times \mathrm{GDF}-15\right)+\left(7.26\times \mathrm{Gln}\right)+\left(10.0\times \mathrm{albumin}\right)+\left(6.30\times \mathrm{GlycA}\right)+\left(-3.11\times \mathrm{phosphoglycerides}\right)+\left(3.22\times \mathrm{Gly}\right)+\left(-0.97\times \mathrm{Ala}\right).$

Another aspect provides a method of determining frailty severity in a subject comprising the steps of

• a) measuring the levels of GDF-15 in a biological sample from the subject;
• b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;
• c) determining the overall biosignature score p; and
• d) determining the subject as being frail if p is Z;
  • wherein Z is a value defined in Table 1 wherein the corresponding sensitivity and specificity values add up to between 1.4 and 1.5;
    • wherein the score p is determined by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and log₁₀-transformed serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=-25.54+\left(-0.95\times \mathrm{sex}\right)+\left(0.10\times \mathrm{age}\right)+\left(1.20\times \mathrm{GDF}-15\right)+\left(7.26\times \mathrm{Gln}\right)+\left(10.0\times \mathrm{albumin}\right)+\left(6.30\times \mathrm{GlycA}\right)+\left(-3.11\times \mathrm{phosphoglycerides}\right)+\left(3.22\times \mathrm{Gly}\right)+\left(-0.97\times \mathrm{Ala}\right).$

In some embodiments, the method is an in vitro method.

In some embodiments, the Z is 0.15 to 0.56. In some embodiments, Z is 0.259 or Youden's J statistic. In some embodiments, the value defined by Table 1 wherein the corresponding sensitivity and specificity values add up to between 1.4 and 1.5 is 0.15 to 0.56; in other embodiments, 0.259 or Youden's J statistic. In some embodiments, the score p is 0.15 to 0.56. In some embodiments, the score p is 0.259 or Youden's J statistic.

Some embodiments further comprise the step of wherein if the subject is determined to be frail, treating the subject with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function. In some embodiments, the therapeutic drug is a combined angiotensin receptor blocker and neprilysin inhibitor (e.g. sacubitril/valsartan), a sodium-glucose transport protein 2 (SGLT2) inhibitor or gliflozins (e.g. dapagliflozin, empagliflozin), a beta blocker (e.g. metoprolol, carvedilol, bisoprolol), renin-angiotensin system inhibitor (e.g. enalapril, lisinopril), mineralocorticoid receptor antagonist (e.g. eplerenone, spironolactone), ivabradine, digoxin, inotropes (e.g. dobutamine, milrinone) or inodilator (e.g. levosimendan).

Some embodiments further comprise the step of measuring the levels of NT-proBNP, wherein if NT-proBNP levels are elevated but GDF-15 levels are not, determining the subject has cardiac dysfunction without frailty; if GDF-15 levels are elevated but NT-proBNP are not, determining the subject has systemic physiological injury or inflammation, hypoperfusion, or non-cardiac frailty; and if both GDF-15 and NT-proBNP levels are elevated, determining the subject has frailty and is predicted to have heart failure. In some embodiments, the subject has cardiac dysfunction, systemic tissue injury or hypoperfusion which can lead to heart failure.

Table 1 below shows thresholds and associated sensitivity, specificity values and Youden's index values (J) for the biosignature score p.

TABLE 1
	Thresholds	sensitivity	specificity	J
1	-Inf	1	0	0
2	0.0149	1	0.00493	0.00493
3	0.0172	1	0.00985	0.00985
4	0.0194	1	0.0148	0.0148
5	0.0199	1	0.0197	0.0197
6	0.0218	1	0.0246	0.0246
7	0.0242	1	0.0296	0.0296
8	0.0247	1	0.0345	0.0345
9	0.026	1	0.0394	0.0394
10	0.0285	1	0.0443	0.0443
11	0.0304	1	0.0493	0.0493
12	0.031	1	0.0542	0.0542
13	0.0315	1	0.0591	0.0591
14	0.033	1	0.064	0.064
15	0.0339	1	0.069	0.069
16	0.0344	1	0.0739	0.0739
17	0.0353	0.989	0.0739	0.0629
18	0.0369	0.989	0.0788	0.0678
19	0.0383	0.989	0.0837	0.0727
20	0.0384	0.989	0.0887	0.0777
21	0.0387	0.989	0.0936	0.0826
22	0.0401	0.989	0.0985	0.0875
23	0.0414	0.989	0.103	0.092
24	0.0415	0.989	0.108	0.097
25	0.0417	0.989	0.113	0.102
26	0.0419	0.989	0.118	0.107
27	0.0422	0.989	0.123	0.112
28	0.0427	0.989	0.128	0.117
29	0.043	0.989	0.133	0.122
30	0.0434	0.989	0.138	0.127
31	0.0439	0.989	0.143	0.132
32	0.0444	0.989	0.148	0.137
33	0.0448	0.989	0.153	0.142
34	0.0455	0.989	0.158	0.147
35	0.0488	0.989	0.163	0.152
36	0.0533	0.989	0.167	0.156
37	0.0553	0.989	0.172	0.161
38	0.0556	0.989	0.177	0.166
39	0.0568	0.978	0.177	0.155
40	0.0581	0.978	0.182	0.16
41	0.0591	0.978	0.187	0.165
42	0.0602	0.978	0.192	0.17
43	0.0609	0.978	0.197	0.175
44	0.0621	0.968	0.197	0.165
45	0.0631	0.968	0.202	0.17
46	0.0635	0.968	0.207	0.175
47	0.0638	0.968	0.212	0.18
48	0.0642	0.968	0.217	0.185
49	0.0643	0.968	0.222	0.19
50	0.0653	0.968	0.227	0.195
51	0.0673	0.968	0.232	0.2
52	0.0697	0.968	0.236	0.204
53	0.0719	0.968	0.241	0.209
54	0.0728	0.968	0.246	0.214
55	0.0731	0.968	0.251	0.219
56	0.0736	0.968	0.256	0.224
57	0.0742	0.968	0.261	0.229
58	0.0744	0.968	0.266	0.234
59	0.0752	0.968	0.271	0.239
60	0.0767	0.968	0.276	0.244
61	0.0781	0.968	0.281	0.249
62	0.0789	0.968	0.286	0.254
63	0.0795	0.968	0.291	0.259
64	0.0807	0.968	0.296	0.264
65	0.0823	0.968	0.3	0.268
66	0.0842	0.968	0.305	0.273
67	0.0854	0.968	0.31	0.278
68	0.0869	0.968	0.315	0.283
69	0.0882	0.968	0.32	0.288
70	0.0884	0.968	0.325	0.293
71	0.0889	0.968	0.33	0.298
72	0.0893	0.968	0.335	0.303
73	0.0901	0.968	0.34	0.308
74	0.091	0.968	0.345	0.313
75	0.0918	0.968	0.35	0.318
76	0.0953	0.968	0.355	0.323
77	0.0984	0.968	0.36	0.328
78	0.0992	0.968	0.365	0.333
79	0.0996	0.968	0.369	0.337
80	0.0998	0.968	0.374	0.342
81	0.1	0.968	0.379	0.347
82	0.102	0.968	0.384	0.352
83	0.104	0.968	0.389	0.357
84	0.106	0.968	0.394	0.362
85	0.107	0.968	0.399	0.367
86	0.108	0.968	0.404	0.372
87	0.109	0.968	0.409	0.377
88	0.11	0.968	0.414	0.382
89	0.111	0.968	0.419	0.387
90	0.112	0.968	0.424	0.392
91	0.112	0.968	0.429	0.397
92	0.115	0.968	0.433	0.401
93	0.119	0.957	0.433	0.39
94	0.125	0.957	0.438	0.395
95	0.131	0.957	0.443	0.4
96	0.131	0.957	0.448	0.405
97	0.132	0.957	0.453	0.41
98	0.132	0.957	0.458	0.415
99	0.133	0.957	0.463	0.42
100	0.135	0.957	0.468	0.425
101	0.136	0.957	0.473	0.43
102	0.138	0.957	0.478	0.435
103	0.141	0.957	0.483	0.44
104	0.143	0.957	0.488	0.445
105	0.144	0.957	0.493	0.45
106	0.144	0.957	0.498	0.455
107	0.146	0.957	0.502	0.459
108	0.146	0.957	0.507	0.464
109	0.148	0.946	0.507	0.453
110	0.151	0.946	0.512	0.458
111	0.152	0.946	0.517	0.463
112	0.153	0.946	0.522	0.468
113	0.154	0.946	0.527	0.473
114	0.155	0.946	0.532	0.478
115	0.155	0.946	0.537	0.483
116	0.157	0.946	0.542	0.488
117	0.161	0.946	0.547	0.493
118	0.164	0.946	0.552	0.498
119	0.165	0.946	0.557	0.503
120	0.167	0.935	0.557	0.492
121	0.168	0.935	0.562	0.497
122	0.17	0.925	0.562	0.487
123	0.172	0.925	0.567	0.492
124	0.172	0.925	0.571	0.496
125	0.174	0.925	0.576	0.501
126	0.175	0.925	0.581	0.506
127	0.176	0.914	0.581	0.495
128	0.178	0.914	0.586	0.5
129	0.18	0.914	0.591	0.505
130	0.183	0.914	0.596	0.51
131	0.185	0.914	0.601	0.515
132	0.186	0.903	0.601	0.504
133	0.188	0.903	0.606	0.509
134	0.192	0.903	0.611	0.514
135	0.197	0.903	0.616	0.519
136	0.202	0.903	0.621	0.524
137	0.206	0.892	0.621	0.513
138	0.21	0.892	0.626	0.518
139	0.212	0.892	0.631	0.523
140	0.212	0.892	0.635	0.527
141	0.214	0.882	0.635	0.517
142	0.215	0.871	0.635	0.506
143	0.217	0.871	0.64	0.511
144	0.22	0.871	0.645	0.516
145	0.222	0.871	0.65	0.521
146	0.223	0.871	0.655	0.526
147	0.223	0.871	0.66	0.531
148	0.227	0.871	0.665	0.536
149	0.232	0.871	0.67	0.541
150	0.234	0.871	0.675	0.546
151	0.235	0.86	0.675	0.535
152	0.237	0.86	0.68	0.54
153	0.238	0.86	0.685	0.545
154	0.24	0.849	0.685	0.534
155	0.241	0.849	0.69	0.539
156	0.242	0.849	0.695	0.544
157	0.247	0.839	0.695	0.534
158	0.254	0.839	0.7	0.539
159	0.258	0.839	0.704	0.543
160	0.259	0.839	0.709	0.548
161	0.259	0.839	0.714	0.553
162	0.26	0.828	0.714	0.542
163	0.262	0.817	0.714	0.531
164	0.264	0.817	0.719	0.536
165	0.267	0.817	0.724	0.541
166	0.269	0.817	0.729	0.546
167	0.274	0.806	0.729	0.535
168	0.28	0.796	0.729	0.525
169	0.283	0.785	0.729	0.514
170	0.286	0.785	0.734	0.519
171	0.288	0.774	0.734	0.508
172	0.289	0.774	0.739	0.513
173	0.292	0.774	0.744	0.518
174	0.296	0.774	0.749	0.523
175	0.305	0.774	0.754	0.528
176	0.315	0.763	0.754	0.517
177	0.318	0.763	0.759	0.522
178	0.318	0.763	0.764	0.527
179	0.319	0.763	0.768	0.531
180	0.32	0.753	0.768	0.521
181	0.321	0.742	0.768	0.51
182	0.321	0.742	0.773	0.515
183	0.322	0.731	0.773	0.504
184	0.323	0.72	0.773	0.493
185	0.324	0.72	0.778	0.498
186	0.325	0.72	0.783	0.503
187	0.325	0.72	0.788	0.508
188	0.326	0.72	0.793	0.513
189	0.328	0.71	0.793	0.503
190	0.33	0.71	0.798	0.508
191	0.333	0.71	0.803	0.513
192	0.337	0.71	0.808	0.518
193	0.341	0.699	0.808	0.507
194	0.347	0.699	0.813	0.512
195	0.349	0.699	0.818	0.517
196	0.356	0.699	0.823	0.522
197	0.366	0.688	0.823	0.511
198	0.38	0.688	0.828	0.516
199	0.39	0.688	0.833	0.521
200	0.396	0.688	0.837	0.525
201	0.402	0.688	0.842	0.53
202	0.406	0.688	0.847	0.535
203	0.408	0.677	0.847	0.524
204	0.413	0.667	0.847	0.514
205	0.422	0.667	0.852	0.519
206	0.428	0.667	0.857	0.524
207	0.432	0.667	0.862	0.529
208	0.435	0.667	0.867	0.534
209	0.44	0.656	0.867	0.523
210	0.443	0.656	0.872	0.528
211	0.444	0.645	0.872	0.517
212	0.449	0.645	0.877	0.522
213	0.455	0.645	0.882	0.527
214	0.46	0.634	0.882	0.516
215	0.465	0.624	0.882	0.506
216	0.466	0.613	0.882	0.495
217	0.47	0.602	0.882	0.484
218	0.474	0.602	0.887	0.489
219	0.476	0.591	0.887	0.478
220	0.476	0.581	0.887	0.468
221	0.477	0.57	0.887	0.457
222	0.481	0.57	0.892	0.462
223	0.491	0.559	0.892	0.451
224	0.498	0.559	0.897	0.456
225	0.501	0.559	0.901	0.46
226	0.51	0.548	0.901	0.449
227	0.519	0.548	0.906	0.454
228	0.522	0.538	0.906	0.444
229	0.527	0.527	0.906	0.433
230	0.534	0.527	0.911	0.438
231	0.539	0.516	0.911	0.427
232	0.541	0.516	0.916	0.432
233	0.548	0.516	0.921	0.437
234	0.558	0.516	0.926	0.442
235	0.563	0.505	0.926	0.431
236	0.568	0.495	0.926	0.421
237	0.574	0.495	0.931	0.426
238	0.578	0.484	0.931	0.415
239	0.584	0.473	0.931	0.404
240	0.588	0.462	0.931	0.393
241	0.59	0.452	0.931	0.383
242	0.594	0.441	0.931	0.372
243	0.597	0.43	0.931	0.361
244	0.6	0.43	0.936	0.366
245	0.607	0.419	0.936	0.355
246	0.612	0.409	0.936	0.345
247	0.615	0.398	0.936	0.334
248	0.621	0.387	0.936	0.323
249	0.635	0.376	0.936	0.312
250	0.646	0.376	0.941	0.317
251	0.646	0.366	0.941	0.307
252	0.648	0.366	0.946	0.312
253	0.65	0.355	0.946	0.301
254	0.651	0.344	0.946	0.29
255	0.655	0.344	0.951	0.295
256	0.657	0.344	0.956	0.3
257	0.659	0.333	0.956	0.289
258	0.661	0.333	0.961	0.294
259	0.663	0.323	0.961	0.284
260	0.666	0.312	0.961	0.273
261	0.679	0.301	0.961	0.262
262	0.691	0.29	0.961	0.251
263	0.692	0.28	0.961	0.241
264	0.695	0.269	0.961	0.23
265	0.702	0.258	0.961	0.219
266	0.709	0.247	0.961	0.208
267	0.717	0.237	0.961	0.198
268	0.727	0.226	0.961	0.187
269	0.731	0.226	0.966	0.192
270	0.733	0.215	0.966	0.181
271	0.735	0.204	0.966	0.17
272	0.742	0.194	0.966	0.16
273	0.759	0.183	0.966	0.149
274	0.769	0.172	0.966	0.138
275	0.771	0.161	0.966	0.127
276	0.78	0.161	0.97	0.131
277	0.796	0.151	0.97	0.121
278	0.809	0.14	0.97	0.11
279	0.816	0.129	0.97	0.099
280	0.823	0.129	0.975	0.104
281	0.837	0.129	0.98	0.109
282	0.856	0.118	0.98	0.098
283	0.864	0.108	0.98	0.088
284	0.865	0.0968	0.98	0.0768
285	0.867	0.086	0.98	0.066
286	0.874	0.086	0.985	0.071
287	0.879	0.0753	0.985	0.0603
288	0.884	0.0645	0.985	0.0495
289	0.89	0.0538	0.985	0.0388
290	0.894	0.0538	0.99	0.0438
291	0.908	0.0538	0.995	0.0488
292	0.93	0.043	0.995	0.038
293	0.95	0.043	1	0.043
294	0.963	0.0323	1	0.0323
295	0.973	0.0215	1	0.0215
296	0.987	0.0108	1	0.0108
297	Inf	0	1	0

Some embodiments further comprise the step of treating the subject for heart failure if NT-proBNP levels are elevated but GDF-15 levels are not; treating the subject for systemic physiological injury or inflammation, hypoperfusion, or non-cardiac frailty with a drug if GDF-15 levels are elevated but NT-proBNP are not; treating the subject with a heart failure and frailty drug if both GDF-15 and NT-proBNP levels are elevated.

Some embodiments further comprise the step of treating the subject in accordance with guideline-directed medical therapy (GDMT); wherein if the subject has elevated levels of both NT-proBNP and GDF-15, treating the subject as advanced stage D in accordance with GDMT; if the subject has elevated levels of NT-proBNP but not elevated levels of GDF-15, conducting cardiac imaging to determine the causes of cardiac dysfunction and treating the cardiac dysfunction in accordance with stage B or C in accordance with GDMT; if the subject has elevated levels of GDF-15 but not elevated levels of NT-proBNP, conducting a clinical assessment of medical comorbidities and treating the subject in accordance with stage B or C in accordance with GDMT; and if the subject does not have elevated levels of either NT-proBNP or GDF-15, treating the patient with as stage A in accordance with GDMT, particularly when the subject experiences no symptoms and/or when there are no cardiac structural abnormalities identified by imaging. In some embodiments, if the subject does not have elevated levels of either NT-proBNP or GDF-15 with/without the performance of other tests to exclude functional and/or structural abnormalities in the heart as deemed appropriate by the treating physician and according to standard practice guidelines, advising the subject on lifestyle modifications and managing particular risk factors without medical or therapeutic intervention.

In some embodiments, the stages A through D of the GDMT are based on the American College of Cardiology/American Heart Association (ACC/AHA) staging framework. In some embodiments, the treatments may be selected from one or more of pharmacological, device and other interventional therapies.

Another aspect provides a method of identifying and treating frailty, altered physiological and physical reserve, aging, or aging-related inflammation in a subject comprising the steps of

• • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;
  • c) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • d) determining the subject as being frail if the score p is a value defined by a threshold value in Table 1 wherein the corresponding sensitivity and specificity values of the threshold value add up to between 1.4 and 1.6; and wherein at least one of the sensitivity or specificity values is 0.5 or above.

In some embodiments, the score p is 0.15 to 0.56. In some embodiments, the score p is 0.259. In some embodiments, the score p is a threshold value having a maximum value of Youden's J statistic. In a further embodiment, the maximum value of Youden's J statistic is 0.553.

Another aspect provides a method of generating a biosignature for frailty comprising the steps of

Identifying a subpopulation with elevated levels of GDF-15;

Conducting a biomarker screen/metabolic/metabolomic profiling on the subpopulation and using mathematical modeling tools to identifying biomarkers that correlate with the subpopulation.

In some embodiments, the biomarker screen includes a disease-specific biomarker selected from one or more of a heart failure biomarker (NT-proBNP or BNP), a renal failure biomarker (serum creatinine alone or in combination with cystatin C (CysC), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1) and/or neutrophil-gelatinase-associated lipocalin (NGAL)), a panel of inflammatory biomarkers (proinflammatory cytokines, e.g. interleukins, chemokines), and a tissue-specific biomarker.

Another aspect provides a system for detecting frailty in a subject comprising:

• • a) a GDF-15 analyzer configured to analyze biological samples from the subject to provide a concentration of GDF-15 in the biological sample;
  • b) a computer programmed to execute the following steps:
    • i) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/l), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{Phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • • ii) determining the subject as being frail if the score p is 0.15 to 0.56.

Another aspect provides a system for detecting frailty in a subject comprising:

• • a) a GDF-15 analyzer configured to analyze biological samples from the subject to provide a concentration of GDF-15 in the biological sample;
  • b) a computer programmed to execute at least the following:
    • i) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • or
    • ii) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and log₁₀-transformed serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=-25.54+\left(-0.95\times \mathrm{sex}\right)+\left(0.10\times \mathrm{age}\right)+\left(1.20\times \mathrm{GDF}-15\right)+\left(7.26\times \mathrm{Gln}\right)+\left(10.0\times \mathrm{albumin}\right)+\left(6.30\times \mathrm{GlycA}\right)+\left(-3.11\times \mathrm{phosphoglycerides}\right)+\left(3.22\times \mathrm{Gly}\right)+\left(-0.97\times \mathrm{Ala}\right);$

and

• • • iii) determining the subject as being frail if the score p is 0.15 to 0.56.

Another aspect provides a method of improving the accuracy of frailty and non-frailty classification comprising using GDF-15 as a guiding biomarker with a metabolomic panel of metabolites selected from one or more of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine; comprising the following steps:

• • a) measuring GDF-15 concentration in a blood serum or plasma sample from a subject using the Roche Elecsys Assay kit on a Roche Cobas e immunoassay analyzer;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine using ¹H-NMR Nightingale metabolomic profiling;
  • c) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

and

• • d) determining the subject as being frail if the score p is 0.15 to 0.56.

Another aspect provides a method of identifying subjects who will have improved survival outcomes when treated with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function; comprising the steps of

• • a) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • b) determining the subject as being frail if the score p is 0.15 to 0.56; and
  • c) treating the subjects determined as being frail with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function.

Another aspect provides a method of identifying subjects who will have improved survival outcomes when treated with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function; comprising the steps of

• • a) determining the overall biosignature score p; and
  • b) determining the subject as being frail if the score p is 0.15 to 0.56;
    • wherein the score p is determined by
      • i) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • • or
      • ii) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and log₁₀-transformed serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=-25.54+\left(-0.95\times \mathrm{sex}\right)+\left(0.10\times \mathrm{age}\right)+\left(1.20\times \mathrm{GDF}\text{-}15\right)$ $\left(+7.26\times \mathrm{Gln}\right)+\left(10.0\times \mathrm{albumin}\right)+\left(6.30\times \mathrm{GlycA}\right)+\left(-3.11\times \mathrm{phosphoglycerides}\right)+\left(3.22\times \mathrm{Gly}\right)+\left(-0.97\times \mathrm{Ala}\right).$

• • and
  • c) treating the subjects determined as being frail with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function.

Another aspect provides a method of identifying and treating subjects who will have improved survival outcomes when treated with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function; comprising the steps of

• • a) determining the overall biosignature score p; and
  • b) determining the subject as being frail if the score p is 0.15 to 0.56;
    • wherein the score p is determined by
      • i) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=\left(-9.31\pm 0.817\times \mathrm{sex}+0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}\text{-}15\right)$ $\left(+0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

• • • or
      • ii) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and log₁₀-transformed serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=-25.54+\left(-0.95\times \mathrm{sex}\right)+\left(0.10\times \mathrm{age}\right)+\left(1.20\times \mathrm{GDF}-15\right)+\left(7.26\times \mathrm{Gln}\right)+\left(10.0\times \mathrm{albumin}\right)+\left(6.30\times \mathrm{GlycA}\right)+\left(-3.11\times \mathrm{phosphoglycerides}\right)+\left(3.22\times \mathrm{Gly}\right)+\left(-0.97\times \mathrm{Ala}\right).$

• • and
  • c) treating the subjects determined as being frail with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function.

Another aspect provides a kit for evaluating frailty comprising

• • a) a test for measuring blood levels of GDF-15; and
  • b) optionally one or more tests for measuring blood levels of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine.

In some embodiments, the test for measuring albumin, glutamine, GlycA, and phosphoglyceride is the ¹H-NMR Nightingale system.

Another embodiment provides the use of tissue-specific blood biomarkers (e.g. NT-proBNP) to identify impaired organ or organ system (e.g. cardiac failure) as a subclassification (or subphenotyping) of frailty. In one embodiment, elevation of both circulating NT-proBNP and GDF-15 levels indicate CD and systemic tissue injury or hypoperfusion, and increase the probability of a diagnosis of heart failure and frailty (cardiac frailty). In another embodiment, sole elevation of NT-proBNP but not GDF-15 indicates cardiac dysfunction that is not so extensive as to cause systemic physiological compromise (cardiac dysfunction without frailty). In yet another embodiment, elevation of GDF-15 alone (with normal NT-proBNP levels) indicates systemic physiological injury, hypoperfusion or abnormalities that are less likely to be attributable cardiac dysfunction (noncardiac frailty). In some embodiments, GDF-15 elevation broadly indicates systemic tissue injury, inflammation, compromised systemic physiology and impaired physical fitness that characterize frailty (e.g. reduced skeletal muscle growth, weight loss, reduced appetite, easy fatigability).

In conjunction with physical measures (e.g. 6-minute walk distance (6MWD), gait speed, handgrip strength), GDF-15 is a useful biomarker for the classification and stratification of frailty classes.

In some embodiments, GDF-15 elevation is defined as having GDF-15 blood levels greater than 1000 pg/ml. In some embodiments, the GDF-15 blood levels are in a range between 1,000 to 6,000 pg/ml, 1000 to 4000 pg/ml, 2000 to 4000 pg/ml, 2500 to 3500 pg/ml, or 3000±1000 pg/ml. In some embodiments, the GDF-15 blood level is 3,206.6±2,565.4 pg/ml.

Examples

Provided herein are examples that describe in more detail certain embodiments of the present disclosure. The examples provided herein are merely for illustrative purposes and are not meant to limit the scope of the invention in any way. All references given below and elsewhere in the present application are hereby included by reference.

Example 1

Blood levels of a number of biomarkers and metabolites were measured in 306 subjects (derivation set). Blood serum levels of GDF-15 and NT-proBNP were measured using the Roche ELECSYS® GDF-15 Assay kit and a Roche COBAS® e immunoassay analyzer, or a compatible instrument, as per manufacturer.

Subjects were also evaluated based on the FRAIL Scale [Abelian van Kan 2008; Morley 2012; Woo 2012]. The 5-point FRAIL scale is a multi-domain instrument that assesses the key deficits and risks associated with frailty. A subject is frail if the score is 3 to 5; pre-frail if the score is 1 to 2; and robust if the score is 0.

It shall be understood that frailty severity can be defined by many different types of scores or methods, and there are other known frailty scoring methods that could stand in the place of the FRAIL scale, such as the Edmonton frail scale [Rolfson 2006]), or a cumulative deficit approach whereby an index is calculated from the proportion of health and medical problems relative to a predefined inventory (e.g. Rockwood frailty index)[Mitnitski 2002; Rockwood 2011].

Logistic regression analysis was done with adjustments for age and sex. Biomarker levels were expressed as mean±standard deviation (SD). Kruskal-Wallis H test with Dunn post hoc test, Chi-square or Fisher's exact test were used to compare differences between groups. ^aP<0.05, pre-frail vs. robust; ^bP<0.05, frail vs. robust; ^cP<0.05, frail vs. pre-frail (Table 2). The workflow of age- and sex-adjusted linear regression is shown in FIG. 7. The continuous variable of log₁₀-transformed NT-proBNP or GDF-15 level, was modeled on each (transformed) metabolite or metabolic feature as the dependent variable.

GDF-15 as an Indicator of Frailty

Table 2 shows that circulating blood levels of the biomarkers, NT-proBNP and GDF-15, can indicate non-frailty and frailty irrespective of the etiology. Table 2 also shows that subjects with GDF-15 blood levels in the range of 3,206.6±2,565.4 pg/ml were confirmed frail according to the FRAIL scale.

TABLE 2
Variables	Robust	Pre-frail	Frail	Overall
Sample size, n	104	107	95	306
NT-proBNP, pg/ml	180.8 ± 506.1	239.4 ± 466.4a	361.0 ± 745.5b,c	257.2 ± 582.1
GDF-15, pg/ml	1,667.4 ± 1,114.9	2,220.0 ± 1,781.3a	3,206.6 ± 2.565.4b,c	2.338.5 ± 1,986.0

GDF-15 Surprisingly Effective as a Differentiator of Frailty Vs. Non-Frailty

Table 3 shows that log₁₀-transformed GDF-15 does predict and differentiate frailty from non-frailty (P=1.29×10⁻³) whereas NT-proBNP does not (P=not significant (NS)). NT-proBNP is a strong independent predictor of CD, whereas GDF-15 can independently differentiate between individuals with and without frailty.

	TABLE 3
	Log10 NT-proBNP	Log10 GDF-15
Comparisons	OR	(95% CI)	P	OR	(95% CI)	P
Frailty vs. non-	1.07	(0.95-1.20)	NS	1.38	(1.13-1.67)	1.29 × 10−3
frailty
CD vs. non-CD	1.47	(1.33-1.62)	5.49 × 10−13	1.02	(0.85-1.23)	NS

Comparison Data: GDF-15 vs. NT-proBNP in Prediction of Frailty & CD

Table 4 shows multiple linear regression analysis of phenotypic variables modeling on log₁₀ NT-proBNP and log₁₀ GDF-15 levels as dependent variables identifying CD and frailty as their respective explanatory factors. Table 4 further confirms that elevated GDF-15 levels are predictive of subjects with CD and frailty.

TABLE 4
Independent	Log10 NT-proBNP	Log10 GDF-15
variables	β	SE	t	P-values	β	SE	t	P-values
Age, y	0.02	0.00	7.27	3.23 × 10−12	0.01	0.00	7.33	2.18 × 10−12
Sex, % female	−0.03	0.05	−0.65	NS	0.02	0.03	0.49	NS
BMI	0.00	0.01	0.05	NS	0.01	0.00	1.94	NS
Frailty status	0.05	0.03	1.47	NS	0.07	0.02	3.38	8.36 × 10−4
CD	0.41	0.06	7.37	1.71 × 10−12	−0.01	0.03	−0.22	NS
R2	0.39	0.27
BMI, body mass index;
CD, cardiac dysfunction;
GDF-15, growth differentiation factor 15;
NS, not significant;
NT-proBNP, N-terminal prohormone of B-type natriuretic peptide;
SE, standard error

NT-proBNP

FIG. 1 shows how NT-proBNP independently distinguishes older adults with and without CD (n=306 subjects). Adding additional variables including frailty (FRAIL score) and/or GDF-15 did not further improve the predictive performance of NT-proBNP for CD. DeLong test was used to test for statistical difference between classifiers.

FIGS. 2A-J show metabolomic biosignatures of NT-proBNP generated using linear regression for all 250 metabolites/metabolic features and the strength of the association between NT-proBNP and the metabolites measured using the β coefficient values. Individuals with CD and without CD (non-CD) were classified according to whether or not echocardiographic CD was present. Metabolomic biosignature of NT-proBNP classified according to whether or not echocardiographic CD is present. Linear regression with adjustment for age and sex was used to estimate the strength of association (β coefficient) between each metabolite/metabolic feature and NT-proBNP in non-CD and CD groups. Refer to Table 8 for identity of metabolite number.

Pairwise Comparisons without GDF-15 Guidance Leads to Weaker Predictive Abilities

FIGS. 3A-J show that without biomarker guidance, pairwise comparisons between frail and non-frail groups (frail vs. robust; pre-frail vs. robust; frail vs. pre-frail) are possible. In FIGS. 3A-J, logistic regression with adjustment for age and sex is used to model each metabolite/metabolic feature on frailty status. Odds ratios are used to estimate the direction, size, and strength of the association between the metabolite/metabolic feature and the frailty or non-frailty phenotype. No biomarker is used in this analysis. Statistically significant variables are highlighted in blue. Refer to Table 8 for identity of metabolite number.

FIGS. 4A(i)-4A(x), FIGS. 4B(i)-4B(x) and FIGS. 4C(i)-4C(x) show the metabolomic biosignature of GDF-15 classified according to frailty status (robust, pre-frail or frail). The metabolomic biosignature of GDF-15 was generated using linear regression for all 250 metabolites/metabolic features (see Table 8 for metabolites). Linear regression with adjustment for age and sex was used to estimate the strength of association 03 coefficient) between each metabolite/metabolic feature and GDF-15 in robust, pre-frail or frail groups. β coefficient values were calculated from correlating each metabolite/metabolic feature against its respective GDF-15 level. Refer to Table 8 for identity of metabolite number. Of note, the GDF-15-guided metabolomic biosignature for the robust and pre-frail (collectively, non-frail) groups are not markedly similar, whereas a plethora of statistically different metabolites/metabolic features highlighted as shown is evident. At the individual metabolite/metabolic feature level, the identities are shown in Table 6.

TABLE 6
Frailty-related metabolic biosignatures in different studies.[Fung 2018; Pujos-Guillot 2018; Marron 2019],
	NU-AGE study	Health ABC study	UFO study
	Study population
	Community-dwelling black	Community-dwelling elderly
	Free-living elderly in Europe	men in America	in HK (China)
	Frailty assessment
	Fried et al. (2001)	SAVE score	FRAIL score
	Subgroups
					Vigorous	Average	Frail
	Robust	Pre-frail	Robust	Pre-frail	(range:	(range:	(range:
	male	male	female	female	0-3)	4-5)	6-10)	Robust	Pre-frail	Frail
Sample size	60	31	67	54	73	105	109	104	107	95
Age, y	71 ± 4	73 ± 4	71 ± 4	72 ± 4	74 ± 3	75 ± 3	75 ± 3	71 ± 6	74 ± 8	79 ± 8
Sex, % female	0	0	100	100	0	0	0	42	81	84
Metabolomics	UPLC coupled to QTOF-MS	LC-MS	1H-NMR
platform
Blood sample	Serum	Overnight-fasting plasma	Non-fasting serum
types
Significant	Significant metabolites for pre-frailty	8 metabolites positively correlated	Compared with robust, the frail group:
metabolites or	at baseline in males (stable):	with SAVE scores:	Total concentration of lipoprotein
metabolic	Pipecolic acid ↑	Glucoronate	particles↑
features	2,3-dihydromethylpyrrole ↑	N-carbamoyl-beta-alanine	Phosphoglycerides ↑
	Proline ↑	Isocitrate	Cholines ↑
	Butyrylcarnitine ↑	Creatinine	Phosphatidylcholines ↑
	Significant metabolites for pre-frailty at	C4—OH carnitine	Sphingomyelins ↑
	baseline in females (stable):	Cystathionine	Docosahexaenoic acid ↑
	Amino-octanoic acid ↓	Hydroxyphenylacetate	Alanine ↑
	Significant metabolites for pre-frailty at	Putrescine	Glutamine ↑
	baseline in males (improved):	6 metabolites negatively correlated	Glycerol ↑
	Glutamine ↑	with SAVE scores:	Creatinine ↑
	Mannose ↓	Tryptophan	Albumin ↑
	Gly-Phe ↓	Methionine	GlycA ↑
	Significant metabolites for pre-frailty at	Tyrosine	Concentrations of particles in the
	baseline in females (improved):	C14:0 sphingomyelin	S_HDL ↑
	Threonine ↑	1-methylnicotinamide	Concentrations of free cholesterol in
	Fructose ↓	asparagine	the S_HDL ↑
	Phenylalanine ↓		Ratio of cholesterol to total lipids
			in S_LDL ↑
			Ratio of cholesterol esters to total
			lipids in XL_HDL ↑
			Ratio of free cholesterol to total
			lipids in XL_HDL ↓
			Ratio of phospholipids to total lipids
			in M_HDL ↓
1H-NMR, proton nuclear magnetic resonance;
LC-MS, liquid chromatography-mass spectrometry;
QTOF-MS, quadrupole time-of-flight mass spectrometry;
UPLC, ultra-performance liquid chromatography

GDF-15 Predictive of Reduced Physical Activity

Table 5 below shows how NT-proBNP or GDF-15 levels impact other physical fitness measures (recognized surrogate markers of frailty and physical fitness) using Spearman's test with adjustment for age and sex. Both NT-proBNP or GDF-15 are markers of functional and physical domains of frailty. The data show that GDF-15 is significantly and inversely correlated with physical fitness and strength.

GDF-15 Guided Metabolomic Signature Most Predictive of Frailty

FIGS. 5A-B show the validation of the combined classifier of metabolites/metabolic features (albumin, glutamine, and glycoprotein actetylation marker of inflammation (GlycA) [Bell 1987; Otyos 2015; Ritchie 2015] that met the FDR 5% (from 4A(i)-4A(x), 4B(i)-4B(x) and 4C(i)-4C(x)) with addition of phosphoglycerides (Table 7), age, sex and GDF-15 to demonstrate an excellent predictive capacity of AUC 0.841 for prediction of frailty against non-frailty.

FIG. 6 shows a workflow of logistic regression analysis with adjustment for age and sex. A binary variable is modelled on each (transformed) metabolite or metabolic feature as the dependent variable.

	TABLE 5
	Model with adjustment for age and sex
Physical fitness	NT-proBNP		GDF-15
measures	Rho	P	Rho	P
6-minute walk	−0.13	0.02	−0.29	4.71 &times 10−7
distance
Gait speed	−0.10	NS	−0.26	3.14 &times 10−6
HGS/BMI	−0.06	NS	−0.20	3.80 &times 10−4
HGS/BMI, handgrip strength indexed to body mass index;
NS, not significant.

Example 2: Metabolic Profiling

Metabolomic profiling of blood samples from 306 subjects was done using ¹H-NMR (Nightingale Health Ltd (Helsinki, Finland) [Soininen P, et al. Circ Cardiovasc Genet 2015; 8:192-206]). Table 8 shows the biomarkers profiled. Fresh blood serum or newly thawed specimens retrieved from −80° C. storage (or in transit on dry ice) were processed on the Nightingale proprietary platform and a proprietary Nightingale algorithm was used to identify and quantify levels of GlycA, phosphoglycerides, albumin and glutamine based on ¹H-NMR spectral data.

Univariate regression, adjusted logistic (FIG. 6) and linear regression analyses (FIG. 7) was done to identify associations represented by β values between the biomarker (e.g. NT-proBNP, GDF-15) and each metabolite/metabolic feature and the dependent variable for the different clinical phenotypes or subphenotypes under study (FIGS. 2A-J, 3A-J, 4A(i)-4A(x), 4B(i)-4B(x) and 4C(i)-4C(x)).

A series of biosignatures were generated for each group or subgroup using a biomarker-guided metabolomic profiling strategy (FIGS. 6-7 and Table 7), to show the significant correlations 03 values) between the biomarker and the metabolites/metabolic feature (FIGS. 2A-J, 3A-J, 4A(i)-4A(x), 4B(i)-4B(x) and 4C(i)-4C(x)). The differences in the patterns of each group's metabolome can be visualized in a forest plot and the statistically significant findings are highlighted in the respective figures for the particular metabolites/metabolic features that reach the stringent false discovery rate (FDR) cut-off of 0.05 (5%).

Table 7 below shows how subjects who had GDF-15 levels that highly correlated with the following three or six biomarkers also showed the phenotype of frailty according to the FRAIL scale. Significant metabolites/metabolic features and area under the receiver operating curve (AUC) values at the respective false-discovery rates (FDR) are shown. Incremental lowering of the FDR threshold from 0.05 (standard) to 0.135 and beyond yields a greater number of metabolites/metabolic features.

TABLE 7
	Significant metabolic features (along with age,
FDR	sex, GDF-15)	AUC
0.05	Albumin, Gln, GlycA	0.8181
0.075	Albumin, Gln, GlycA	0.8181
0.1	Albumin, Gln, GlycA	0.8181
0.125	Albumin, Gln, GlycA	0.8181
0.135	Albumin, Gln, GlycA, Phosphoglycerides, Gly, Ala	0.8438
0.15	Albumin, Gln, GlycA, Phosphoglycerides, Gly, Ala	0.8438
0.175	Albumin, Gln, GlycA, Phosphoglycerides, Gly, Ala	0.8438
0.2	Albumin, Gln, GlycA, Phosphoglycerides, Gly, Ala	0.8438

Table 8 shows a list of 250 metabolites/metabolic features analyzed by Nightingale's ¹H-NMR platform.

TABLE 8
No.		Units
	CHOLESTEROL
001	Total cholesterol	mmol/l
002	Total cholesterol minus HDL-C	mmol/l
003	Remnant cholesterol (non-HDL, non-LDL-cholesterol)	mmol/l
004	VLDL cholesterol	mmol/l
005	Clinical LDL cholesterol	mmol/l
006	LDL cholesterol	mmol/l
007	HDL cholesterol	mmol/l
	TRIGLYCERIDES
008	Total triglycerides	mmol/l
009	Triglycerides in VLDL	mmol/l
010	Triglycerides in LDL	mmol/l
011	Triglycerides in HDL	mmol/l
	PHOSPHOLIPIDS
012	Total phospholipids in lipoprotein particles	mmol/l
013	Phospholipids in VLDL	mmol/l
014	Phospholipids in LDL	mmol/l
015	Phospholipids in HDL	mmol/l
	CHOLSTERYL ESTERS
016	Total esterified cholesterol	mmol/l
017	Cholesteryl esters in VLDL	mmol/l
018	Cholesteryl esters in LDL	mmol/l
019	Cholesteryl esters in HDL	mmol/l
	FREE CHOLESTEROL
020	Total free cholesterol	mmol/l
021	Free cholesterol in VLDL	mmol/l
022	Free cholesterol in LDL	mmol/l
023	Free cholesterol in HDL	mmol/l
	TOTAL LIPIDS
024	Total lipids in lipoprotein particles	mmol/l
025	Total lipids in VLDL	mmol/l
026	Total lipids in LDL	mmol/l
027	Total lipids in HDL	mmol/l
	LIPOPROTEIN PARTICLE CONCENTRATIONS
028	Total concentration of lipoprotein particles	mmol/l
029	Concentration of VLDL particles	mmol/l
030	Concentration of LDL particles	mmol/l
031	Concentration of HDL particles	mmol/l
	LIPOPROTEIN PARTICLE SIZES
032	Average diameter for VLDL particles	nm
033	Average diameter for LDL particles	nm
034	Average diameter for HDL particles	nm
035	Phosphoglycerides	mmol/l
036	Ratio of triglycerides to phosphoglycerides	ratio (%)
037	Total cholines	mmol/l
038	Phosphatidylcholines	mmol/l
039	Sphingomyelins	mmol/l
	APOLIPOPROTEINS
040	Apolipoprotein B	g/l
041	Apoliproprotein A1	g/l
042	Ratio of apolipoprotein B to apolipoprotein A1	ratio (%)
	FATTY ACIDS
043	Total fatty acids	mmol/l
044	Degree of unsaturation	degree
045	Omega-3 fatty acids	mmol/l
046	Omega-6 fatty acids	mmol/l
047	Polyunsaturated fatty acids	mmol/l
048	Monosaturated fatty acids	mmol/l
049	Saturated fatty acids	mmol/l
050	Linoleic acid	mmol/l
051	Docosahexaenoic acid	mmol/l
	FATTY ACID RATIOS
052	Ratio of omega-3 fatty acids to total fatty acids	ratio (%)
053	Ratio of omega-6 fatty acids to total fatty acids	ratio (%)
054	Ratio of polyunsaturated fatty acids to total fatty acids	ratio (%)
055	Ratio of monounsaturated fatty acids to total fatty acids	ratio (%)
056	Ratio of saturated fatty acids to total fatty acids	ratio (%)
057	Ratio of linoleic acid to total fatty acids	ratio (%)
058	Ratio of docosahexaenoic acid to total fatty acids	ratio (%)
059	Ratio of polyunsaturated fatty acids to monosaturated	ratio (%)
	fatty acids
060	Ratio of omega-6 fatty acids to omega-3 fatty acids	ratio (%)
	AMINO ACIDS
061	Alanine	mmol/l
062	Glutamine	mmol/l
063	Glycine	mmol/l
064	Histidine	mmol/l
	BRANCHED-CHAIN AMINO ACIDS
065	Total concentration of branched-chain amino acids	mmol/l
066	Isoleucine	mmol/l
067	Leucine	mmol/l
068	Valine	mmol/l
	AROMATIC AMINO ACIDS
069	Phenylalanine	mmol/l
070	Tyrosine	mmol/l
	GLYCOLYSIS-RELATED METABOLITES
071	Glucose	mmol/l
072	Lactate	mmol/l
073	Pyruvate	mmol/l
074	Citrate	mmol/l
075	Glycerol	mmol/l
	KETONE BODIES
076	3-Hydroxybutyrate	mmol/l
077	Acetate	mmol/l
078	Acetoacetate	mmol/l
079	Acetone	mmol/l
	FLUID BALANCE
080	Creatinine	mmol/l
081	Albumin	g/l
	INFLAMMATION
082	Glycoprotein acetyls	mmol/l
	LIPOPROTEIN SUBCLASSES
	Chylomicrons and extremely large VLDL (diameter 75 nm
	upwards)
083	Concentrations of chylomicron and extremely large VLDL	mmol/l
	particles
084	Total lipids in chylomicron and extremely large VLDL	mmol/l
085	Phospholipids in chylomicrons and extremely large VLDL	mmol/l
086	Cholesterol in chylomicrons and extremely large VLDL	mmol/l
087	Cholesteryl esters in chylomicrons and extremely large VLDL	mmol/l
088	Free cholesterol in chylomicrons and extremely large VLDL	mmol/l
089	Triglycerides in chylomicrons and extremely large VLDL	mmol/l
	Very large VLDL (average diameter 64 nm)
090	Concentration of very large VLDL particles	mmol/l
091	Total lipids in very large VLDL	mmol/l
092	Phospholipids in very large VLDL	mmol/l
093	Cholesterol in very large VLDL	mmol/l
094	Cholesteryl esters in very large VLDL	mmol/l
095	Free cholesterol in very large VLDL	mmol/l
096	Triglycerides in very large VLDL	mmol/l
	Large VLDL (average diameter 53.6 nm)
097	Concentration of large VLDL particles	mmol/l
098	Total lipids in large VLDL	mmol/l
099	Phospholipids in large VLDL	mmol/l
100	Cholesterol in large VLDL	mmol/l
101	Cholesteryl esters in large VLDL	mmol/l
102	Free cholesterol in large VLDL	mmol/l
103	Triglycerides in large VLDL	mmol/l
	Medium VLDL (average diameter 44.5 nm)
104	Concentration of medium VLDL particles	mmol/l
105	Total lipids in medium VLDL	mmol/l
106	Phospholipids in medium VLDL	mmol/l
107	Cholesterol in medium VLDL	mmol/l
108	Cholesteryl esters in medium VLDL	mmol/l
109	Free cholesterol in medium VLDL	mmol/l
110	Triglycerides in medium VLDL	mmol/l
	Small VLDL (average diameter 36.8 nm)
111	Concentration of small VLDL particles	mmol/l
112	Total lipids in small VLDL	mmol/l
113	Phospholipids in small VLDL	mmol/l
114	Cholesterol in small VLDL	mmol/l
115	Cholesteryl esters in small VLDL	mmol/l
116	Free cholesterol in small VLDL	mmol/l
117	Triglycerides in small VLDL	mmol/l
	Very small VLDL (average diameter 31.3 nm)
118	Concentration of small VLDL particles	mmol/l
119	Total lipids in small VLDL	mmol/l
120	Phospholipids in small VLDL	mmol/l
121	Cholesterol in small VLDL	mmol/l
122	Cholesteryl esters in small VLDL	mmol/l
123	Free cholesterol in small VLDL	mmol/l
124	Triglycerides in small VLDL	mmol/l
	IDL (average diameter 28.6 nm)
125	Concentration of IDL particles	mmol/l
126	Total lipids in IDL	mmol/l
127	Phospholipids in IDL	mmol/l
128	Cholesterol in IDL	mmol/l
129	Cholesteryl esters in IDL	mmol/l
130	Free cholesterol in IDL	mmol/l
131	Triglycerides in IDL	mmol/l
	Large LDL (average diameter 25.5 nm)
132	Concentration of large LDL particles	mmol/l
133	Total lipids in large LDL	mmol/l
134	Phospholipids in large LDL	mmol/l
135	Cholesterol in large LDL	mmol/l
136	Cholesteryl esters in large LDL	mmol/l
137	Free cholesterol in large LDL	mmol/l
138	Triglycerides in large LDL	mmol/l
	Medium LDL (average diameter 23 nm)
139	Concentration of medium LDL particles	mmol/l
140	Total lipids in medium LDL	mmol/l
141	Phospholipids in medium LDL	mmol/l
142	Cholesterol in medium LDL	mmol/l
143	Cholesteryl esters in medium LDL	mmol/l
144	Free cholesterol in medium LDL	mmol/l
145	Triglycerides in medium LDL	mmol/l
	Small LDL (average diameter 18.7 nm)
146	Concentration of small LDL particles	mmol/l
147	Total lipids in small LDL	mmol/l
148	Phospholipids in small LDL	mmol/l
149	Cholesterol in small LDL	mmol/l
150	Cholesteryl esters in small LDL	mmol/l
151	Free cholesterol in small LDL	mmol/l
152	Triglycerides in small LDL	mmol/l
	Very large HDL (average diameter 14.3 nm)
153	Concentration of very large HDL particles	mmol/l
154	Total lipids in very large HDL	mmol/l
155	Phospholipids in very large HDL	mmol/l
156	Cholesterol in very large HDL	mmol/l
157	Cholesteryl esters in very large HDL	mmol/l
158	Free cholesterol in very large HDL	mmol/l
159	Triglycerides in very large HDL	mmol/l
	Large HDL (average diameter 12.1 nm)
160	Concentration of large HDL particles	mmol/l
161	Total lipids in large HDL	mmol/l
162	Phospholipids in large HDL	mmol/l
163	Cholesterol in large HDL	mmol/l
164	Cholesteryl esters in large HDL	mmol/l
165	Free cholesterol in large HDL	mmol/l
166	Triglycerides in large HDL	mmol/l
	Medium HDL (average diameter 10.9 nm)
167	Concentration of large HDL particles	mmol/l
168	Total lipids in large HDL	mmol/l
169	Phospholipids in large HDL	mmol/l
170	Cholesterol in large HDL	mmol/l
171	Cholesteryl esters in large HDL	mmol/l
172	Free cholesterol in large HDL	mmol/l
173	Triglycerides in large HDL	mmol/l
	Small HDL (average diameter 8.7 nm)
174	Concentration of small HDL particles	mmol/l
175	Total lipids in small HDL	mmol/l
176	Phospholipids in small HDL	mmol/l
177	Cholesterol in small HDL	mmol/l
178	Cholesteryl esters in small HDL	mmol/l
179	Free cholesterol in small HDL	mmol/l
180	Triglycerides in small HDL	mmol/l
	RELATIVE LIPOPROTEIN LIPID CONCENTRATIONS
	Chylomicrons and extremely large VLDL ratios
181	Phospholipids to total lipids ratio in chylomicrons and	ratio (%)
	extremely large VLDL
182	Cholesterol to total lipids ratio in chylomicrons and	ratio (%)
	extremely large VLDL
183	Cholesteryl esters to total lipids ratio in chylomicrons and	ratio (%)
	extremely large VLDL
184	Free cholesterol to total lipids ratio in chylomicrons and	ratio (%)
	extremely large VLDL
185	Triglycerides to total lipids ratio in chylomicrons and	ratio (%)
	extremely large VLDL
	Very large VLDL ratios
186	Phospholipids to total lipids ratio in very large VLDL	ratio (%)
187	Cholesterol to total lipids ratio in very large VLDL	ratio (%)
188	Cholesteryl esters to total lipids ratio in very large VLDL	ratio (%)
189	Free cholesterol to total lipids ratio in very large VLDL	ratio (%)
190	Triglycerides to total lipids ratio in very large VLDL	ratio (%)
	Large VLDL ratios
191	Phospholipids to total lipids ratio in large VLDL	ratio (%)
192	Cholesterol to total lipids ratio in large VLDL	ratio (%)
193	Cholesteryl esters to total lipids ratio in large VLDL	ratio (%)
194	Free cholesterol to total lipids ratio in large VLDL	ratio (%)
195	Triglycerides to total lipids ratio in large VLDL	ratio (%)
	Medium VLDL ratios
196	Phospholipids to total lipids ratio in medium VLDL	ratio (%)
197	Cholesterol to total lipids ratio in medium VLDL	ratio (%)
198	Cholesteryl esters to total lipids ratio in medium VLDL	ratio (%)
199	Free cholesterol to total lipids ratio in medium VLDL	ratio (%)
200	Triglycerides to total lipids ratio in medium VLDL	ratio (%)
	Small VLDL ratios
201	Phospholipids to total lipids ratio in small VLDL	ratio (%)
202	Cholesterol to total lipids ratio in small VLDL	ratio (%)
203	Cholesteryl esters to total lipids ratio in small VLDL	ratio (%)
204	Free cholesterol to total lipids ratio in small VLDL	ratio (%)
205	Triglycerides to total lipids ratio in small VLDL	ratio (%)
	Very small VLDL ratios
206	Phospholipids to total lipids ratio in very small VLDL	ratio (%)
207	Cholesterol to total lipids ratio in very small VLDL	ratio (%)
208	Cholesteryl esters to total lipids ratio in very small VLDL	ratio (%)
209	Free cholesterol to total lipids ratio in very small VLDL	ratio (%)
210	Triglycerides to total lipids ratio in very small VLDL	ratio (%)
	IDL ratios
211	Phospholipids to total lipids ratio in IDL	ratio (%)
212	Cholesterol to total lipids ratio in IDL	ratio (%)
213	Cholesteryl esters to total lipids ratio in IDL	ratio (%)
214	Free cholesterol to total lipids ratio in IDL	ratio (%)
215	Triglycerides to total lipids ratio in IDL	ratio (%)
	Large LDL ratios
216	Phospholipids to total lipids ratio in large LDL	ratio (%)
217	Cholesterol to total lipids ratio in large LDL	ratio (%)
218	Cholesteryl esters to total lipids ratio in large LDL	ratio (%)
219	Free cholesterol to total lipids ratio in large LDL	ratio (%)
220	Triglycerides to total lipids ratio in large LDL	ratio (%)
	Medium LDL ratios
221	Phospholipids to total lipids ratio in medium VLDL	ratio (%)
222	Cholesterol to total lipids ratio in medium VLDL	ratio (%)
223	Cholesteryl esters to total lipids ratio in medium VLDL	ratio (%)
224	Free cholesterol to total lipids ratio in medium VLDL	ratio (%)
225	Triglycerides to total lipids ratio in medium VLDL	ratio (%)
	Small LDL ratios
226	Phospholipids to total lipids ratio in small LDL	ratio (%)
227	Cholesterol to total lipids ratio in small LDL	ratio (%)
228	Cholesteryl esters to total lipids ratio in small LDL	ratio (%)
229	Free cholesterol to total lipids ratio in small LDL	ratio (%)
230	Triglycerides to total lipids ratio in small LDL	ratio (%)
	Very large HDL ratios
231	Phospholipids to total lipids ratio in very large HDL	ratio (%)
232	Cholesterol to total lipids ratio in very large HDL	ratio (%)
233	Cholesteryl esters to total lipids ratio in very large HDL	ratio (%)
234	Free cholesterol to total lipids ratio in very large HDL	ratio (%)
235	Triglycerides to total lipids ratio in very large HDL	ratio (%)
	Large HDL ratios
286	Phospholipids to total lipids ratio in large HDL	ratio (%)
237	Cholesterol to total lipids ratio in large HDL	ratio (%)
238	Cholesteryl esters to total lipids ratio in large HDL	ratio (%)
239	Free cholesterol to total lipids ratio in large HDL	ratio (%)
240	Triglycerides to total lipids ratio in large HDL	ratio (%)
	Medium HDL ratios
241	Phospholipids to total lipids ratio in medium HDL	ratio (%)
242	Cholesterol to total lipids ratio in medium HDL	ratio (%)
243	Cholesteryl esters to total lipids ratio in medium HDL	ratio (%)
244	Free cholesterol to total lipids ratio in medium HDL	ratio (%)
245	Triglycerides to total lipids ratio in medium HDL	ratio (%)
	Small HDL ratios
246	Phospholipids to total lipids ratio in small HDL	ratio (%)
247	Cholesterol to total lipids ratio in small HDL	ratio (%)
248	Cholesteryl esters to total lipids ratio in small HDL	ratio (%)
249	Free cholesterol to total lipids ratio in small HDL	ratio (%)
250	Triglycerides to total lipids ratio in small HDL	ratio (%)

Numbered Embodiments

• 1. A method of determining frailty severity in a subject comprising the steps of
  • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) determining the subject as being frail if the level of the biomarker in the biological sample is higher than about 2,000 pg/ml to 6,000 pg/ml; pre-FRAIL if the level of the biomarker in the biological sample is higher than 500 pg/ml to 2000 pg/ml; and robust if the level of the biomarker in the biological sample is less than 500 pg/ml.
• 2. A method of determining frailty severity in a subject comprising the steps of
  • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;
  • c) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=\exp \left(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+0.000121\times \mathrm{GDF}\text{-}15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

and

• • d) determining the subject as being frail if the score p is a value defined by a threshold value in Table 1 wherein the corresponding sensitivity and specificity values of the threshold value add up to between 1.4 and 1.6; and wherein at least one of the sensitivity or specificity values is 0.5 or above.
• 3. The method of embodiment 2, wherein the score p is 0.15 to 0.56.
• 4. The method of embodiment 3, wherein the score p is 0.259 or a threshold value with the maximum value of Youden's J statistic according to Table 1.
• 5. The method of embodiment 4, wherein the maximum value of Youden's J statistic is 0.553.
• 6. The method of any one of embodiments 1-4, wherein if the subject is determined to be frail, treating the subject with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function.
• 7. The method of embodiment 5, wherein the therapeutic drug is sacubitril/valsartan, dapagliflozin, empagliflozin, beta blocker (e.g. metoprolol, carvedilol, bisoprolol), renin-angiotensin system inhibitor (e.g. enalapril, lisinopril), mineralocorticoid receptor antagonist (e.g. eplerenone, spironolactone), ivabradine, digoxin, inotropes (e.g. dobutamine, milrinone) or inodilator (e.g. levosimendan).
• 8. The method of any one of embodiments 1-7, wherein the method is an in vitro method.
• 9. A method of determining frailty severity in a subject comprising the steps of
  • a) measuring the levels of GDF-15 in a biological sample from the subject; and
  • b) measuring the levels of NT-proBNP, wherein if NT-proBNP levels are elevated but GDF-15 levels are not, determining the subject has cardiac dysfunction without frailty; if GDF-15 levels are elevated but NT-proBNP are not, determining the subject has systemic physiological injury, hypoperfusion, diabetes mellitus, inflammatory disorders, or non-cardiac frailty; if both GDF-15 and NT-proBNP levels are elevated, determining the subject has frailty and is predicted to have heart failure and if neither NT-proBNP levels nor GDF-15 levels are elevated, determining the subject is at low risk for frailty and low risk for heart failure.
• 10. The method of embodiment 9, further comprising the step of treating the subject with guideline-directed medical therapy (GDMT); wherein if the subject has elevated levels of both NT-proBNP and GDF-15, treating the subject as advanced stage Din accordance with GDMT; if the subject has elevated levels of NT-proBNP but not elevated levels of GDF-15, conducting cardiac imaging to determine the causes of cardiac dysfunction and treating the cardiac dysfunction in accordance with stage B or C in accordance with GDMT; if the subject has elevated levels of GDF-15 but not elevated levels of NT-proBNP, conducting a clinical assessment of medical comorbidities and treating the subject in accordance with stage B or C in accordance with GDMT; and if the subject does not have elevated levels of either NT-proBNP or GDF-15, treating the patient with as stage A in accordance with GDMT.
• 11. A method of identifying and treating frailty, altered physiological and physical reserve, aging, or aging-related inflammation in a subject comprising the steps of
  • a) measuring the levels of GDF-15 in a biological sample from the subject;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;
  • c) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=\exp (-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}\text{-}15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

and

• • d) determining the subject as being frail if the score p is 0.15 to 0.56.
• 12. A system for detecting frailty in a subject comprising:
  • a) a GDF-15 analyzer configured to analyze biological samples from the subject to provide a concentration of GDF-15 in the biological sample;
  • b) a computer programmed to execute the following steps:
    • i) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=\exp (-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}\text{-}15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

and

• • • ii) determining the subject as being frail if the score p is 0.15 to 0.56.
• 13. A method of improving the accuracy of frailty and non-frailty classification comprising using GDF-15 as a guiding biomarker with a metabolomic panel of metabolites selected from one or more of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine; comprising the following steps:
  • a) measuring GDF-15 concentration in a blood serum or plasma sample from a subject using the Roche Elecsys Assay kit on a Roche Cobas e immunoassay analyzer;
  • b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine using ¹H-NMR Nightingale metabolomic profiling;
  • c) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=\exp (-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}\text{-}15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycaA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+\left(0.266\times \mathrm{Gly}\right)+\left(-0.0577\times \mathrm{Ala}\right);$

and

• • d) determining the subject as being frail if the score p is 0.15 to 0.56.
• 14. A method of identifying subjects who will have improved survival outcomes when treated with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function; comprising the steps of
  • a) determining the overall biosignature score p by inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

$p=\frac{\exp \left(H\right)}{1+\exp \left(H\right)}$ $\mathrm{wherein}$ $H=\exp \left(-9.31\pm 0.817\times \mathrm{sex}+\left(0.111\times \mathrm{age}\right)+\left(0.000121\times \mathrm{GDF}-15\right)+\left(0.355\times \mathrm{Gln}\right)+\left(0.571\times \mathrm{albumin}\right)+\left(0.526\times \mathrm{GlycA}\right)+\left(-0.256\times \mathrm{phosphoglycerides}\right)+0.266\times \mathrm{Gly}\right)+\left(0.0577\times \mathrm{Ala}\right);$

• • b) determining the subject as being frail if the score p is 0.15 to 0.56; and
  • c) treating the subjects determined as being frail with exercise therapy, physical therapy, physiotherapy, nutritional supplementation (amino acid(s)/leucine (in non-cardiac failure)/protein), or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function.
• 15. A kit for evaluating frailty comprising
  • a) a test for measuring blood levels of GDF-15; and
  • b) optionally one or more tests for measuring blood levels of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine.
• 16. The kit of embodiment 15 wherein the test for measuring albumin, glutamine, GlycA, and phosphoglyceride is the ¹H-NMR Nightingale system.

The exemplary embodiments of the present invention are thus fully described. Although the description referred to particular embodiments, it will be clear to one skilled in the art that the present invention may be practiced with variation of these specific details. Hence this invention should not be construed as limited to the embodiments set forth herein.

Claims

1. A method of treating frailty in a subject comprising the steps of a) measuring the levels of GDF-15 in a biological sample from the subject; andb) determining the subject as being frail if the level of the biomarker in the biological sample is higher than about 2,000 pg/ml to 6,000 pg/ml; pre-frail if the level of the biomarker in the biological sample is higher than 500 pg/ml to 2000 pg/ml; and robust if the level of the biomarker in the biological sample is less than 500 pg/ml;wherein if the subject is determined to be frail, treating the subject.

2. A method of treating frailty in a subject comprising the steps of: a) measuring the levels of GDF-15 in a biological sample from the subject;b) measuring the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine;c) determining the overall biosignature score p; andd) determining the subject as being frail if p is Z; wherein Z is a value defined in Table 1 wherein the corresponding sensitivity and specificity values add up to between 1.4 and 1.5;wherein the score p is determined by i) inputting the subject's age in years; sex as value of 0 if female, 1 if male; and serum concentrations of biomarkers GDF-15 (pg/ml), albumin (g/1), glutamine (mmol/1), GlycA (mmol/1), phosphoglycerides (mmol/1), glycine (mmol/1), and alanine (mmol/1) of the subject into the following equation:

3. The method of claim 2, wherein Z is 0.15 to 0.56.

4. The method of claim 3, wherein Z is 0.259 or a threshold value with the maximum value of Youden's J statistic according to Table 1.

5. The method of claim 4, wherein the maximum value of Youden's J statistic is 0.553.

6. The method of claim 2, wherein treating the subject comprises exercise therapy, physical therapy, physiotherapy, nutritional supplementation, or administering a therapeutic drug for treating impaired cardiovascular or cardiopulmonary function.

7. The method of claim 6, wherein the therapeutic drug is sacubitril/valsartan, dapagliflozin, empagliflozin, beta blocker (e.g. metoprolol, carvedilol, bisoprolol), renin-angiotensin system inhibitor (e.g. enalapril, lisinopril), mineralocorticoid receptor antagonist (e.g. eplerenone, spironolactone), ivabradine, digoxin, inotropes (e.g. dobutamine, milrinone) or inodilator (e.g. levosimendan).

8. (canceled)

9. A method of treating frailty in a subject comprising the steps of a) measuring the levels of GDF-15 in a biological sample from the subject;b) measuring the levels of NT-proBNP,wherein if NT-proBNP levels are elevated but GDF-15 levels are not, determining the subject has cardiac dysfunction without frailty; if GDF-15 levels are elevated but NT-proBNP are not, determining the subject has systemic physiological injury, hypoperfusion, diabetes mellitus, inflammatory disorders, or non-cardiac frailty; if both GDF-15 and NT-proBNP levels are elevated, determining the subject has frailty and is predicted to have heart failure and if neither NT-proBNP levels nor GDF-15 levels are elevated, determining the subject is at low risk for frailty and low risk for heart failure; andc) treating the subject with a guideline-directed medical therapy (GDMT); wherein if the subject has elevated levels of both NT-proBNP and GDF-15, treating the subject as advanced stage D in accordance with GDMT; if the subject has elevated levels of NT-proBNP but not elevated levels of GDF-15, conducting cardiac imaging to determine the causes of cardiac dysfunction and treating the cardiac dysfunction in accordance with stage B or C in accordance with GDMT; if the subject has elevated levels of GDF-15 but not elevated levels of NT-proBNP, conducting a clinical assessment of medical comorbidities and treating the subject in accordance with stage B or C in accordance with GDMT; and if the subject does not have elevated levels of either NT-proBNP or GDF-15, treating the patient with as stage A in accordance with GDMT.

10-11. (canceled)

12. A system for detecting frailty in a subject comprising: a) a GDF-15 analyzer configured to analyze biological samples from the subject to provide a concentration of GDF-15 in the biological sample;b) a computer programmed to execute at least the steps i) and ii) of claim 2.

13. The method of claim 2, wherein a) the biological sample is a blood serum or plasma sample from a subject and is measured using the ROCHE Elecsys Assay kit on a ROCHE Cobas e immunoassay analyzer;b) the levels of one or more biomarkers selected from the group consisting of albumin, glutamine, GlycA, phosphoglycerides, glycine, and alanine are measured using 1H-NMR Nightingale metabolomic profiling.

14-16. (canceled)