1. Field of the Invention
The invention provides a method and system for providing quality assurance (QA) confirmation in real-time for solid phase immunoassay test results. The invention is particularly well-suited for use with automated test analysis instrumentation, such as readers and cameras, irrespective of instrument-to-instrument variation in illumination and optical quality.
2. Background Information
Immunoassay testing is a promising technology for detecting the presence of an analyte in a sample of biological fluid through the use of immunochemistry. One form of immunoassay testing includes immunochemical based test strips. Conventional test devices include detection zones in which a colored band appears (or is absent) when a specific analyte is present in a human fluid, such as detecting illicit drugs or substances. Conventional test devices provide home testing or convenient clinic-based testing.
However, many tests reveal false positives or false negatives due to a variety of factors, including the inability to discern the intensity of optical density revealed at one or more detection zones of the test device. Coupled with imperfections in manufacturing test strips and challenges in producing easily identifiable results, such errors make use of these strips less than ideal. Incorporation of mechanisms in immunoassay devices to provide quality assurance and reliability of test results would benefit the art.
The present invention provides a system and method for performing an immunoassay which utilize a test substrate (such as a nitrocellulose lateral flow immunoassay test strip) providing visually readable test results and having a QA label thereon, which label contains one or more stable optically detectable markers, such as colored lines of known density, adaptable to a plurality of test formats. Methods for use of the test substrates of the invention to improve test result reliability are also provided.
Accordingly, in one aspect, the present invention provides a method of performing an immunoassay. The method includes: a) contacting a lateral flow immunoassay device with a sample, wherein the device includes: i) a detection zone having an analyte binding site; and ii) a QA label having an optically detectable marker of a known density value; b) generating an optical image of the detection zone and the QA label; c) analyzing the image generated in (b) to determine a test density value of the optically detectable marker; d) comparing the test density value with the known density value; and e) analyzing the image generated in (b) to determine a density value of the detection zone when the test density value is within a preset deviation from the known density value.
In another aspect, the present invention provides a system for performing an immunoassay. The system includes: a) a lateral flow immunoassay device including i) a detection zone; and ii) a QA label having at least one optically detectable marker of a known density value; b) an optical image generator; c) a visual display; d) a processor comprising computer-executable instructions for: i) comparing the known density value with a test density value of the at least one optically detectable marker generated via the optical image generator; ii) determining whether the test density value is within a preset deviation of the known density value; and iii) determining the density value of the detection zone when the test density value is within the present deviation; and e) a memory for storage of data relating to one or more immunoassay devices.
The invention provides an in-test process, high quality QA confirmatory image for accurate analysis and consistent image capture. The invention comprises a test substrate (such as a nitrocellulose lateral flow immunoassay test strip) having a QA label thereon, which label contains at least one optically detectable marker including one or more stable colored lines of known density, adaptable to a plurality of test formats. Using an optical reader as an example of suitable instrumentation for use with the invention, the reader measures the density of this line with every scan and determines whether the density value as determined in a particular scan falls within an acceptable range as compared to the known density value. The QA label simultaneously determines whether critical operating parameters of the reader (such as lamp intensity, scanner calibration, and software algorithms) are performing within specifications. If a reading is outside the accepted range, a test result would be noted as invalid and corrective actions could be implemented.
With reference to
The use of reagent-impregnated test strips in specific binding assays, such as immunoassays, is well-known (see, e.g., U.S. Pat. No. 5,622,871, to May, et al., the text of which is incorporated herein by this reference). With reference to
A typical analytical test device comprises a hollow casing constructed of moisture-impervious solid material (which may be opaque or transparent, but will include visually readable portions at test and control zones) containing a dry porous carrier which communicates directly or indirectly with the exterior of the casing such that a liquid test sample can be applied to the porous carrier. A test device may incorporate a porous solid phase material carrying in a first zone, a labeled reagent which is retained in the first zone while the porous material is in the dry state but may be free to migrate through the porous material when the porous material is moistened, for example by the application of an aqueous liquid sample suspected of containing the analyte to the sample receiving zone (25). A second zone, spatially distinct from the first zone, may contain an unlabelled specific binding reagent having specificity for the analyte, and which is capable of participating with the labeled reagent in either a “sandwich” or a “competition” test reaction. Typically, the unlabeled specific binding reagent is immobilized on the porous material at the detection zone (15) such that it is not free to migrate when the porous material is in the moist state.
A standard image reader of an optical diagnostic system requires a consistent high quality image for accurate analysis and to ensure a consistent image capture, an in-process quality assurance (QA) system needs to be established. Analyte binding reagents are not present in the QA portion of devices produced and used according to the invention. As discussed above, the present QA approach is to attach a QA label of the present invention, which contains a stable colored line(s) of known density to every test format. As such, conveniently the QA portion of the invention is a pre-printed label including an optically detectable marker of known density, such as a stable colored line(s). A reader measures the density of this line with every scan and determines whether the density value falls within an acceptable range. This ensures that lines on drug panels are being accurately interpreted.
Conveniently, the QA portion of the invention is a label that may be disposed on the test device, adhesively or otherwise. For example, the label may be a pre-printed label formed of a suitable material that may be used in a conventional printing process and affixed to a test device. It will be understood that an optically detectable marker, such as a stable colored line(s) may be printed onto the label via any known printing method, such as digital printing, thermal printing and the like.
In any embodiment of the present invention, the label includes one or more optically detectable markers. For example, a single label may include up to 2, 3, 4, 5, 6, 7, 8, 9, 10 or more optically detectable markers.
As used herein, an “optically detectable marker of known density” is intended to generally refer to a colored feature that is optically detectable and which the optical density is known. As will be appreciated, the term “density” or “optical density” is used synonymously with absorbance, e.g., the ratio of the radiant flux absorbed by a body to that incident upon it, which may be measured over all wavelengths or at one or more specified wavelengths. An optically detectable marker for use with the present invention may be provided in any number of geometric shapes, but generally will be a circle, line, bar, square or ellipse. Additionally, an optically detectable marker may be disposed in or on any region of the QA label.
One of skill in the art would understand that the optically detectable marker may be formed from molecules containing chromophores which may be provided in any form or composition. For example chromophores may be present in any compositions of ink, pigment and the like which produces a consistent marker of known density. Further, the chromophores may be disposed on the QA label, e.g., by printing, stamping or the like, or may be disposed within and throughout the QA label. As such, one skilled in the art would appreciate that chromophores may be incorporated into the QA label when the label is formed.
Non-limiting examples of suitable test formats with which a test substrate having the QA features of the invention may be used are illustrated in
With reference to
The immunoassay device of the present invention may also include a barcode. As is generally known in the art, a barcode is an optical machine-readable representation of data. It will also be appreciated that the term barcode is intended to refer to both one dimensional and two dimensional barcodes.
As used herein, “assay data” is intended to refer to data pertaining to the features of the test device and assay(s) being performed on the test device. For example, such data includes the types of assays being performed on the device; analytes detectable using the device; location of physical features of the device, such as geometry of the device, location of QA labels, location of detection and control zones; type and location of SVTs; and device data, such as manufacturing information, age, size, type, and shape of device.
As used herein, “detection zone data” is intended to refer to data pertaining to the detection zones of the device (15). For example, such data includes number, size and location of detection zones; expected color and intensity of label accumulation; and type of label(s).
As used herein, “calibration data” is intended to refer to data pertaining to calibration of the scanning device and optimizing results of image recognition. For example, such data includes density values for positive and negative tests; parameters for increasing or decreasing detected density values; parameters for accepting or dismissing scans; and parameters for assessing light intensity.
As used herein, “QA label data” is intended to refer to data pertaining to the QA label on the test device. For example, such data includes number, shape, size and location of labels; number, shape, size and location of optically detectable markers; and known optical densities of markers.
As used herein, “optical data” is intended to refer to data pertaining to the optical recognition device. For example, such data includes optical recognition device data, such as type, size and recognition software; and scan data, such as wavelength(s) of electromagnetic energy used to perform a scan and scan settings.
As used herein, “subject data” is intended to refer to data pertaining to the subject from which the analyzed sample is taken. For example, such data includes subject information, such as name, medical history and prior testing data.
Instrumentation with which the QA label of the invention may be used are, as noted, image recognition devices, such as optical readers, scanners, imagers, cameras and other visually responsive analysis instruments. As is appreciated by one in the art, image recognition devices further include smartphones as well as other mobile technology.
A particularly preferred device for use with the invention is shown in
In various embodiments the system and functionality of the system allow for a variety of beneficial features. Such features include, but are not limited to automated analysis of test panels; automatic test menu recognition (e.g., barcode); in-process system quality control checks; image capture, data management/export functionality, and data archiving of results; and validation for use with multiple formats/test menus.
A number of benefits are achieved by the features of the system. Automation of the system eliminates result interpretation variability and subjectivity. Accuracy of the system is far superior than visual interpretation of test panels using the “naked” eye. Automation also allows increased throughput and scanning process speeds of approximately 15-30 sec. The flexibility of the system is also paramount and allows for multiple test formats.
In one embodiment, the system for use with the invention is the SureStep™ Instrument Test System with D×LINK™ Technology sold by GenPrime/Innovacon. Alternative commercially available instruments with which the invention may be adapted to use include, without limitation, those sold by Syntron, Mavand, Express Diagnostics, Ultimed, and MedTox.
In use, a method for confirming the validity of a visually readable analyte test result according to the invention is summarized as follows. An operator logs into the computer system. A collected donor sample is applied to a test device, which is then placed in the optical scanner. The software functionality (DxLINK™) is then activated by the operator and any information regarding the donor or test sample is inputted. Next the test device is scanned by activating the scanner. Results may then be viewed and any comments entered. The results may be printed and/or exported and archived in a data storage medium. The method is summarized in
In one exemplary embodiment, such as that depicted in
In other exemplary embodiments, such as those depicted in
In other exemplary embodiments, such as those depicted in
If the signal from the QA label (10) deviates within tolerance limits of the predefined value from the parameter stored in the two dimensional barcode (20), in one instance the test result may be automatically adjusted upward or downward according to the scanned value of the optically detectable marker (30) of the QA label (10); in another instance no change to the signal from the test line is necessary.
As such, the system of the present invention includes a processor having computer-executable instructions for performing such operations. For example, such operations include comparing the known density value with a test density value of at least one optically detectable marker generated via an optical image generator; determining whether the test density value is within a preset deviation of the known density value of an optically detectable marker (30) of the QA label (10); determining the density value of the detection zone (15) and when the test density value is within a preset deviation; increasing (or decreasing) the density value of the detection zone (15) when the density value of the optically detectable marker (30) is in agreement within error of the defined density value of the QA label (10).
In various embodiments, the preset deviation is two, three, four or more standard deviations from the known density value. For example, the preset deviation may be two, three, four or more standard deviations above or below the known density value of the optically detectable marker (30).
The following examples are intended to illustrate but not limit the invention.
The GenPrime Reader™ consists of an Avision AVA6™ flat bed scanner connected to a PC with GenPrime's software algorithm installed. The scanner captures an image of a Drugs-of-Abuse (DOA) test device and the algorithm quantitatively determines whether the presence or absence of a test line is associated with a positive or negative drug result. The Reader requires a consistent high quality image for accurate analysis and to ensure a consistent image capture, an in-process QA system needs to be established. This example describes the use of a QA label, which contains a stable colored line(s) of known density. The Reader measures the density of this line with every scan and determines whether the density value falls within an acceptable range. The analysis of the QA label simultaneously determines whether critical parameters of the Reader such as lamp intensity, scanner calibration, and software algorithms were performing within specifications. This ensures that lines on drug panels were being accurately interpreted. If a reading is outside the accepted range, a drug test result would be noted as invalid and corrective actions could be implemented.
In order to test the concept of an in-process QA system using labels attached to test devices, the consistency of labels manufactured by Typolac were evaluated. These labels are shown in
The goal of this study was to evaluate the consistency of the QA label manufactured by Typolac and define the specifications for the QA label. This example describes and discusses the results of these studies.
Evaluation #1: QA Label Variation on Card Surface
In order to determine the level of variation between QA labels, a series of 6.5 cm×10 cm white index cards were affixed with nine to ten QA labels (
Evaluation #2: QA Label Variation Inside of Key Cup™
In test formats such as the Key Cup™, the QA labels will be placed under the cup's plastic face. To evaluate the labels' performance under these conditions three DBT-187 Key Cups™ were disassembled and the QA label placed in its designated area under the plastic (see
Table 1 shows the results of multiple scans of individual labels placed on the index cards. The mean label density ranges between 19.7 and 28.0. The scanner CVs rarely exceed 3%, demonstrating the consistency of the software and scanner system. It was also noted in this study that there was no correlation of mean density to location of the label on the card or whether it was in a vertical or horizontal position. Table 2 displays the mean density for the 56 labels shown in Table 1, which is 23.6 with a standard deviation of 1.7. A value of 23.6 is approximately equivalent to a value somewhere between a G7 and a G8 score on the Abon Gold Color Card™ scanned on the surface of a test format. See Table 5 for a comparison of G score values and density measurements. The coefficient of variation for all labels is 7.2%, a measure of label to label variation plus Reader variation, which is expectedly higher than the variation for multiple scans of the same label. One could estimate that the label to label variation is approximately equivalent to the total variation from Table 2 minus the average Reader variation from Table 1 (7.2%-1.8%=5.4%). On the other hand, it could be argued that a better measure would be to subtract the maximum Reader variation from the combined variation, which would be 7.2%-5.8%=1.4%.
Table 3 displays the results of the analysis of individual Typolac labels placed under the plastic of a Key Cup™ as shown in
The purpose of this study was to evaluate the printing consistency of the Typolac QA label and generate quantitative data that would permit GenPrime to set specifications for the label. There were three major evaluations in this study. The first involved assessing the variation from multiple scans of a single label (n=12 scans). This provided data on the consistency of the Reader, which is a measure of both image capture and software algorithm variation. The second experiment evaluated the label to label variability from randomly selected labels. This tested the printing consistency of the labels plus the Reader variation and allowed determination of a QA specification for labels on the Multi-line card format. The third experiment determined the value and variability of labels placed under the plastic cover of a Key Cup™ test format. This tested how the plastic barrier affects the magnitude of both label density and variability.
It should be noted that three different variability measurements were generated in this study. The first shows the intra-label variation of 12 separate scans of a single label, which encompasses the combined variation of image capture and software analysis. These data are displayed in Table 1. The second, which is shown in Table 2, illustrates the total label to label variation of 56 individual labels, which takes into account both printing variation and Reader variation. The third, shown in Table 4 displays the label to label variation for labels placed under the plastic housing of a Key Cup™.
Thus, data are presented showing Reader variation and label to label variation. The latter includes results for both a multi line card device and under the plastic of a Key Cup™ device. These exemplify two types of formats in which QA labels may be applied.
It was found that the Reader variation was relatively small. The CV rarely exceeded 3%. The QA label brightness of labels on the index cards is estimated to equate to a density of somewhere between G7 and G8 and has a mean density of 23.6 with an overall coefficient of variation of 7.2% for all labels when placed on the surface of a card.
The mean density for labels under the Key Cup™ plastic housing was 14.7 with a coefficient of variation of 4.7%. This value more closely equates to a G8 score. Note in Table 5 that a G8 has a density of 26.6 on the surface of the card and a density of 13.2 under the plastic housing.
For labels placed on the card surface, the minimum and maximum values were 19.7 and 28.0 respectively. For labels in the Key Cup™, the minimum and maximum values were 11.9 and 15.8 respectively. These minimum and maximum values were to set acceptable ranges for the QA label at time of manufacture. Alternatively, the values may be set to an acceptable range to be within two standard deviations from the mean of these values. This specification would represent 95% of all theoretical values for an infinite sample size.
The range for a QA label on the surface of a Multi-line format test device may be set to between 20.2 and 26.8 density values. For labels under the plastic housing of Key Cup™, the range for a QA label on the surface of a Multi-line format should be set between 13.3 and 16.1 density values. Test formats with labels falling outside this range would be rejected as invalid.
It is contemplated that future versions of the QA label may contain at least two color strips, one of G6 and one of G4. This would serve not only to survey image quality but also image sensitivity. An exemplary QA label would have a density of at least one line in the range that would allow accurate interpretation of G4 values.
Although the invention has been described with reference to the above example, it will be understood that modifications and variations are encompassed within the spirit and scope of the invention. Accordingly, the invention is limited only by the following claims.
This application claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Ser. No. 61/413,310, filed Nov. 12, 2010, the entire contents of which are incorporated herein by reference in its entirety.
Number | Date | Country | |
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61413310 | Nov 2010 | US |