Claims
- 1. A composition for use as a reagent solution in the determination of a differential white blood cell count which comprises, in admixture, an aqueous solution of:
- (a) a surfactant;
- (b) formaldehyde in a concentration of from about 4.5% to about 6.6% weight/volume;
- (c) a sugar alcohol; and
- (d) a buffer to maintain the pH of said composition at between about 6.6 and 7.6.
- 2. The composition of claim 1 wherein said surfactant comprises an alkali metal salt of an alkyl sulfate containing from about 10 to about 16 carbon atoms.
- 3. The composition of claim 2 wherein said surfactant comprises an alkali metal dodecyl sulfate.
- 4. The composition of claim 3 wherein said surfactant is sodium dodecyl sulfate.
- 5. The composition of claim 2 wherein said surfactant is present in an amount of about 0.36 mm.
- 6. The composition of claim 1 wherein formaldehyde is present in an amount of from about 5.3% to about 5.9% weight/volume.
- 7. The composition of claim 1 wherein said sugar alcohol is selected from the group consisting of sorbitol and mannitol.
- 8. The composition of claim 7 wherein said sugar alcohol is sorbitol.
- 9. The composition of claim 7 wherein said sugar alcohol is present in an amount of from about 9.0% to about 13.5% weight/volume.
- 10. The composition of claim 9 wherein said sugar alcohol is present in an amount of from about 11.0% to about 12.0% weight/volume.
- 11. The composition of claim 1 which further comprises an alkali metal chloride salt.
- 12. The composition of claim 11 wherein said alkali metal chloride salt is selected from the group consisting of NaCl, KCl and LiCl.
- 13. The composition of claim 12 wherein said salt is NaCl.
- 14. The composition of claim 12 wherein said salt is present in an amount of from about 68 mM to about 103 mM.
- 15. The composition of claim 1 wherein the pH of said composition is from about 6.9 to about 7.3.
- 16. The composition of claim 1 wherein said buffer comprises a mixture of Na.sub.2 HPO.sub.4 and NaH.sub.2 PO.sub.4.
BACKGROUND OF THE INVENTION
This is a divisional of co-pending application Ser. No. 009,423, filed Feb. 2, 1987, now U.S. Pat. No. 4,801,549, which is a continuation of application Ser. No. 06/773,166, filed Sept. 6, 1985, now abandoned.
There are five classes of normal white blood cells or leukocytes: neutrophils, lymphocytes, monocytes, eosinophils and basophils. It is a known medical diagnostic procedure to examine a dried, stained smear of blood on a microscope slide to determine the relative proportions of these five normal types of white blood cells, as well as the concentration of any abnormal cells. Such procedure is referred to as a differential white blood cell count and is described in Miale, J. B., "Laboratory Medicine--Hematology", pp. 822-830, 1126, 1127 and 1130, C. V. Mosby Company, St. Louis, Missouri (1967).
Recently, automated processes and automated flow system apparatus therefor have been developed to ease the burden of differential white blood cell counting, such as described in U.S. Pat. Nos. 3,741,875 and 4,099,917. These use cytochemical procedures to specifically identify and label individual cell types.
The procedure for preparing a cell suspension for use in such systems comprises treating an uncoagulated blood sample with a surfactant for about 1.5 minutes to precondition the red blood cells for lysis; thereafter adding a fixative to the cells for about 1 minute while maintaining a neutral pH; and incubating the mixture at 58.degree. C. to 60.degree. C. for about 2 minutes to lyse the red blood cells and fix the white blood cells, as described in U.S. Pat. No. 4,099,917. It is imperative in such processes that all of the red blood cells be lysed because the red blood cells outnumber the white blood cells by about 700 to 1. Because of this, even if one percent of the red blood cells remain unlysed, the differential white blood cell count cannot be accurately arrived at.
A major drawback to the prior art methods is the relatively extended period of time each analysis requires, e.g., as much as five minutes just to prepare the cell suspension, thereby rendering such methods undesirable for emergency sample analysis or for other situations in which rapid results are desirable. Accordingly, there is need for a method for the determination of a differential white blood cell count which is relatively rapid as compared to the prior art procedures. Such a method would have to completely lyse the red blood cells in the sample without damaging the white blood cells, causing no extra-cellular precipitation or clumping of cells, since such precipitates or cell clumps could generate ambiguities in the cell detecting and recognizing phase of the process.
The present invention relates to a method for the rapid determination of a differential white blood cell count in a sample More particularly, the invention relates to a method which comprises:
US Referenced Citations (11)
Divisions (1)
|
Number |
Date |
Country |
| Parent |
9423 |
Feb 1987 |
|
Continuations (1)
|
Number |
Date |
Country |
| Parent |
773166 |
Sep 1985 |
|
Patent Grant
4978624
