Patent EA-000673-B1 (EA)
Title: Factor v ratio blood test for susceptibility to thromboembolism
Inventor: ARKEL YALE S
IPC: C12Q1/56
Filed: 1996-11-29
Abstract: 1. A method for identifying a patient at risk of a thrombotic disorder due to a Factor V defect, comprising: (a) incubating a test plasma with a first reagent comprising a phospholipid composition and a contact activator; (b) adding a second reagent comprising activated protein C to a first aliquot of the test plasma and incubating the first aliquot and the second aliquot; and (c) measuring the Factor V activity of the plasma in the first aliquot and in the second aliquot in the presence of Factor V depleted plasma and thromboplastin. 2. A method of claim 1 further comprising the step of determining a ratio of the Factor V activity of the second aliquot to the Factor V activity of the first aliquot. 3. A method of claim 2 further comprising the step of determining whether the ratio is above or below a predetermined threshold value, wherein a ratio below the predetermined threshold value identifies a patient with a Factor V defect. 4. A method of claim 2 in which the phospholipid composition is a naturally derived phospholipid, a synthetic phospholipid, or a combination thereof. 5. A method of claim 4 in which the phospholipid compound consists of approximately equal amounts of phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine. 6. A method of claim 1 in which the phospholipid composition constitutes from 0,25 micrograms to 75 micrograms per 100 microliter portion of the first reagent. 7. A method of claim 1 in which the contact activator is at least one member selected from the group consisting of micronized silica, kaolin, celite, and ellagic acid. 8. A method of claim 1 in which, during the measuring step, the plasma constitutes from a 1:2 to a 1:20 dilution in the remaining constituents, including an inert diluent solution. 9. A method of claim 1 in which the step of measuring the Factor V activity of the first aliquot and the Factor V activity of the second aliquot comprises the steps of: (a) adding Factor V deficient plasma to the first aliquot and to the second aliquot; (b) adding a third reagent comprising thromboplastin and a compound containing Ca<2+> ions to the first aliquot and the second aliquot, to initiate clotting; and (c) measuring the clotting time of the first aliquot and the clotting time of the second aliquot. 10. A method of claim 9 in which the Factor V deficient plasma is present in an amount at least equal to the amount of test plasma in the first aliquot and in the second aliquot. 11. A method of claim 1 in which the step of measuring the Factor V activity of the first aliquot and the Factor V activity of the second aliquot comprises: (a) adding a quantity of Factor V deficient plasma to the first aliquot and to the second aliquot; (b) adding a chromogenic substrate sensitive to a serine protease generated by Factor V activity; (c) adding thromboplastin to initiate the chemical reactions of the extrinsic portion of the clotting cascade; and (d) measuring the color change of the first aliquot and the color change of the second aliquot produced by reaction of  the serine protease with the chromogenic substrate. 12. A method of claim 1 in which the predetermined threshold value of the ratio of Factor V activities is determined by testing plasma obtained from a control group of Factor V-normal individuals. 13. A kit comprising, in combination, a set of reagents standardized to determine whether a patient is at risk of a thrombotic disorder due to a Factor V defect, comprising: (a) a first reagent comprising a phospholipid composition and a contact activator; (b) a second reagent comprising activated protein C; (c) a third reagent comprising Factor V deficient plasma; and (d) a fourth reagent comprising thromboplastin with Ca<2+>. 14. A kit of claim 13 in which the activating composition comprises a phospholipid compound and a contact activator. 15. A kit of claim 14 in which the contact activator is at least one member of the group consisting of micronized silica, kaolin, celite, and ellagic acid. 16. A kit of claim 1 for determining whether a patient is at risk of a thrombotic disorder due to a Factor V defect, by a method comprising: (a) a first reagent comprising a phospholipid composition and a contact activator; (b) a second reagent comprising activated protein C; (c) a third reagent comprising Factor V depleted plasma; and (d) a fourth reagent comprising thromboplastin with Ca<2+>. 17. A kit of claim 1 for determining whether a patient is at risk of a thrombotic disorder due to a Factor V defect by a method comprising: (a) a first reagent comprising a phospholipid composition and a contact activator; (b) a second reagent comprising activated protein c; (c) a third reagent comprising Factor V depleted plasma; (d) a fourth reagent comprising thromboplastin in the absence of Ca<2+>; and (e) a fifth reagent comprising a chromogenic substrate sensitive to a serine protease generated by Factor V activity.