Lupus anticoagulant testing
The present invention relates generally to the field of diagnostic screening and diagnostic assays. In particular, the present invention provides an improved, rapid, and efficient method of screening for antiphospholipid antibodies, such as lupus anticoagulants (LA). The invention also relates to a kit for screening plasma levels for antiphospholipid antibodies in subjects in need thereof, such as those at risk for or suffering from, inter alia, antiphospholipid syndrome (APS) and systemic lupus erythromatosus (SLE).
1. A kit for detecting antiphospholipid antibodies in a test plasma sample, comprising:
(a) at least one negative control plasma sample;
(b) at least one procoagulant test reagent suitable for activating the extrinsic coagulation pathway; and
(c) a high phospholipid confirmatory substrate, wherein the high phospholipid confirmatory substrate is synthetic and is suitable for use as a confirmatory substrate with the at least one negative control plasma sample in (a) and in a coagulation assay involving the at least one procoagulant test reagent of (b),
wherein the high phospholipid confirmatory substrate is at least 1 mg/ml phospholipid concentration and is used with at least two coagulation assays.
2. The kit of claim 1 , wherein at least one coagulation assay is a dilute Russell Viper Venom Time assay (dRVVT), a dilute prothrombin time assay (dPT), or an activated partial thromboplastin time assay (aPTT), and wherein each assay comprises a screening step and a confirmatory step, wherein the confirmatory step of each assay uses the high phospholipid substrate of (c).
3. The kit of claim 1 , wherein the antiphospholipid antibodies are selected from the group consisting of lupus anticoagulants, anti-β2-GP1 antibodies, anti-protein C antibodies, anti-protein S antibodies, anti-complement antibodies, anticardiolipin antibodies, anti-thrombin antibodies, anti-prothrombin antibodies, anti-thrombomodulin antibodies, anti-tPA antibodies, anti-Factor XII antibodies, anti-kininogen antibodies, anti-annexin V antibodies and combinations thereof.
4. The kit of claim 1 , wherein the test plasma sample is derived from a subject at risk for or suffering from an autoimmune disorder.
5. The kit of claim 4 , wherein the autoimmune disorder is selected from the group consisting of antiphospholipid syndrome (APS), connective tissue diseases, immune thrombocytopenia purpura, Hashimoto's thyroiditis, rheumatoid arthritis, and systemic lupus erythromatosus (SLE).
6. The kit of claim 1 , further comprising a positive control plasma sample.
7. The kit of claim 1 , wherein the at least one procoagulant test reagent is tissue factor.
8. The kit of claim 7 , wherein the at least one procoagulant test reagent contains a low level of phospholipids.
9. The kit of claim 1 , wherein the high phospholipid substrate comprises a component selected from the group consisting of phosphatidylserine (PS), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), cardiolipin, phosphatidic acid, dioleoyl phosphatidylethanolamine (DOPE), phospholipid coated beads, phospholipid suspensions, and combinations thereof.
10. The kit of claim 1 , further comprising a buffer containing calcium.