Methods for subtyping lupus anticoagulants

Abstract

Two simple procedures were tested for their potential to identify β2-glycoprotein 1 (β2GPl) or prothrombin cofactor dependence among lupus anticoagulants (LA). The first comprised mixing test plasma 1:4 with β2GP1-deficient plasma instead of with normal plasma. β2GPl deficiency decreased, but did not abolish most LA detectable in KCT, DRVVT and APTT clotting tests. Mixing 1:4 with bovine plasma was evaluated in a second test based on the KCT in the expectation that prothrombin-dependent LA would be preferentially shortened. Bovine plasma had a similar correcting effect on LA in all three tests considered here. Conversely, a prothrombin antibody was found to have similar prolonging effect on all three of these tests. LA patient plasmas displayed considerable heterogeneity when analysed using a combination of these two tests. The clinical significance of these tests remains uncertain. DRVVT and KCT tests do not appear to discriminate β2GP1-dependent from prothrombin-dependent LA.