The activated seven lupus anticoagulant assay detects clinically significant antibodies

Lupus anticoagulants are a heterogeneous group of autoantibodies detected by their effects on phospholipid-dependent coagulation assays. Persistent lupus anticoagulants are associated with thrombotic disease, but not all are clinically significant. Antibody heterogeneity and reagent and test variability dictate that at least 2 tests, of different types, should be used to screen lupus anticoagulants. The objective of this study was to investigate whether the activated seven lupus anticoagulant assay detects clinically significant antibodies. Eighty-two patients with antiphospholipid syndrome (APS) and 32 with systemic lupus erythematosus + positive for activated seven lupus anticoagulant and who were without thrombosis, who were positive by activated seven lupus anticoagulant assay, were investigated for lupus anticoagulants by dilute Russell's viper venom time, dilute activated partial thromboplastin time, and Taipan snake venom time, and for anticardiolipin antibodies. Fifty-seven of the APS patients were positive for lupus anticoagulants in multiple assays, 25 in activated seven lupus anticoagulant alone. Fourteen of the latter group were previously positive in other antiphospholipid antibodies assays, and 11 had only been positive for lupus anticoagulants by activated seven lupus anticoagulant. Twenty-eight had elevated anticardiolipin antibodies, 6 of whom were from the group that was positive in activated seven lupus anticoagulant only. Eight of the systemic lupus erythematosus + lupus anticoagulants (without thrombosis) patients were positive for lupus anticoagulant by activated seven lupus anticoagulant alone and had only been positive in activated seven lupus anticoagulant previously, and none had elevated anticardiolipin antibodies. The remaining 24 patients were lupus-anticoagulant positive in multiple assays, and 9 had elevated anticardiolipin antibodies. Dilute Russell's viper venom time and Dilute activated partial thromboplastin time are widely used to detect lupus anticoagulants and are considered to detect clinically significant antibodies. Activated seven lupus anticoagulant detected antibodies in APS patients who were positive by these assays and also lupus anticoagulants undetectable by the dilute Russell's viper venom time/dilute activated partial thromboplastin time reagents used, demonstrating its utility as a first-line or second-line assay.</p

Hyperhomocysteinemia and B-vitamin status after discontinuation of oral anticoagulation therapy in patients with a history of venous thromboembolism

Although hyperhomocysteinemia is an established risk factor for venous thromboembolism there is no consensus for routine determination of circulating homocysteine in the UK, either at the beginning or end of oral anticoagulation therapy. The purpose of this study was to evaluate the prevalence of hyperhomocysteinemia and its relationship to folate and vitamin B12 status in subjects with venous thromboembolism 4 weeks after discontinuation of warfarin therapy. In 78 consecutively recruited patients, plasma homocysteine was significantly higher (p &lt; 0.001) and red cell folate significantly lower (p = 0.03) than in controls. Plasma vitamin B12 was similar in both groups. Strikingly, 38.5% of patients had hyperhomocysteinemia (&gt; 15 micromol/l). Retrospective analysis revealed a significant positive association between plasma total homocysteine and duration of warfarin therapy (p &lt; 0.001) but a negative, though non-significant (p = 0.06), trend with warfarin dose. The results do not suggest any direct interaction between warfarin and plasma homocysteine but raise the possibility of reduced intake of a common food source of folate and vitamin K. One possibility is the shortage of green-leafy vegetables since patients are often advised to limit their intake of this major source of vitamin K. On the basis of this study we suggest that homocysteine screening should be carried out at the time that patients begin warfarin therapy.</p