Objective: To assess the phospholipid specificity of lupus anticoagulants (LAC) in autoimmune and drug induced LAC positive patients, and to determine their relevance with the clinical feature thrombosis.
Methods: Thirty-five plasma samples with LAC were tested. Of these, 22 samples were from patients with autoimmune disease: 12 had systemic lupus erythematosus (SLE) and 10 primary antiphospholipid syndrome (APS). These were compared with 13 patients with drug induced LAC. Antiphospholipid (aPL) activity was tested by inhibition of LAC activity in a modified coagulation assay using the phospholipids: egg phosphatidylethanolamine (PE), 20% phosphatidylserine/80% phosphatidylcholine (PS/PC), and 15% PS/65%PC/20%PE mixture. Anticardiolipin antibodies (aCL) were measured in all samples by ELISA.
Results: In the autoimmune group, 95% were positive for reactivity to PE, 68% for PS/PC, 68% for PS/PC/PE, and 77% aCL. Of the drug induced group, 69% were positive for reactivity to PE, but only 23% for PS/PC, 46% PS/PC/PE, and 23% aCL positive. In the autoimmune patient group, 64% had thrombotic episodes, all of which had anti-PE activity, and 64% had associated anti-PS activity. No drug induced patient had episodes of thrombosis.
Conclusion: Autoimmune induced LAC may contain a broader range of phospholipid specificities than those from drug induced patients. These data thus identify another potential reason why patients with drug induced LAC appear to be at less risk of developing APS than those with autoimmune LAC.