Lupus Anticoagulants: Detection, Standardization, and Heterogeneity

Publisher Summary This chapter focuses on lupus anticoagulants (LAs), which are immunoglobulins (usually IgG, IgM, or a mixture of both) that interfere with in vitro phospholipid-dependent coagulation tests, such as prothrombin times (PT), activated partial thromboplastin time (APTT), Russell viper venom time (RVVT), and Textarin time. They may be encountered in various clinical settings including autoimmune diseases and non-autoimmune conditions, malignancies, certain medications, and infectious diseases. They are detected serendipitously as a result of routine coagulation testing, and their prevalence in various clinical conditions is widely variable. The high degree of variation seen between laboratories may be due to the choice of test systems. The wide disparity of LA detection may reflect a variety of variables including patient selection, test sensitivities, and response to treatment. The identification of LA in patients is important since its presence indicates a greater risk of thromboembolic complications. In addition to the association of LA/anticardiolipin (aCL) antibodies with venous/arterial thromboembolic events, other clinical complications include recurrent spontaneous abortion, transverse myelopathy, and nonbacterial thrombotic endocarditis. Drug-induced LA has been associated with a various medications including hydralazine, chlorpromazine, quinidine, and procainamide. The heterogeneity of LAs explains the multiple laboratory assay systems necessary to detect these inhibitors.