The laboratory heterogeneity of lupus anticoagulants.

Approximately 2% of the patients screened in our laboratories with activated partial thromboplastin times are found to have a lupus anticoagulant. Recognition of lupus anticoagulants has assumed new importance because of a number of associated clinical conditions. Recurrent spontaneous abortions, arterial and venous thrombotic disease, and polyneuropathy have been described in patients with lupus anticoagulants. Although the clinical heterogeneity of these patients has been recognized increasingly, the laboratory identification of the lupus anticoagulant is still confusing and frustrating. In many cases, the diagnosis of this inhibitor is one of exclusion following a series of ambiguous mixing studies and variable factor assays. We studied ten patients with atypical laboratory results. Of particular significance are patients with a time-dependent enhancement of the lupus anticoagulant effect and patients with lupus anticoagulants that manifest a preferential inhibition of the prothrombin time rather than the activated partial thromboplastin time. We also confirmed the sensitivity of the platelet neutralization procedure in the identification of the lupus anticoagulant.