The lupus anticoagulant: results from 2257 patients attending a high-risk pregnancy clinic.

Routine investigation for recurrent pregnancy loss includes measurement of antiphospholipid antibodies under the perception that the lupus anticoagulant (LAC) is prevalent in this population. Our tertiary clinic sees ~250 new patients with recurrent pregnancy loss annually, in addition to those with systemic lupus erythematosus and/or antiphospholipid syndrome. We measure LAC using a 4-assay panel that expands on the 2 assays recommended by the International Society on Thrombosis and Haemostatis (ISTH) guidelines. Of 2257 patients tested for LAC during a 6-year period, 62 (2.7%) repeatedly tested positive. Only 5 patients (0.2%) had both a history of early recurrent miscarriage and LAC positivity. Patients with LAC had a significantly more frequent history of thrombosis (35.5% vs 2.4%). LAC was absent in an overwhelming majority of women with exclusively early recurrent pregnancy loss but was associated with sporadic stillbirth. Among our panel of assays, none was predominant, and an increasing number of positive assays was associated with an increased history of morbidity. Therefore, our results do not support the ISTH contention that 2 assays are sufficient to identify and describe patients with LAC. We found that a confirmed, repeated LAC was very infrequent even in a high-risk setting.