Antiphospholipid antibodies in a heterogeneous group of patients: experience from a central laboratory

The aim of this study was to evaluate the prevalence and the performance of lupus anticoagulant (LA) tests in a heterogeneous group of patients and to investigate the sociodemographic characteristics, patterns of referral, clinical manifestations and outcomes among these patients. The medical charts of 725 patients referred to a central coagulation laboratory during a 12-month period for LA were reviewed. The data collected included demographic characteristics, the specialty of the referring physicians, the clinical indications for ordering the test, and the influence of the test results on the diagnosis and the treatment approach. Special attention was paid to identifying clinical manifestations known to be associated with antiphospholipid antibodies (APLA). A positive test was defined by abnormal results obtained by at least two techniques from the reagents used and confirmed by a platelet-neutralising procedure. Chi(2) and t-tests were used for independent samples. Fifty-six patients (7.7%) were found to have LA. Rheumatologists and gynaecologists emerged as the major contributors to this group. The presence of LA was significantly associated only with systemic lupus erythematosus and thrombocytopenia. The number of patients treated with antiaggregants or anticoagulants tripled following the test results. A positive dRVVT test strongly correlated with elevated anticardiolipin antibodies. We concluded that LA tests are ordered by a variety of physicians but yield better results when ordered by rheumatologists and gynaecologists. In this heterogeneous cohort, it was most useful in the investigation of thrombocytopenia and suggests a pathogenetic role in this condition. The dRVVT test correlates most closely with elevated anticardiolipin antibodies.