AN EVALUATION OF SEVERAL LABORATORY TESTS AND TEST COMBINATIONS IN THE DETECTION OF LUPUS ANTICOAGULANT

The laboratory assessment of the lupus anticoagulant, a factor frequently associated with venous and arterial thrombosis, recurrent miscarriages and abortions, is not straightforward, as indicated by the variety of tests proposed and the different results obtained. On account of the marked variability and heterogeneity of lupus anticoagulant among patients, no single test or reagent will identify all patients with lupus anticoagulant, and a panel of several tests has to be used. This is time consuming and increases the workload of the laboratory. The aim of this study was to assess the minimum number of tests necessary for the satisfactory identification of the patient with lupus anticoagulant. Our study confirms that lupus anticoagulant may be present in a significant number of patients with normal routine activated partial thromboplastin time, a test which therefore cannot be used as the sole criterion for identifying patients suspected of having lupus anticoagulant. In contrast all patients who had positive results in at least one test could be detected (100% sensitivity) with two combinations of tests: (1) dilute activated partial thromboplastin time and Kaolin clotting time and (2) dilute activated partial thromboplastin time and tissue thromboplastin inhibition test. Since the latter inhibition test has been reported to give a high number of false-positive or negative results, we suggest the combination of dilute activated partial thromboplastin time and Kaolin clotting time as the standard pair of tests for the screening of suspected lupus anticoagulant patients.