A Sensitive DRVVT Reagent System for the Detection of Lupus Anticoagulants

Abstract

Lupus anticoagulants are antibodies that inter fere with the phospholipid-dependent steps in in vitro blood clotting. The dilute viper venom (DVV)test is a phospholipid-limiting assay in which a plasma sample is preactivated with the venom from the pit viper Vipera russelli, which contains specific activators for factors X and V. A diluted sample of purified phospholipid and cal cium ions is added, and the clotting time is determined. If the DVVtest is prolonged, a DVVconfirm is then per formed. An excess of phospholipid is added to the test mixture of patient plasma and DVVtest sample. In most patients with lupus anticoagulants (LACs), addition of excess phospholipid will (partially) correct the prolonged DVVtest. We investigated a new formulation of the DV Vtest and DVV confirm that consisted of a more purified phospholipid reagent system. Twenty-six normal donors had negative results in both assays. A group of 42 patients were compared using the old and new formulations of the DVVtest and DVVconfirm. Thirty-six patients had agree ment of results between the old and new formulations. Of the six remaining samples, five that had been negative with the old formulation were positive with the new for mulation. Of these five, three of three had a positive an ticardiolipin antibody by enzyme-linked immunosorbent assay. The last patient was positive with the old formu lation and negative with the new, but this patient had a negative anticardiolipin antibody. Therefore, these re sults suggest that the new formulation of the DVVtest and DVV confirm is more sensitive to the presence of LACs.