Lupus anticoagulants (LA) are antibodies that interfere with and prolong in vitro phospholipid dependant clotting tests. Paradoxically, these autoantibodies are associated in vivo with clinical complications such as thrombosis and pregnany loss. Therefore, reliable identification of LA is of diagnostic importance.
One of the most commonly used and sensetive assays to detect LA is the dilute russell viper venom test (dRVVT). Despite the good diagnostic ability, there are muliple sources of variation in the dRVVT system that decreases its sensitivity and specificity for LA detection. There remains a significant problem with reagent variation in both the venom source and batch and the phospholipid concentration and source.
The objective of the present study was to evaluate the effect of phospholipid source on the sensitivity of dRVVT. It compared the LA detection rates of the dRVVT using four different sources of phospholipid: soybean lipid extract (SBE), rabbit brain extract (RBE), pig brain extract (PBE) and a synthetic phospholipid (Syn). Initially each phospholipid type was tested using 50-2500 mg/L of phospholipid with both a normal and lupus positive plasma to determine the concentration at which optimal discrimination was obtained. The concentration of RVV was also tested at 1, 2 and 4ug/L. 20 plasma samples from apparently healthy individuals were assayed at optimal concentration and the cutoff value between normal and LA plasmas was determined. Twenty lupus anticoagulant positive plasmas were then tested at low and high phospholipid concentatio to compare the sensitivity of each phospholipid to the lupus anticoagulant.