The role of lipids in the detection of lupus anticoagulant by the dilute Russell Viper venom test: are platelets or reagents containing hexagonal HII phases necessary?

Liposomes prepared from rabbit brain extracts (RBE) and individual pure lipids (high phosphatidyl serine content, HIPS) were compared with frozen-thawed platelets (PLTS) in the dilute Russell Viper venom time (dRVVt). While all three preparations demonstrated sensitivity to lupus anticoagulant (LA) the highest detection rate was seen with RBE. For confirmation of LA, high concentration RBE achieved the most efficient correction of the defect. Electron microscopy and particle sizing showed RBE to be small, discrete liposomes, whereas HIPS and PLTS were aggregates of larger diameter particles. Low-angle X-ray diffraction showed no evidence of hexagonal HII phase. There appears to be no specific requirement either for platelets or for reagents containing hexagonal HII phases in the dRVVt. The dRVVt can be optimized by incorporating a simple dilute rabbit brain lipid mixture for detection of LA and a concentrated mixture as a correcting reagent.