Method Description

The dilute Russell's viper venom time (DRVVT) screening assay is performed on the Instrumentation Laboratory ACL TOP. Patient plasma is incubated for a specified time, then combined with a DRVVT screening reagent containing Russell's viper venom, phospholipids, heparin neutralizing agents, calcium, buffers and stabilizers to trigger the coagulation process. Subsequently, the time to clot formation is measured optically using a wavelength of 671 nm. The patient DRVVT screening clotting time is normalized by dividing the patient result by the mean DRVVT screening clotting time of normal pooled plasma to yield a ratio (DRVVT screen ratio).

Patient samples with a prolonged DRVVT (DRVVT screen ratio ≥1.20) are further studied by adding an equal volume of normal pooled plasma (platelet-depleted) and repeating the DRVVT test procedure, with mathematical normalization, to yield the DRVVT mix (1:1) ratio and the DRVVT test using DRVVT confirmatory reagent (enriched in phospholipid), and results are expressed as the quotient obtained from dividing the patient DRVVT screening clotting time by the patient DRVVT confirmatory clotting time (DRVVT confirm ratio).(Thiagarajan P, Pengo V, Shapiro SS. The use of the dilute Russell's viper venom time for the diagnosis of lupus anticoagulants. Blood. 1986;68(4):869-874; package inserts: CRYOcheck LA CHECK dRVVT Screening Reagent. Precision BioLogic; 05/2023CRYOcheck LA SURE dRVVT Confirmatory Reagent. Precision BioLogic; 05/2023)