Summary
The objective of this retrospective study was to evaluate the potential ability of
diluted Russell viper-venom time (dRVVT) to identify antiphospholipid syndrome (APS)
in a lupus anticoagulant (LA)-positive patient population, already selected by other
LA clotting tests. Our cohort of positive LA patients was first identified in our
outpatients population by the following sensitive LA-detecting tests: Rosner index,
diluted prothrombin time (dPT) and Rosove index. Then the 227 consecutive LA-positive
patients were tested for dRVVT with the same blood sample. Anticardiolipin (aCL) and
anti-β2-glycoprotein-I (β2GPI) autoantibodies assays were also performed. APS using
Sapporo clinical criteria revised at Sydney, was found in 116 of these 227 consecutive
LA-positive patients. Results of the different tests were analysed statistically.
Using univariate analysis, dRVVT, dPT, IgG aCL and IgG anti-β2GPI autoantibodies were
significantly associated with APS. The receiver operating-characteristics (ROC) curve
defined the best cut-off value for dRVVT ratio at 1.61 with a good specificity (78%)
and a lower sensitivity (53%). A multivariate analysis using a binary logistic procedure,
retained the dRVVT ratio (≥ 1.61) and IgG anti-β2GPI autoantibodies (> 15 USG) as
being associated with APS (p = 0.018; odds ratio [OR] 2.39; 95% confidence interval
[CI] 1.2–4.7, and p = 0.0001; OR 3.2; 95% CI 1.5–6.5, respectively). To conclude,
these results agree with the need for LA criteria favouring specificity over sensitivity.
The use of a threshold around 1.6 for dRVVT ratio should help discriminate APS from
non-APS patients.
Keywords
Antiphospholipid autoantibodies - diluted viper venom time