Usefulness of a Diluted Prothrombin Time for Accurately Diagnosing Antiphospholipid Syndrome

The usefulness of lupus anticoagulant (LA) and several antibodies for predicting thrombosis was assessed in patients with idiopathic thrombocytopenic purpura (ITP), systemic lupus erythematosus (SLE), lupus like disease (LLD), recurrent abortion and primary antiphospholipid syndrome (APS). LA was measured using the diluted Russell Viper Venom test (DRVVT) and the diluted prothrombin time (dPT). In healthy volunteers, the median (range) of the DRVVT and dPT ratio were 0.97 (0.88 - 1.08) and 1.05 (0.85 - 1.29), re- spectively. The positive percent of dPT ratio was high in patients with ITP, SLE, recurrent abortion and primary APS. The sensitivity for thrombosis was highest for the dPT ratio and the specificity for thrombosis was highest for the DRVVT ra- tio. The sensitivity and the Odd's ratio for both the dPT and DRVVT ratio were high. A positive predictive value in DRVVT and a negative predictive value in dPT were high. The receiver operating characteristic (ROC) curve analysis in- dicates that the dPT ratio might be more useful for predicting thrombosis than the DRVVT ratio. The DRVVT and dPT ratios are useful for both the diagnosis of APS as well as predicting thrombosis.