Usefulness of a Diluted Prothrombin Time for Accurately Diagnosing Antiphospholipid Syndrome

Abstract

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), respectively. 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 ratio. 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 indicates 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.

Analytical dilemmas in lupus anticoagulant detection

“…Alongside aPTT, the other PL-dependent routine coagulation screening test is the prothrombin time (PT), so perhaps inevitably, diluting the thromboplastin reagent has been employed to screen for LA, in the tissue thromboplastin inhibition test or dPT [56][57][58]. The use of a lower thromboplastin dilution, or undiluted reagent, operates as the confirmatory test.…”

Direct Thrombin Inhibitors and Factor Xa Inhibitors Can Influence the Diluted Prothrombin Time Used as the Initial Screen for Lupus Anticoagulant

“…6 However, dPT is a widely performed, welldocumented, and sensitive screening test for LA when recombinant thromboplastin is used. [7][8][9][10] It has been reported that a considerable number of laboratories (50% of laboratories participating in the European Concerted Action on Thrombophilia Foundation) were using dPT beside the recommended tests for LA screening. 12,13 In previous studies, prolongation of the dPT was found to be associated with higher risk of thrombosis, 14 and receiver operating characteristic curve analysis indicated that the dPT ratio might be more useful for predicting thrombosis than diluted Russell viper venom time.…”

“…12,13 In previous studies, prolongation of the dPT was found to be associated with higher risk of thrombosis, 14 and receiver operating characteristic curve analysis indicated that the dPT ratio might be more useful for predicting thrombosis than diluted Russell viper venom time. 10 Generally, a prothrombin-based assay performed with diluted thromboplastin has high sensitivity and specificity for the presence of LA, caused by both anti-b2GPI and anti-prothrombin antibodies. 8,15,16 According to the United Kingdom National Quality Assessment Scheme proficiency testing program, all the hemostasis laboratories that used the dPT as part of LA screening reported correct interpretation for all of the external quality control samples.…”

“…6 Although diluted Russell viper venom time and activated partial thrombo-plastin time (aPTT) sensitized with silica and low phospholipid concentration are primarily recommended, diluted prothrombin time (dPT) using diluted Innovin reagent (human recombinant thromboplastin; Siemens, Marburg, Germany) also provides an inexpensive assay with high sensitivity and high negative predictive value. [7][8][9][10] However, LA detection might be problematic in patients treated with the most commonly used anticoagulants such as vitamin K antagonists and unfractionated and lowmolecular-weight heparins (LMWHs). Thus, current guidelines recommend to postpone the laboratory investigation of LA after the anticoagulant treatment is discontinued.…”