Evaluation of a new commercial dilute prothrombin time in the diagnosis of Lupus Anticoagulants

A new commercial dilute prothrombin time (dPT), the Acticlot® dPT™ (American Diagnostica Inc., Stamford, USA) was evaluated in the laboratory diagnosis of lupus anticoagulants (LAC). This integrated test system consisting of a screening and a confirmatory protocol was compared with a LAC panel including an aPTT and a dRVVT test system. This dPT was also compared with the dPT performed with Dade Innovin® (Dade Behring, Marburg, Germany) in a dilution of 1:200, 1:100 and 1:50. 201 samples were analysed with the Acticlot® dPT and the dPT Innovin®. Normalised results of dPT Innovin® in all three dilutions showed sensitivities around 60%, although dPT Innovin® 1/50 expressed in seconds had a sensitivity of 72%. Acticlot® dPT screen showed a sensitivity of 51%. 1% (2/201) of the patients with positive clinical criteria for APS were demonstrated only with dPT Innovin®. The integrated test system Acticlot® dPT ratio has 23.7% and 80.0%, sensitivity and specificity, respectively. The Acticlot® dPT screen method has an acceptable sensitivity and is comparable with the dPT Innovin® 1/200. Compared to the dPT Innovin® 1/200 this commercial dPT screening assay picks up another 0.5% positive patients, although without clinical significance. The Acticlot® dPT as integrated test system, has a too low sensitivity in comparison with the combination of aPTT and dRVVT based method. Performing dPT Innovin® 1/200 supplementary to the aPTT and dRVVT test system can pick up another 1% of LAC positive patients. © 2008 Elsevier Ltd. All rights reserved.