Prothrombinase Induced Clotting Time (PICT) and Commercially Available Diluted Russell's Viper Venom Times For The Monitoring Of New Oral Anticoagulants

Abstract The new oral anticoagulants such as Rivaroxaban (Bayer Healthcare) (R) Apixaban (BMS/Pfizer) (A) and Dabigatran (Boehringer Ingleheim) (D) have been approved for Several indications in the US and Europe. Initially it was suggested that these agents did not require monitoring at the approved dosages for specific indications, however there have been reported bleeding complications with some of these agents that warrants the monitoring of these drugs to optimize therapy in some patient populations. A new clot-based assay, the prothrombinase induced clotting time (PICT) (Pentapharm, Basal, Switzerland) has been developed to monitor the anticoagulant effect of these new oral anticoagulants. In the assay, plasma is mixed with FXa, phospholipids, calcium and RVV-V from the venom of the Daboia russelli. The prothrombinase complex formed and the Xa and IIa generated is inhibited by the test agent. Two other forms of diluted Russell's Viper Venom time, namely DRVVT (screen), and DRVVT (confirm) are also available for the laboratory diagnosis of the lupus anticoagulant. The purpose of this study is to compare the PICT teste with the two versions of DRVVT test times for the monitoring of newer anticoagulants. Materials Citrated blood was drawn from 15 donors and spun at 800 rpm to obtain platelet rich plasma (PRP). The PRP was removed and spun at 3000 rpm to obtain platelet poor plasma (PPP). Both PRPand PPP were frozen at -80oC for 24 hours. Thawed PPP and PRP were supplemented with A, R and D in a concentration range of 0-2.5 ug/ml. The plasma samples were analyzed using 3 PT/INR reagents (Innoven, Dade-Behring, Germany; Recombiplastin, Instrumentation Laboratories, Bedford, MA; Neoplastin, Stago, Parsippany, NJ), two APTT reagents (Platelin, TCoag, Ireland; Actin FSL, Instrumentation Laboratories, Bedford, MA), Heptest, the one stage PICT and the two versions of DRVVT. All assays were performed on the ACL 300 Plus (Instrumentation Laboratories, Bedford, MA) with the exception of the PICT and DRVVTs which were run on the ST4 (STago, Parsippany, NJ). Results In the PPP system, the A, R and D showed assay differences in the clotting times which demonstrated good sensitivity to D and R compared to A. The PICT and the two versions of DRVVT showed much higher sensitivity and linearity. The relative sensitivity to DRVVTs were higher than PICT. In the PT/INR assay, all reagents were sensitive to D and the Innovin and recombiplastin were sensitive to R and showed a weaker response to A. Similar responses were observed in the APTT and Heptest assay. In the PICT and DRVVTs, all drugs showed a concentration dependent increase. D was strongest followed by R, and A showed the weakest effect. In the PRP supplemented system, all agents showed a weaker effect on the clotting times in all tests, however PICT and DRVVTs demonstrated a concentration dependent response for all agents. Conclusions These results demonstrated that neither the PT/INR, APTT nor heptest can be solely used to monitor the effects of all of the new oral anticoagulants. The one stage PICT is a simple, fast, automated or semi-automated test which can be performed on any mechanical or optical coagulation analyzer to monitor the anticoagulant effects of these agents. Similarly the two versions of DRVVT can also be performed on these instruments. The one stage PICT and DRVVT tests can also be used to monitor the effects of these agents in other matrices such as PRP. These studies warrant clinical validation of this test in patients treated with the newer oral anticoagulant drugs. Disclosures: No relevant conflicts of interest to declare.