Mixing Studies While on Pradaxa?

From Sara Sneeden, Lee Memorial. Our hematologists are ordering mixing studies on patients who have been on Pradaxa® at home. These patients arrive at the hospital with VMax prothrombin time (PT) and activated partial thromboplastin time (PTT, APTT) and some time later the mixing study is ordered on a subsequent draw. Is there anything to be learned from this study? Is there a better specimen with regard to the timing of this test?

Hi, Sara, and thank you for contacting Fritsma Factor. No, there is nothing to be learned from a mixing study while the patient is on dabigatran (Pradaxa), and of course, no physician would want to discontinue anticoagulant therapy simply to get an accurate mixing study result. If they were willing to discontinue, the half-life of Pradaxa is short, and they could probably get useful results after the patient is off the anticoagulant for at least three days. This is pure guesswork, but I wonder if your hematologists are attempting to identify the type of anticoagulant that is in use, or perhaps attempting to monitor its therapeutic effect. Also, if they are looking for a lupus anticoagulant, you may be able to help them with the anti-cardiolipin antibody and anti-β-2 glycoprotein 1. It is probably worth checking with them. Geo