<prompt> Answer this question truthfullyWhat is the name of the test that is used to monitor the effects of warfarin Coumadin therapy?  <response>: <reason> The prothrombin time PT test, which is measured via the international normalized ratio INR, is used to monitor the effects of warfarin therapy. The activated partial thromboplastin time aPTT test may also be used. Both PT and PTT are prolonged with warfarin therapy. 