Point-of-Care Coagulation Testing: Stepping Gently Forward

Abstract

As a specialist in diagnostic coagulation, I am frequently faced with a patient who does not want to drive into Boston to be monitored for warfarin (coumadin) therapy at our anticoagulation clinic. This fact has not been lost on instrument manufacturers, who have produced multiple point-of-care devices for home monitoring of the prothrombin time/international normalized ratio (PT/INR). The number of individuals taking coumadin for atrial fibrillation, recurrent venous or arterial thrombosis, and other conditions is tremendous. The total number of prescriptions for warfarin in 1999 exceeded 20 million. The report by Ambrose et al. (1) in this issue of Clinical Chemistry investigates the performance of a point-of-care testing (POCT) analyzer for activated clotting time (ACT) measurement in a population of children undergoing extracorporeal membrane oxygenation. The performance of the POCT analyzer was equivalent to that of other commercially available POCT instruments for ACT measurement, but the results showed no relationship to the gold standard test of plasma heparin concentration. This study highlights several issues relevant to point-of-care coagulation assays. One of the most important is whether the tests are performed at a clinical site or at home. A recent survey of coagulation analyzers identified 17 devices (2). Of these, 15 had been cleared for use by the Food and Drug Administration as of October 1, 2000. Of these, 12 can be used to perform a PT/INR, 11 can perform an ACT or related test to manage heparin therapy, and 8 are available for partial thromboplastin time (PTT) measurements. Four of the instruments have had a patient self-testing program for home monitoring of PT/INR to optimize coumadin therapy. POCT for coagulation at a clinical site by certified health professionals has some unique aspects, as noted below, but the major practice change for point-of-care coagulation studies is home testing for coumadin dose …