Journal of Research in Medical Sciences (Dec 2000)
STANDARDIZATION OF PROTHROMBIN TIME TEST AND EVALUATION OF QUALITY OF PATIENT MANAGEMENT WITH WARFARIN
Abstract
Background. The most common mode of monitoring anticoagulation therapy is the use of prothrombin time (PT). There exist several methods for reporting results of PT. These include prothrombin time in seconds, prothrombin activity percent, prothrombin time ratio, prothrombin index and international normalized ratio (INR). Different sensitivities of thromboplastins along with various methods of performing the PT test and also different ways of reporting the results of tests have led into discrepancies in lab values among different laboratories which in turn has made appropriate pharmacotherapy with anticoagulation drugs quite difficult. In this study, we have compared different methods of reporting PT results and in vestigated the quality of patient management with warfarin. Methods. In this study twenty three blood samples of normal individuals and thirty nine patients under warfarin therapy were collected and PT (INR) was measured. Also, PT kits by Biomerieux/France and the PT kit prepared by our team were compared during these measurements. The method of measuring PT was Manual tilt tube technique. Comparison of different modes of reporting PT was done by linear regression analysis. Results. Comparison of the obtained regression lines on PT, PAP, PTR and INR by using the two kits show that INR is independent of the sensitivity of thromboplastin. By considering the recommended therapeutic range of INR, we found that only thirty one percent with Boimerieux kit and twenty eight percent with the prepared PT kit were in the therapeutic range. Eleven percent of patients were sub therapeutic shown by the two kits and fifty eight percent and sixty one percent were above therapeutic range using the Biomerieux kit and the prepared kit, respectively. Discussion. Standardization of PT can be done most accurately through reporting PT by INR. The noticeable percentage of patients out of therapeutic range confirmed by both kits shows the inappropriate management of patients receiving warfarin.
