Accuracy of a portable prothrombin time monitor (Coagucheck) in patients on chronic oral anticoagulant therapy: A prospective multicenter study

A portable prothrombin time (PT) monitor allows patients on oral anticoagul ant therapy (OAT) to measure their PT at home. The purpose of the study was to evaluate the accuracy and precision of a portable PT monitor (Coaguchec k, Roche Diagnostics, Mannheim, Germany) as compared with laboratory method s. The prospective study was conducted in four centers of the Italian Feder ation of Anticoagulation Clinics. A one-month instruction phase was followe d by a six-month surveillance phase. Seventy-eight subjects on stable OAT ( 48 men, 30 women, age range: 18-75) were selected on a volunteer basis. Dua l measurements of INR values were performed in each subject both from finge r capillary blood by the monitor and from venous blood by the Anticoagulati on Clinic laboratory in three instruction sessions. The mean difference (bi as) of the monitor INR results when compared with the average of laboratory INR and monitor INR results was -0.025 (limits of agreement -LA: -0.84/+0. 81 INR units). The mean bias was -0.0675 (LA: -0.37/+0.23), +0.018 (LA: -0. 39/+0.35), and +0.039 (LA: -0.49/+0.55), respectively, for INR values lower than 2.0, between 2.0 and 3.0, and greater than 3.0. The overall precision coefficient of monitor INR was 0.370, while it was 0.23, 0.46, 0.29, and 0 .21, respectively, in Centers 1, 2, 3, and 4. The overall variation coeffic ient was 6.5% while it was 3.7%, 8.5%, 4.7%, and 4.9%, respectively, in Cen ters 1, 2, 3, and 4. Coagucheck has an acceptable level of accuracy for INR values in the range between 2.0 and 3.0. A wide variation in monitor perfo rmance was found among centers. (C) 2000 Elsevier Science Ltd. All rights r eserved.