Performance evaluation of a new small-volume coagulation monitor: the SmartCheck INR system

The SmartCheck INR (Unipath, Bedford, England) is a point-of-care device for professional and patient self-monitoring of oral anticoagulant therapy. It measures the international normalized ratio (INR) and assesses test strip integrity, temperature, and sample quality. No significant differences were found in SmartCheck INR results from 3 different instruments or in 3 test-strip lots. Within run imprecision was 0.89% and 6.36% for low and high control samples, respectively (mean INR, 0.99 and 4.08, respectively). Comparability was assessed in 68 patients receiving warfarin by using PTHS Plus (Instrumentation Laboratory, Lexington, MA) and Innovin (Dade Behring, Marburg, Germany) thromboplastins. Good correlations were observed between the methods (r = 0.89 and r = 0.90, respectively) with no significant differences in means: SmartCheck INR, 2.82; Innovin, 2.75; PTHS Plus, 2.74. Clinical agreement with laboratory methods was 88% for Innovin and 97% for PTHS Plus. The SmartCheck INR was easy to use with no mechanical failures during the evaluation and a low test-strip failure rate of 4.7%. The SmartCheck INR provides accurate and reproducible results and is suitable for routine monitoring of oral anticoagulant therapy in the majority of patients.