Accuracy of a portable International Normalization Ratio monitor in outpatients receiving long-term oral anticoagulant therapy: comparison with a laboratory reference standard using clinically relevant criteria for agreement.
The accuracy of a new, portable INR monitor (CoaguChek, Boehringer-Mannheim, Indianapolis, IN) was evaluated by comparing INR results from the portable monitor with results obtained by a laboratory-based method. Dual INR measurements (portable monitor, laboratory) were performed in 163 consecutive outpatients receiving warfarin. Agreement in dual INR measurements was defined based on clinically-relevant expanded and narrow criteria and statistical criteria. Agreement in dual INR measurements also was evaluated as a function of increasing INR. The proportion of dual INR measurements that satisfied the clinically-relevant expanded, and narrow agreement criteria was 90%, and 86%, respectively. Seventy-nine percent of all dual measurements were within 0.5 INR units. The accuracy of the portable monitor was greatest for INR values less than 3.0; above this INR level, the portable monitor underestimated laboratory INR values. The proportion of dual INR measurements within 0.5 INR units for laboratory INR ranges of <2.0, 2.0-3.0, 3.1-4.0, and >4.0 was 98%, 87%, 57%, and 21%, respectively. We conclude that the portable INR monitor achieved a clinically acceptable level of accuracy when compared to the traditional laboratory method and provides a suitable alternative method of monitoring the INR in patients receiving warfarin.
Department of Medicine, McMaster University, Hamilton, Ontario, Canada.
J D
JD
Douketis
A
A
Lane
J
J
Milne
J S
JS
Ginsberg
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D001780:Blood Coagulation Tests / Q000295:instrumentation* / Q000592:standards / Q000706:statistics & numerical data; D002318:Cardiovascular Diseases / Q000097:blood / Q000188:drug therapy; D005069:Evaluation Studies as Topic; D005260:Female; D006470:Hemorrhage / Q000517:prevention & control; D006801:Humans; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D013923:Thromboembolism / Q000517:prevention & control; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects
D000925:Anticoagulants; D014859:Warfarin