An Evaluation of Point-of-Care Instrument for Monitoring Anticoagulation Level in Adult Cardiac Patients

MH Tay, SL Tien, TSJ Chua, LL Sim, TH Koh
Correspondence: Dr M H Tay, dr_taymh@yahoo.com

ABSTRACT
Introduction Rapid point-of-care measurement of anticoagulation has become feasible with the advent of new portable devices and offers the potential for home monitoring. This study evaluates the accuracy and feasibility of such a point-of-care device, the ProTime analyser as compared with standard laboratory method (IL MCL2) for monitoring the International Normalised Ratio (INR) level in cardiac patients on oral anticoagulation therapy.
Materials and Methods Fifty patients were studied. The majority were male (86% versus 14%). Chinese accounted for 37(74%) whereas Malay and Indian, constituted 9(18%) and 4(8%) respectively. The mean age was 55 +/- 12 years. Prosthetic heart valve replacement (46%) and atrial fibrillation (38%) were among the main indications for anticoagulation. The mean dosage of warfarin was 3.0 +/- 1.5 mg (range 1.0 to 6.5 mg) and the INR results ranged from 0.83 to 4.69 (based on the hospital laboratory method). Fingerstick and venous blood samples were collected from every patient and subjected to analysis by ProTime and IL MCL2 analysers.
Results There was a good correlation of INRs between ProTime venous and IL MCL2 venous, ProTime fingerstick and IL MCL2 venous and ProTime venous and ProTime fingerstick samplings, with correlation coefficients (r) of 0.9248, 0.9403 and 0.9557, respectively. The Bland-Altman plot also showed a good correlation between the methods used without any systematic bias (limits of agreement ranged from -0.422 to +0.606 INR units on average).
Conclusion This rapid point-of-care device appears to have an acceptable level of accuracy for measuring INR values in the recommended target ranges in adult cardiac patients on oral anticoagulation therapy.

Keywords: Point-of-care INR test, ProTime Microcoagulation System
Singapore Med J 2002; 43(11): 557-562