A comparison between capillary and venous blood international normalized ratio determinations in a portable prothrombin time device

The CoaguChek(R) PT system is a portable point-of-care device for prothromb in time testing that can be used with capillary and venous whole blood. Thi s system had been calibrated by the manufacturer in terms of the internatio nal normalized ratio (INR) for monitoring oral anticoagulant therapy. The p urpose of the present study was to compare capillary blood with venous bloo d INRs from healthy volunteers and patients treated with oral anticoagulant s using the same CoaguChek(R) PT system. Two different CoaguChek(R) PT stri p formulations [international sensitivity index (ISI), 1.5 and 1.1] were us ed in separate test series. The differences between capillary and venous bl ood INRs were statistically significant (P < 0.001) but the magnitude of th e differences was small. The mean relative deviations of the INR were 5.8 a nd 2.8% for the strips with ISI 1.5 and 1.1, respectively. These deviations are clinically acceptable. It is concluded that capillary blood can be rep laced by venous blood for the calibration of the CoaguChek(R) PT system. Bl ood Coagul Fibrinolysis 11:559-562 (C) 2000 Lippincott Williams & Wilkins.