Accuracy of International Normalized Ratio Determined by Portable Venous-Blood Coagulation Monitor versus a Central Laboratory
CHIRASAK SIRITHUNY ANONT, MD*, KIERTIJAI BHURIPANYO, MD*, CHARUWAN KANGKAGATE, BSc**, WIRANEE WINYARAT,BNS*, PANARA T SRICHA YA , BNS*, KANOKKWAN WANGTIP,BNS*
Affiliation : * Bangkok Heart Institute, Bangkok Hospital, Bangkok 10320, **Her Majesty Cardiac Center, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
Materials and Methods : Paired venous blood INRs were performed in 220 consecutive out = = patient tests mainly in anticoagulated (n 210) and non-anticoagulated (n 10) individuals. Accuracy was evaluated in 220 tests by parallel assessment of INRs (CoaquChek and laboratory). Accuracy was determined using statistic regression analysis and clinical agreement (expanded and narrow criteria). Agreement in dual INR measurement also was evaluated as a function of increasing INR. =
Results : The CoaguChek significantly correlated with the laboratory measurement (r 0.89). The proportion of dual INR measurements that satisfied the clinical relevant expanderl, and narrow agreement criteria was 90 per cent and 86 per cent respectively. Eighty-two per cent of all dual mea surements 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 overestimated laboratory INR values.
Conclusions :The CoaguChek is an accurate alternative to laboratory assessment of INR at values< 3.0. The authors suggest the use of the monitor in non anticoagulated patients or anticoagu lated patients at values less than 3, as most physicians in Thailand prefer lower INR than in Western countries.
Keywords : Accuracy, Clinical Agreement, Portable INR, Laboratory INR, Warfarin
