REGULAR ARTICLEAccuracy 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
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Patients
Consecutive ambulatory patients who were receiving long-term warfarin, for at least 3 months, and who were followed by the Anticoagulant Clinics of St. Joseph’s Hospital in Hamilton, Ontario, and the Reseau Sante de Richelieu-Yamaska in St. Hyacinthe, Quebec between January and October 1996 were eligible for this study. All patients participating in this study provided informed consent.
Study Protocol
All patients underwent blood testing during the same clinic visit to determine the INR using two methods.
Patients
Dual INR measurements using the portable monitor and laboratory methods were determined in 163 patients who were receiving long-term warfarin. The clinical characteristics of the patients is summarized in Table 1. In 132 patients with chronic atrial fibrillation or venous thromboembolism, the targeted INR was 2.0–3.0; in 10 patients with a tilting mechanical heart valve, the targeted INR was 2.5–3.5; in 21 patients with a ball-cage mitral mechanical heart valve or a history of systemic
Discussion
In this study, we investigated the accuracy of a new, rapid-response, portable INR monitor as compared with the conventional laboratory method to measure the INR in patients receiving long-term warfarin. Unlike other studies evaluating the accuracy of portable INR monitors, we attempted to use clinically relevant criteria to evaluate agreement between portable monitor and laboratory INR measurements. Based on our analysis, we conclude that the CoaguChek monitor achieved a clinically acceptable
Acknowledgements
We are indebted to Ms. Mimi Orescanin for her valuable technical and administrative assistance. Dr. Ginsberg is a recipient of a Career Investigator Award from the Heart and Stroke Foundation of Ontario. Dr. Lane is the Director of Scientific Affairs, Boehringer-Mannheim, Canada.
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2016, Thrombosis ResearchCitation Excerpt :Finally, another important issue is the consequence of the clinical discordance. POC-INR systems generally tend to overestimate the INR for values in the high range [9, 29] and underestimate INRs within or below the therapeutic target [11, 30]. In our study the Qlab tended to underestimate INR even in the therapeutic range where a significant difference was detected between both systems.
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