Performance of a point-of-care device in determining prothrombin time in supra-therapeutic INRs

• Published in: International journal of laboratory hematology Vol. 35; no. 2; pp. 211 - 216
• Main Authors: Hashimoto, V. A. M., De Paula, E. V., Colella, M. P., Luz Fiusa, M. M., Montalvao, S. A. L., Machado, T. F. G. S., Orsi, F. A., Annichino-Bizzacchi, J. M.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-04-2013
• Subjects: Anticoagulants; Humans; International Normalized Ratio - instrumentation; International Normalized Ratio - standards; point-of-care; Point-of-Care Systems - standards; prothrombin time; Prothrombin Time - instrumentation; Prothrombin Time - standards; validation; warfarin
• ISSN: 1751-5521; 1751-553X
• DOI: 10.1111/ijlh.12026

Summary
Introduction
Point‐of‐care (POC) devices have been widely adopted for monitoring prothrombin time (PT) (INR) following the demonstration of their accuracy compared to standard INR determination. However, guidelines suggest confirmation of POC results when INRs increase above therapeutic range, due to concerns regarding possible inferior performance of POC devices in high INR levels. Unfortunately, patients with supra‐therapeutic INRs are underrepresented in studies that validated these devices.
Methods
We performed a prospective evaluation of the performance of a POC device in monitoring oral anticoagulation in patients with INR values above 3.5 in a University outpatient anticoagulation clinic. During a 6‐month period, 2322 INR determinations were performed with a POC device, and results above 3.5 were immediately repeated on an automated coagulometer.
Results
Dual INR determinations by two methods were obtained in 160 visits, with a mean INR from the POC device of 4.52 ± 0.96. Both classical statistics and clinical concordance analysis yielded satisfactory results when the two methods were compared.
Conclusion
Our results demonstrate that POC devices present good correlation with standard laboratory methods for PT determination in supra‐therapeutic INRs and that differences in clinical management do not support the need for systematic confirmation of these results in nonbleeding patients.