Clinical Impact of Point-of-Care vs Laboratory Measurement of Anticoagulation

Abstract

Patients using anticoagulation point-of-care (POC) monitors are advised to periodically test these systems against laboratory methods to monitor performance. The international normalized ratio (INR), however, can vary between test systems owing to different instrument-reagent combinations. In a randomized study evaluating warfarin self-management, we compared INR measured by patients on a POC monitor (ProTime, International Technidyne Corporation, Edison, NJ) with those obtained at a hospital laboratory within 1 hour Ninety-one paired INR determinations from 55 patients met inclusion criteria. Clinical agreement in which POC and laboratory INR were within or outside the target INR range occurred in 56 (62%) of 91 cases (kappa = 0.35). The mean (SD) difference between POC and laboratory INR was 0.44 (0.61). Six pairs differed by 1 or more INR units, 3 at study initiation resulting in POC monitor replacement. The accuracy of INR self-testing with ProTime was acceptable. The small failure rate of INR agreement might be clinically important, suggesting the need for external quality control systems.

Assessing Clinical Laboratory Quality: A College of American Pathologists Q-Probes Study of Prothrombin Time INR Structures, Processes, and Outcomes in 98 Laboratories

“…Karon and colleagues, 8 as well as others, 9,10 have demonstrated that marked differences in INR results occur between central laboratory and point-of-care instruments, and these biases among locations change over time, complicating physician interpretation of results. 8 Hence, it is likely that the INR for most testing performed outside the clinical laboratory was different from that of the clinical laboratory, requiring additional education of physicians using this type of testing in addition to the INR testing performed in the central laboratory.…”

Influenza Vaccination and Vitamin K Antagonist Treatment

“…Good correlation between capillary and venous determination of INRs has been previously found. 26,27 Notwithstanding, we measured capillary and venous INRs at time 0 and at time 28. Our results showed good correlation between the 2 methods.…”

Correlation of Point-of-Care International Normalized Ratio to Laboratory International Normalized Ratio in Hemodialysis Patients Taking Warfarin

“…icrofluidics technology for point-of-care (POC) International Normalized Ratio (INR) measurement is an established, reliable, and efficient means of monitoring patients requiring chronic warfarin therapy (1)(2)(3)(4)(5). Minimizing both the amount of blood sampled and the turnaround time for test results, POC testing has become the standard of care for chronic warfarin management strategies.…”

“…The three main objectives of this study were: (1) to determine the correlation between POC INR and standard plasma INR (Lab INR) values in hemodialysis patients receiving chronic warfarin therapy, (2) to determine the influence of anemia on the accuracy of POC INR test results in these patients, and (3) to compare practical sites for POC INR blood sampling to confirm which were feasible and which were inappropriate. For this purpose, finger-stick blood samples for POC INR were compared with the hemodialysis access sources [indwelling central venous catheter, arteriovenous (AV) fistula, or graft] to standard dialysis INR blood sampling.…”