Accuracy, reproducibility and clinical utility of the CoaguChek S portable international normalized ratio monitor in an outpatient anticoagulation clinic

Abstract

The accuracy and reproducibility of the CoaguChek S, and its clinical agreement with conventional laboratory international normalized ratio (INR) determination, were evaluated in an outpatient anticoagulation clinic setting. Forty-three patients provided 248 paired INR measurements for analysis. The paired results were highly correlated (r = 0.90). The mean coefficient of variation for the CoaguChek S for a random sample of 21 patients with three repeated tests each, was 4%. Clinical applicability was also measured by discrepant INR values, as defined in the literature by expanded and narrow agreement, and by INR values resulting in a different clinical decision by a blinded haematology registrar. Expanded agreement and narrow agreement between the two INR values occurred 90 and 88% of the time, respectively. The stricter criteria set down by the clinician resulted in 73% of paired results producing the same dosage decision. The CoaguChek S displayed good correlation with laboratory determination of INR and compared relatively well with expanded and narrow clinical agreement criteria.

The impact of non‐vitamin K antagonist oral anticoagulants (NOACs) on anticoagulation therapy in rural Australia

“…These are comparable with agreements found in other studies. 15,[17][18][19] For the analysis of proportion of dual readings within 0.5 units, the results were again similar to those found in other studies, although for the higher INR range, the proportion of dual results >4.0 in remote areas the agreement was only 50% of the time compared to urban (68%) and rural (82%) patients. This was a lower percentage of agreement than found by Jackson et al (57%) for practices based in rural Australia 17 .…”

“…In two Australian studies using CoaguChek S, the same device used in the Trial, agreement was found to be 90% against expanded criteria and 88% against narrow criteria in an outpatient clinic, and 93% against expanded criteria and 90% against narrow criteria in rural practice. 15,17 The Trial found 86% of dual measurements were within 0.5 INR units, which is similar to that found by Jackson et al 15 (83%), Jackson et al 17 (88%) and Douketis et al 19 (79%). The Trial's results on the percentage of dual measurements within 0.5 units achieved similar results for the lower result ranges, but the Trial achieved much higher measurements of agreement in the higher INR ranges than other studies.…”

“…The Trial's results on the percentage of dual measurements within 0.5 units achieved similar results for the lower result ranges, but the Trial achieved much higher measurements of agreement in the higher INR ranges than other studies. 15,17,19 From a clinical perspective, the margin of error for the PoCT device is most important in the INR range of 1.5 to 3.5 because decision about warfarin dosing will be influenced by relatively small differences in the INR between a PoCT device and a laboratory method. Based on the results obtained from the clinically relevant agreement analysis, the PoCT device provided acceptable levels of accuracy when compared with laboratory results for INR.…”

“…Based on the results obtained from the clinically relevant agreement analysis, the PoCT device provided acceptable levels of accuracy when compared with laboratory results for INR. However, the increased level of inaccuracy of the device at INR values above 3.5 or 4.0 may require the need for guidelines in the use of the device at these levels, as suggested by Jackson et al 15 The review by clinicians indicated that, as with INR, the wide limits of agreement for the other tests were not considered clinically significant.…”

“…For all the satisfaction questionnaires, questions were either designed specifically for the Trial or were taken from other studies. 15,22,23,45,47,48 1.9.…”