Confirming Point-of-Care INR Test Results —Reply

In Reply We agree with Dr Fantz and the FDA guidance that confirmation venipuncture INR testing should be performed, at minimum, for all patients with POC INR testing results of 4.5 or greater. However, we recommend that each institution examine whether a lower threshold for performing POC INR testing (such as>3.5) would better meet patient safety goals. Donaldson et al conducted a single-institution study comparing POC INR values using 2 different POC devices (CoaguChek XS Plus and i-STAT) vs venipuncture INR (Stago). Based on prior studies, the authors defined a clinically significant INR difference (one that would result in differing dosing plans) as when the INR measurement was within therapeutic range on one device and out of therapeutic range on the other device or when both device INR measurements were out of range with an INR difference of 0.5 or greater. They also assessed the percentage of times that the device INR values differed by 0.4 INR units or more. The CoaguChek POC INR values were significantly different, with at least a 0.4-unit difference, from the venipuncture INR values in 33% of cases and the i-STAT POC INR values were significantly different, with at least a 0.4-unit difference, than the venipuncture INR values in 54% of cases.
Source: JAMA - Category: General Medicine Source Type: research
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