Management Strategies Following Slightly Out of Range INRs: Watchful Waiting vs. Dose Changes

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Blood Adv


Patients' international normalized ratios (INRs) often fall slightly out of range. In these cases, the American College of Chest Physician (ACCP) guidelines suggest maintaining the current warfarin dose and retesting the INR within the following two weeks (watchful waiting). We sought to determine whether watchful waiting or dose changes for slightly out of range INRs is more effective in obtaining in-range INRs at follow-up. INRs and management strategies of warfarin-treated patients within the Michigan Anticoagulation Quality Improvement Initiative (MAQI²) registry were analyzed. Management strategies included watchful waiting or dose changes. INRs slightly out of range (target range 2.0-3.0) and their associated management were identified. Multilevel mixed-effects logistic regression was used to estimate the probability of the next INR being in range adjusted for clustering due to multiple out of range INRs per patient. A total of 45,351 slightly out of range INRs (ranging 1.50-1.99 and 3.01-3.49) from 8,288 patients were identified. The next INR was slightly less likely to be in range with watchful waiting than with a dose change (Predicted Probabilities 58.9% vs. 60.0%, P-value = 0.024). Although a significant statistical difference was detected in the probabilities of the next INR being back in range when managed by a dose change compared to watchful waiting following a slightly out of range INR, the magnitude of the difference was small and unlikely to represent clinical importance. Our study supports the current guideline recommendations for watchful waiting in cases of slightly out of range INRs values.

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ePub ahead of print