1. Using a Simple Prescription Gap to Determine Warfarin Discontinuation Can Lead to Substantial Misclassification.
- Author
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Lin KJ, Schneeweiss S, Pawar A, Singer DE, Liu J, and Gagne JJ
- Subjects
- Aged, Anticoagulants therapeutic use, Clinical Coding methods, Clinical Coding organization & administration, Electronic Health Records statistics & numerical data, Female, Humans, International Normalized Ratio methods, Male, Medicare statistics & numerical data, Practice Patterns, Physicians', United States, Atrial Fibrillation blood, Atrial Fibrillation diagnosis, Atrial Fibrillation drug therapy, Venous Thromboembolism blood, Venous Thromboembolism diagnosis, Venous Thromboembolism drug therapy, Warfarin therapeutic use, Withholding Treatment statistics & numerical data
- Abstract
Background: Warfarin remains widely used and a key comparator in studies of other direct oral anticoagulants. As longer-than-needed warfarin prescriptions are often provided to allow for dosing adjustments according to international normalized ratios (INRs), the common practice of using a short allowable gap between dispensings to define warfarin discontinuation may lead to substantial misclassification of warfarin exposure. We aimed to quantify such misclassification and determine the optimal algorithm to define warfarin discontinuation., Methods: We linked Medicare claims data from 2007 to 2014 with a multicenter electronic health records system. The study cohort comprised patients ≥65 years with atrial fibrillation and venous thromboembolism initiating warfarin. We compared results when defining warfarin discontinuation by (1) different gaps (3, 7, 14, 30, and 60 days) between dispensings and (2) having a gap ≤60 days or bridging larger gaps if there was INR ordering at least every 42 days (60_INR). Discontinuation was considered misclassified if there was an INR ≥2 within 7 days after the discontinuation date., Results: Among 3,229 patients, a shorter gap resulted in a shorter mean follow-up time (82, 95, 117, 159, 196, and 259 days for gaps of 3, 7, 14, 30, 60, and 60_INR, respectively; p < 0.001). Incorporating INR (60_INR) can reduce misclassification of warfarin discontinuation from 68 to 4% ( p < 0.001). The on-treatment risk estimation of clinical endpoints varied significantly by discontinuation definitions., Conclusion: Using a short gap between warfarin dispensings to define discontinuation may lead to substantial misclassification, which can be improved by incorporating intervening INR codes., Competing Interests: D.E.S. reports research support from Bristol Myers Squibb, and he is on the consulting/advisory Boards of Boehringer Ingelheim, Bristol Myers Squibb, Johnson and Johnson, and Pfizer, all for unrelated work. J.J.G. reports receiving salary support from grants from Eli Lilly and Company and Novartis Pharmaceuticals Corporation to the Brigham and Women's Hospital and having been a consultant to Optum, Inc., all for unrelated work. S.S. is the Principal investigator of investigator-initiated grants to the Brigham and Women's Hospital from Bayer and Vertex unrelated to the topic of this study. He is a consultant to WHISCON and to Aetion, a software manufacturer of which he owns equity. His interests were declared, reviewed, and approved by the Brigham and Women's Hospital and Partners HealthCare System in accordance with their institutional compliance policies. All other authors report no conflict of interest., (Thieme. All rights reserved.)
- Published
- 2022
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