We assessed the predictive accuracy of the Warfarin Pharmacogenetics Consortium (IWPC) algorithm in a prospective cohort of 376 high-risk elderly patients (≥65 years) who required new treatment with warfarin for either medical (non valvular atrial fibrillation) or surgical conditions (heart valve replacement), had ≥1 comorbid conditions, and regularly used ≥2 other drugs. Follow-up visits were performed according to clinical practice and lasted for a maximum of 1 year. Two hundred and eighty-three (75%) patients achieved a stable maintenance dose. Warfarin maintenance doses were low on average (median 20.3 mg/week, interquartile range, 14.1–27.7 mg/week) and were substantially overestimated by the IWPC algorithm. Overall the percentage of patients whose predicted dose of warfarin was within 20% of the actual stable dose was equal to 37.5%, (95% CI 32.0–43.3%). IWPC algorithm explained only 31% of the actual warfarin dose variability. Modifications of the IWPC algorithm are needed in high-risk elderly people.
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The study was fully supported by the Italian Drug Agency (Agenzia Italiana per il Farmaco) study code FARM9JNT9Y. The sponsor had no role in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. VS has been supported by Programma VALERE, University of Campania “Luigi Vanvitelli”. The authors thank Flavia Lo Passo for assistance with data management.
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The authors declare that they have no conflict of interest.
The study was approved by the ethics committees of all participating centers. All participants gave written informed consent.
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Filippelli, A., Signoriello, S., Bancone, C. et al. Prospective validation of the International Warfarin Pharmacogenetics Consortium algorithm in high-risk elderly people (VIALE study). Pharmacogenomics J (2019) doi:10.1038/s41397-019-0129-6