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Time in therapeutic range and incidence of warfarin complications in a 20-year retrospective cohort

Abstract:

Objective: To characterize the time in therapeutic range (TTR) and estimate the incidence rate of complications (PTIRc) in adults with warfarin protocol. Design: Retrospective cohort based on medical records of patients older than 18 years, between 1996 and 2016 and followed for at least three months. Site: Hematology unit of a Venezuelan specialized cardiovascular center. Participants: Electronic health record. Main measurements: TTR and PTIRc. The variables were sex, functional illiteracy, occupation, International Normalized Ratio (INR) and follow-up time, which were analyzed with TTR and PTIRc using binomial logistic and Poisson regression models, respectively. Results: 2,770 patients were followed up for a total of 1,201,380 days, 42.3% had a TTR < 65% and 3.5% had INR 2.5-3.5. 61.8% had complications. PTIRc was 6.84/100 person-months (95% CI: 6.56-7.15). TTR < 65% showed significant adjusted OR with functional illiteracy and INR 2.5-3.5, while for higher PTIRc a significant RR was found in the two factors mentioned, shorter follow-up time, TTR < 65% and in women. Conclusions: Despite new anticoagulant treatments, warfarin is useful. As follow-up time increased, control was better and the rate of occurrence of complications decreased; however, the conditions that showed lower TTR and higher rate of occurrence of complications require a thorough review of follow-up especially in patients with functional illiteracy.