Anticoagulant Therapy in Patients with Atrial Fibrillation and Risk of Bleeding: Interim Analysis: Tyrion Study

Background/Introduction: New oral anticoagulants (NOA) showed a lower risk of bleeding in patients with atrial fibrillation as compared to traditional oral anticoagulants (TOA). However, some studies highlighted a higher frequency of gastrointestinal bleeding related toNOAthanTOA[1–3]. Objective/Aim: To assess the risk of bleeding events (i.e. overall, gastrointestinal and intracranial) in patients with NOA, as compared to TOA. Methods: The TYRION study had a case–control design with a historical cohort and included patients of four Italian regions with at least one NOA or TOA prescription from July 1st, 2012 to December 31st, 2015. Exposure and outcome data were extracted from the regional databases of drug reimbursement claims and the regional records of hospital discharge, respectively. The databases were linked by an anonymous unique patient identification number. Cohort entry was defined by the date of the first prescription of NOA or TOA after July 1st, 2013 among patients who were free from any anticoagulant prescription in the previous year. Cases were patients with at least one record of bleeding event. The date of the first bleeding was the index date. In the primary analysis, two controls were matched for each case by year of birth, year of cohort entry, sex and duration of follow-up. In the secondary analysis, cases were stratified into intracranial and gastrointestinal bleedings, and then they were matched with two controls. In each analysis, TOA users were the reference group. The odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by conditional logistic regression for the association of NOA use with bleeding events, adjusted for region. Results: This interim analysis included data provided by three regions (Tuscany, Lazio, Marche). The cohort included 33,314 patients. At the cohort entry, 17,263 and 16,051 patients received NOA and TOA, respectively. During the follow-up period, 537 patients switched from NOA to TOA, while 6098 from TOA to NOA. A total of 1557 cases of overall bleeding, 222 cases of intracranial bleeding and 403 cases of gastrointestinal bleeding were recorded. The adjusted ORs of NOA were: 0.54 (95% CI 0.47–0.61) for overall bleeding, 0.48 (95% CI 0.34–0.67) for intracranial bleeding, and 0.83 (95% CI 0.65–1.07) for gastrointestinal bleeding. Conclusion: These results showed a significant protective effect of NOA, as compared to TOA, for overall and intracranial bleedings only. The final analysis is expected to confirm the results