Quality of anticoagulation with vitamin K antagonists in Spain: A systematic review with meta-analysis of national registries

Background: Vitamin K antagonists (VKAs) depend on appropriate time in therapeutic range (TTR). We reviewed studies in Spain providing data on the quality of oral anticoagulation with VKA in atrial fibrillation (AF) patients, to present an overview of the quality of this therapy in our country. Methods: Systematic review and meta-analysis of national studies. We searched PubMed, Web of Science and Google Scholar databases for studies published in the last 10 years, until June 2024. We reported the mean pooled TTR and proportion of international normalized ratios (INRs) in range (PINRR), as well as the pooled prevalence of poor quality of VKA therapy. Results: Seven studies were included in the analysis, for an overall cohort of 6953 patients (mean age 73.6-83 years). The pooled analysis gave a mean TTR of 63.22% (95% confidence interval [CI] 46.55-79.89) and a mean PINRR of 60.53% (95% CI 44.40-76.65). Accordingly, the pooled prevalence of a TTR <65% was 50.01% (95% CI 45.36-54.65), and the pooled prevalence of a PINRR <60% was 46.90% (95% CI 41.56-52.31). Similar results were observed in a sensitivity analysis performed including only those studies fulfilling very similar inclusion/exclusion criteria (n=5). Conclusion: The mean TTR and PINRR of AF patients on VKAs in Spain were below the recommended standards. Nearly 50% of patients showed poor anticoagulation control, remaining exposed to low-quality therapy and complications related to AF.