Evaluating quality of anticoagulation management among antiphospholipid syndrome patients: An observational cohort study

Context: Vitamin K antagonists (VKA) remain the mainstay of therapy for most nonpregnant patients with thrombotic antiphospholipid syndrome (APS) considering the increased risk of thrombotic events demonstrated in prospective direct oral anticoagulants trials. Little is known, however, about the quality of anticoagulation control among VKA-treated APS patients. Aims: This study aimed to evaluate the quality of anticoagulation control in a cohort of warfarin-treated APS patients in comparison with a control group of non-APS patients. Potential predictors of anticoagulation control were also explored. Subjects and Methods: The quality of anticoagulation control (monitoring and clinical outcomes) was retrospectively evaluated in a group of APS patients and compared to a control of non-APS patients. Results: Compared to non-APS, patients with APS had a significantly lower time in therapeutic range (TTR) (64.6 ± 27.8 vs. 77.3 ± 17.8, 95% confidence interval 5.6–19.8, P ≤ 0.001). A significantly higher proportion of patients in the APS group experienced poor anticoagulation control (TTR <70%) than non-APS patients (52.2% vs. 31.9%, Odds ratio 2.3 [1.4–4.1], P ≤ 0.001). APS patients were more likely to experience extreme supratherapeutic International Normalized Ratio (>4.5) than their counterparts (10.9% vs. 6.1%, P < 0.001). No difference in clinical events was reported. Gender was the only significant predictor of TTR among APS patients, as females experienced significantly lower TTR (Beta coefficient − 13.5, P = 0.05). Conclusions: Compared to general warfarin-treated patients with venous thromboembolism, APS patients were less likely to maintain therapeutic targets. Future studies that incorporate genetic, clinical, and social factors are recommended to fully understand the predictors of anticoagulation quality in this high-risk population.