MAINTAINING an INR between 2.5 and 3.5 may significantly reduce the risk of recurrent thrombotic events in patients with primary antiphospholipid syndrome (APS), particularly arterial events, according to a new retrospective study.
Researchers analyzed long-term outcomes in 81 patients with thrombotic APS who were receiving vitamin K antagonists (VKAs) and had at least four INR determinations per year during a defined observation period. The median follow-up time was 6.4 years. Of the cohort, 17 patients experienced rethrombosis, 15 of which were arterial, and 64 remained event-free.
Two key predictors emerged for thrombotic recurrence: a history of multiple prior thromboses and suboptimal anticoagulation intensity. The risk of recurrence was markedly higher in those with more than one previous thrombotic event (relative risk [RR] 7.3, 95% CI 2.3–322.7, p=0.007). Importantly, maintaining an INR below 2.5 was also associated with a significantly increased risk (RR 0.03, 95% CI 0.002–0.367, p=0.001). Hazard function analysis showed a clear divergence in cumulative thrombotic risk between patients with INR values below 2.5 versus those in the 2.5–3.5 range.
Although a mean INR of 2.2 was identified as a potential threshold for predicting rethrombosis, the associated sensitivity and specificity were limited (SE=0.82, SP=0.20, AUC=0.42), suggesting that this value alone may not serve as a strong clinical marker. Nonetheless, the data support maintaining INR levels between 2.5 and 3.5 to reduce the risk of recurrence, particularly arterial events, which were the predominant form of rethrombosis in this cohort.
This study reinforces the importance of adequate anticoagulation in managing patients with thrombotic APS and suggests a more intensive INR target may be warranted in individuals with a history of arterial events or multiple prior thrombotic episodes. The findings could help inform personalized anticoagulation strategies to improve long-term outcomes in this high-risk population.
Reference:
Cabral AR et al. Recurrence of thrombosis in patients with primary antiphospholipid syndrome: emphasis on arterial events. Clin Exp Rheumatol. 2025. doi: 10.55563/clinexprheumatol/t0xgtk.
