Delayed diagnosis contributes to increased thrombotic burden and independently predicts severe organ damage in thrombotic antiphospholipid syndrome

Objectives To investigate the impact of time to diagnosis on damage accrual in thrombotic antiphospholipid syndrome (APS). Methods Retrospective cohort study including 252 patients with thrombotic APS (Sydney criteria). Time to diagnosis was defined as the period from the first thrombosis to diagnosis (diagnostic delay ≥12 months). Recurrent events occurred during antithrombotic therapy. Damage was assessed using the damage index for APS (DIAPS). Risk factors for diagnosis and treatment delay (≥12 months) were assessed. Cox regression analysis was used to determine predictors of damage (DIAPS ≥1) and severe damage (DIAPS ≥ 3). Significance was set as α < 0.05. Results Most patients were female (76.7%) with primary APS (71.8%) and a median age at onset of 40.5 (28–51) years. The median time to diagnosis was 12 months (≥12 months, 53.6%). Damage and severe damage affected 75.4% and 21.0% of patients, respectively. Diagnosis delay was associated with higher cumulative thrombotic events, recurrent thrombosis and anticoagulation delay (all p < .001). Secondary APS (HR 2.65, 95% CI 1.52–4.62) and recurrent thrombosis (HR 2.66, 95% CI 1.52–4.66) predicted severe damage but not damage. Diagnosis delay did not predict damage but predicted severe damage (HR 2.99, 95% CI 1.25–7.16), even after multivariate analysis (aHR 3.18, 95% CI 1.24–8.12). Conclusion In thrombotic APS, diagnosis delay is associated with increased number of thrombotic events and recurrent thrombosis, and is an independent predictor of severe organ damage.