Morbidity and mortality in primary versus secondary antiphospholipid syndrome: A single-center study using the 2023 ACR/EULAR criteria.

ObjectiveTo evaluate differences in morbidity and mortality between patients with primary antiphospholipid syndrome (PAPS) and APS secondary to systemic lupus erythematosus (SAPS), classified according to the 2023 ACR/EULAR APS criteria.MethodsA single-center retrospective observational study including consecutive adult patients evaluated for suspected APS, retrospectively classified according to the 2023 ACR/EULAR APS criteria. Those patients who were included were categorized as SAPS based on the presence of concomitant SLE, defined using the 2012 Systemic Lupus International Collaborating Clinics criteria. Demographic, clinical, laboratory, and outcome data were extracted from medical records. Group comparisons were performed using t-tests, chi-square or Fisher's exact tests. Multivariable Cox regression was used to identify factors associated with mortality.ResultsOf 432 patients who were screened, 210 (48.6%) fulfilled the 2023 ACR/EULAR criteria and were included, comprising 151 (71.9%) with PAPS and 59 (28.1%) with SAPS. Compared with PAPS, SAPS patients were more frequently female (91.7% vs 65.6%, p < 0.001), of younger age at first APS-related event (34.2 vs 43.1 years, p < 0.001), and had a higher prevalence of renal disease (33. 9% vs 6.0%, p < 0.001). Rates of venous, arterial, recurrent thrombosis, and obstetric manifestations were similar between groups. CAPS and overall mortality were higher in SAPS (11.9% vs 2.7%, p = 0.01; 22.0% vs 10.6%, p = 0.045, respectively). In multivariable Cox regression, increasing age at first event, SAPS, and renal disease were independently associated with increased mortality (adjusted HR 1.1, 5.28, and 3.16, respectively).ConclusionSAPS is associated with higher mortality and increased CAPS risk, emphasizing the adverse prognostic impact of concomitant SLE and the need for tailored risk stratification.