Abstract TP149: Prevalence of Antiphospholipid Syndrome in Acute Stroke: A Nationwide Analysis

Introduction: Antiphospholipid syndrome(APS) is an underrecognized cause of acute ischemic stroke(AIS). Early diagnosis of APS is essential as proper secondary prevention with vitamin K antagonists can reduce risk of recurrent stroke. Though APS is thought to be an uncommon stroke etiology, the true prevalence of APS in AIS is unknown. In this study, we aimed to (1)determine the prevalence of APS in AIS and (2)characterize its clinical phenotype. Methods: Using the National Inpatient Sample(NIS), we conducted a large, retrospective cross-sectional study of a stratified sample of all hospital admissions in the United States from 2016 to 2022. All adult patients hospitalized with AIS were identified and separated into two groups based on the presence or absence of a diagnosis of APS. The prevalence of APS in AIS was calculated using the NIS derived discharge weights. Demographic, risk factors, acute treatments and in-hospital outcomes were compared. Results: Of 4,407,923 admissions for AIS between 2016 and 2022, 14,350 patients had AIS with APS, a 0.3% prevalence among all AIS patients. This prevalence increased 4.7 fold for stroke in young patients (age 18-50, prevalence 1.4%). APS with AIS patients were more likely to be younger(55.0 vs 69.8, p value<0.05), female(61.9% vs 49.4%, p value<0.05), and had fewer cerebrovascular risk factors including hypertension(73.0% vs 83.6%, p value<0.05), hyperlipidemia(46.4% vs 58.6%, p value<0.05) and diabetes(26.7% vs 39.5%, p value<0.05). These patients had longer hospital stays(10.2 vs 6.3 days, p value<0.05), worse illness severity (extreme loss 31.0% vs 21.5%, p value<0.05) and higher hospital costs($150,805 vs $90,207, p value<0.05). A large proportion of APS with AIS(57.7%) had another stroke etiology diagnosis- atrial fibrillation(14.6%), extracranial atherosclerosis(12.9%) and congenital heart disease(9.0%) most frequently. The majority of cases(84.2%) were diagnosed at teaching hospitals. Conclusions: In this nationally representative cohort, APS prevalence was 1 in 333 AIS hospitalizations, with markedly higher prevalence of 1 in 71 in young stroke patients. Though uncommon, the concentration of diagnoses at teaching hospitals suggests many cases are undiagnosed. APS related stroke patients have a distinct clinical phenotype: younger age, fewer stroke risk factors and greater disease burden. These findings highlight the importance of heightened diagnostic consideration for APS, particularly in young stroke patients.