Abstract Body: Introduction
Patients suffering from transient ischemic attack (TIA) are at high risk of ischemic stroke (IS). This study describes clinical characteristics and outcomes in patients with a first non-cardioembolic TIA.

Methods
Using two US administrative claims databases (MarketScan and Optum’s de-identified Clinformatics® Data Mart Database [CDM]) converted to the Observational Medical Outcomes Partnership (OMOP) common data model, we conducted an observational, retrospective cohort study of adults with a first diagnosis of non-cardioembolic TIA between 2012 and 2022. Demographic and clinical characteristics were described at baseline, and incidence rates of IS, intracranial bleeding, and bleeding leading to hospitalization with sensitivity analyses at different time points were calculated.

Results
Overall, 203,757 patients were included in the study, 97,481 from MarketScan, 106,276 from CDM. Mean age was 62 years in MarketScan and 72 years in CDM. Patients were mostly women (57.6% in MarketScan, 59.3% in CDM). At baseline, prevalence of comorbidities was high (hypertension 66% and 84%, hyperlipidemia 53% and 75%, coronary artery disease 18% and 31%, diabetes 25% and 38% in MarketScan and CDM, respectively). Median follow-up time was 569 days in MarketScan and 716 days in CDM. At 1 year follow-up, incidence rates per 100 person-years of IS, intracranial bleeding, and bleeding leading to hospitalization were 10.9, 0.9, and 4.2, respectively, in MarketScan and 20.2, 1.6, and 7.6 respectively, in CDM. Sensitivity analyses showed that most IS events occurred within 7 days of the index event. Additional event rates and sensitivity analyses are shown in Table 1.

Conclusion
Results from two US claims databases show that the annual risk of IS is higher than expected following a first TIA diagnosis, especially when including the first 7 days in the ascertainment. Implementation of guideline directed antiplatelet therapies, or new antithrombotic strategies, is needed.