Abstract Body (Do not enter title and authors here): Background: Administrative claims data are increasingly used for post-marketing surveillance of drugs and medical devices, though data reliability remains uncertain. Given their associated morbidity and mortality, stroke events are particularly important to monitor for cardiovascular therapies such as transcatheter left atrial appendage occlusion (LAAO). However, there are limited data comparing stroke events in contemporary claims data to events reported in large nationwide registries with comprehensive data collection.

Aim: To compare stroke events in Medicare claims data with adjudicated registry-reported events in the National Cardiovascular Data Registry Left Atrial Appendage Occlusion (LAAO) Registry.

Methods: LAAO Registry data were linked with 2016-2022 Medicare inpatient claims. Primary diagnosis ICD-10 codes from inpatient hospitalizations were compared to adjudicated registry-reported ischemic and hemorrhagic stroke events occurring after discharge with up to two years of follow-up. In multiple secondary analyses, primary and secondary diagnosis codes were counted as events in claims data and patients with prior history of stroke were also excluded.

Results: The cohort included 71,043 adults ≥65 years old in the LAAO Registry with inpatient Medicare data. Following LAAO hospitalization discharge, there were 1405 claims-based and 1308 registry-reported total stroke events. Sensitivity and positive predictive value (PPV) of claims for identifying registry-reported events were 60.8% and 50.5% for ischemic stroke (kappa statistic 0.55), 42.7% and 50.5% for hemorrhagic stroke (kappa 0.46), and 58.1% and 54.1% for all stroke (kappa 0.55), respectively. Inclusion of secondary diagnosis codes improved sensitivity of claims (70.3% for ischemic stroke, 53.9% for hemorrhagic stroke and 67.0% for all stroke), but PPV decreased (44.8% for ischemic stroke, 34.8% for hemorrhagic stroke and 47.8% for all stroke). Specificity and negative predictive values of claims data were >98% for all stroke types. Findings were similar after excluding patients with prior history of stroke (Table).

Conclusions: Among Medicare patients in the LAAO Registry, administrative claims data had moderate agreement with adjudicated registry-reported stroke events. Claims data may not reliably capture all stroke events in real-world practice, and additional event ascertainment methods may be needed to ensure accurate assessment of stroke in post-marketing surveillance efforts.