Evaluating the representativeness and validity of Cosmos as a novel, large-scale, real-world data source for liver...

Liver transplant (LT) recipients experience a wide range of comorbidities, leading to frequent healthcare encounters. Until now, national registries, which have limited exposures and outcomes, and laborious small cohort studies have been the main data sources for LT research. Cosmos database offers electronic health record (EHR)-based insights into LT recipients at the national level with granular data. We evaluated whether Cosmos data is representative of the entire US LT recipient population. Using Cosmos (N=20,235) and the national Scientific Registry of Transplant Recipients (SRTR) (N=51,281), we identified adult, first-time LT recipients between July 2016 and December 2022. We compared demographics, clinical data, and mortality across datasets, calculating Kaplan-Meier survival estimates and multivariable Cox regressions. Recipient characteristics were highly comparable (eg, female: Cosmos=36.5% vs. SRTR=36.4%, Black: 6.8% vs. 7.2%; BMI: 28.5 kg/m 2 [24.8-32.9] vs. 28.2 [24.6-32.4]). Lab values were similar across cohorts, including MELD (24 [17-30] vs. 23 [16-30]). Transplant indications, donor characteristics, and 5-year survival (Cosmos 83.1% [82.3-83.8] vs. SRTR 80.9% [80.4-81.3]) were similar. The associations of clinical factors with survival were similar across both groups. The Cosmos database demonstrated acceptable generalizability to the general US LT recipient population, which may advance LT research through a better understanding of LT recipients' experiences and outcomes.