Data sources and linkage

This study analyses Fee-for-Service Medicare patients undergoing ERCP between January 2015 and December 2021. All Fee-for-Service Medicare Inpatient, Outpatient and Carrier files for patients undergoing ERCP at US hospitals and ambulatory surgery centres (ASCs) were eligible. Inpatient and outpatient procedures were included. Medicare is a federal programme that provides health insurance to all Americans aged 65 years and older and individuals with disabilities.

Generalisability of the Medicare results was estimated by including all-payer information from five states (ie, Florida, Georgia, Iowa, Maryland and Wisconsin) in 2017. State data were made available through Agency for Healthcare Research and Quality and Healthcare Cost and Utilisation Project.¹⁷ These states were selected because they make links available between hospital outpatient, hospital-affiliated ASC and inpatient records using individual patient identifiers that are consistent across the files. The states provide scrambled service utilisation dates. The unique encrypted patient identifiers are valid during a single calendar year.