Data resource profile: State Inpatient Databases

IEA International Epidemiological Association International Journal of Epidemiology, 2019, 1742–1742h doi: 10.1093/ije/dyz117 Advance Access Publication Date: 6 July 2019 Data Resource Profile Data Resource Profile Data resource profile: State Inpatient Databases David Metcalfe,1* Cheryl K Zogg,2 Elliott R Haut,3 Timothy M Pawlik,4 Adil H Haider5 and Daniel C Perry1 Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK, 2Yale School of Medicine, New Haven, CT, USA, 3Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, MD, USA, 4Wexner Medical Center, The Ohio State University, Columbus, OH, USA and 5Center for Surgery and Public Health, Harvard Medical School, Boston, MA, USA *Corresponding author. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK. E-mail: Editorial decision 14 May 2019; Accepted 23 May 2019 Data resource basics Scope The State Inpatient Databases (SIDs) comprise a collection of state-specific encounter-level administrative claims from 32/50 states in the USA. These databases are maintained by the US Agency for Healthcare Research and Quality (AHRQ) as a part of the organization’s Healthcare Cost and Utilization Project (HCUP). As part of a family of six other HCUP databases (Table 1), the SIDs represent the largest collection of longitudinal hospital care data in the USA inclusive of all insurance payers (e.g. Medicare, Medicaid, private insurance and uninsured) and all patient ages. Taken together, the SIDs capture more than 97% of all eligible hospital discharges within each state. Purpose of data collection Originally created as the ‘Agency for Health Care Policy and Research’, AHRQ was established by the US Omnibus Budget Reconciliation Act of 1989 with the purpose of enhancing the ‘quality, appropriateness, and effectiveness of health care services [. . .] through the establishment of a broad case of scientific research’.1 In particular, the Act required that databases be created to support healthcare research. The HCUP-family of databases were, therefore, established as a federal-state–industry partnership sponsored by AHRQ in order to ‘enable research on a broad range of health policy issues, including cost and quality of health services, medical practice patterns, access to health care programmes, and outcomes of treatment at the national, state and local market levels’.2 The HCUP SIDs maintain data expressly for research purposes dating back to 1990. Structure The SIDs share a common structure, although the precise list of available data elements vary slightly by state and calendar year. Differences in key variables used to link SID data are presented in Table 2. The SIDs are organized by calendar year based on the date of hospital discharge. The data for each SID year (e.g. Florida 2014) are presented in up to five separate files: core, charges, American Hospital Association (AHA) linkage, Diagnosis Related Groups (DRGs), and disease severity. The core file contains the discharge-level data elements that make up the majority of each SID. Some core data elements are universal [e.g. AGE, DISPUNIFORM (discharge disposition), DX1-DXn (primary and secondary diagnosis codes), PR1-PRn (primary and secondary procedure codes) and LOS (length of stay)]. Others vary by state [e.g. ZIP (patient residential zip code), RACE (patient race/ethnicity), and visitLink/DaysToEvent (variables needed for longitudinal patient tracking)]. The charges file contains information needed to convert total hospital charges (core: TOTCHG) into estimated costs incurred. The AHA linkage file permits linkage to data from the AHA Annual Survey Database, which contains C The Author(s) 2019; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association V 1742 1 International Journal of Epidemiology, 2019, Vol. 48, No. 6 1742a Table 1. Family of Healthcare Cost and Utilization Project (HCUP) databases Abbreviation National US databases National (Nationwide) Inpatient Sample NIS Kids’ Inpatient Database KID Nationwide Emergency Department Sample NEDS Nationwide Readmissions Database NRD State-specific US databases State Inpatient Databases SID State Ambulatory Surgery and Services Databases SASD State Emergency Department Databases SEDD Content summary Data dictionary Cross-sectional subset of national inpatient stays since 1988, needs to be nationally weighted Cross-sectional subset of paediatric inpatient stays since 1997, released every 3 years, needs to be nationally weighted Cross-sectional subset of emergency department visits since 2006, needs to be nationally weighted Longitudinal linking within individual calendar years of inpatient claims from a subset of longitudinal SIDs since 2010, needs to be nationally weighted https://www.hcup-us.ahrq.gov/db/na tion/nis/nisdde.jsp https://www.hcup-us.ahrq.gov/db/na tion/kid/kiddde.jsp https://www.hcup-us.ahrq.gov/db/na tion/neds/nedsdde.jsp https://www.hcup-us.ahrq.gov/db/na tion/nrd/nrddde.jsp All state encounter-level inpatient claims (same hospital emergency department admissions, incoming transfers) since 1990, some states longitudinal across calendar years, AHA and SASD/SEDD external linkage possible All state encounter-level ambulatory/outpatient claims at hospital-owned facilities since 1997, some states longitudinal across calendar years, AHA and SID/SEDD external linkage possible All state encounter-level emergency department claims (non-inpatient admissions, discharged as transfers) since 1999, some states longitudinal across calendar years, AHA and SASD/ SID external linkage possible https://www.hcup-us.ahrq.gov/db/ state/siddist/siddistvarnote2015. jsp https://hcup-us.ahrq.gov/db/state/ sasddist/sasddistvarnote2015.jsp https://www.hcup-us.ahrq.gov/db/ state/sedddist/sedddistvar note2015.jsp AHA, American Hospital Association Annual Survey Database (hospital-level information on additional institution-specific parameters). Table 2. Availability of key linkage variables within the 2015 SIDs, the most complete year of data available in HCUP to date Element AHAID DaysToEvent HOSPID MDNUM1_R visitLink AR AZ CO DC FL GA HI IA KS KY MA MD ME MI MN MS NC NE NJ NM NV NY OR RI SC SD UT VT WA WI WV þ þ þ – þ þ þ þ þ – þ – þ þ – – – þ þ – þ þ þ þ þ – – þ – þ þ – þ – – þ þ þ þ þ þ – þ – – þ – þ – – þ þ þ – þ þ þ þ þ þ – – þ – – – – þ þ – þ – þ – – þ þ þ þ þ þ – þ – – þ þ þ – þ þ – þ þ – – þ þ þ þ þ – þ þ – þ þ þ þ þ þ – þ – – þ – þ þ – – – – – – – – þ þ – þ þ þ þ þ þ þ þ – þ þ þ þ þ þ þ þ þ – þ þ – þ – – AHAID, permits linkage to the AHA Annual Survey Database; DaysToEvent, time to event variable using a randomly selected start date and always used in conjunction with visitLink; HOSPID, unique identifier for individual hospitals; MDNUM1_R, uniq (...truncated)