[Can information on patients' whereabouts after an emergency department visit be used for analyses? A comparison between linked electronic health records and health claims data].

The aim of the research project ENQuIRE was to investigate the relationship between quality indicators of emergency departments (ED) and their relevance for patient outcomes. To this end, a data base with 12,067 electronic health records (MDAT) of treatment cases in 15 German ED from 2019 was established. For these MDAT, health claims data of Techniker Krankenkasse (TK) from various service sectors were also requested. In this paper, information from MDAT on the individual patient's admission to the hospital or visit to the ED as an outpatient is compared to health claims data. Based on this, the extent to which the health claims data can be used to replace non-usable information in MDAT is estimated.A selection was made of MDAT from the study population that allowed linkage with health claims data. Based on this, "Abgleich" (comparison) included MDAT for which reliable information on the patient's outpatient discharge, inpatient admission or other was available. By contrast, MDAT for which the information could not be used were included in "Ableitung" (derivation). Both in "Abgleich" as well as "Ableitung", health claims data of inpatient hospital treatments (Social act V § 301) and outpatient treatments accredited by statutory health insurance (Social act V § 295) were linked to MDAT.For 9,113 MDAT from the ENQuIRE study population, information on patient's whereabouts was available without linking health claims data. As part of "Abgleich", inpatient or outpatient billing cases could be identified for 5,450 MDAT. In direct comparison of both linked data sources, information on outpatient discharges and inpatient admissions aligned in more than 90 % of cases. As part of "Ableitung", information for 3,749 MDAT could be derived from health claims data. In combination of "Abgleich" and "Ableitung", the potential of health claims data comprised up to 9,199 outpatient treatments or inpatient admissions.Inpatient admissions following ED visits and outpatient treatments in ED can be meaningfully mapped in health claims data. Despite certain inconsistencies, health claims data matches the respective information in MDAT to a high degree. The potential with regard to the total number of cases is in ENQuIRE roughly similar when comparing both data sources. Which source of information is used for analyses therefore depends primarily on theoretical or methodological considerations.