[Routine Data from Emergency Departments: Varying Documentation Standards, Billing Modalities and Data Custodians at an Identical Unit of Care].

Background: Currently, there is a big need for data on emergency department (ED) utilization in Germany. One reason is the ongoing reorganisation of emergency care. Possible sources are routine data that are being collected based on legal regulations. Different payers and compensation systems have their own requirements for data collection.

Methodological Challenges: Due to the sectoral separation of health care services, there is no dataset or data holder to provide information on all ED treatments in Germany. From an administrative point of view, emergency care in Germany is considered ambulatory outpatient or inpatient care from the time point of admission to the ED. In contrast, clinical decision about inpatient admission can sometimes only be made towards the end of emergency care. EDs themselves cannot be identified in claims data; only the medical discipline (e. g. surgery) is classified. In the case of outpatient treatment, reimbursed by the Association of Statutory Health Insurance Physicians, at least one coded diagnosis (ICD) has to be recorded, accompanied by an additional code for the likelihood of this diagnosis. In case of multiple ICDs, a primary diagnosis cannot be specified. In the case of in-hospital treatment, an admission diagnosis must be recorded. After completion of hospital treatment, the main diagnosis and possibly secondary diagnoses are transferred to the respective health insurance fund. The statutory occupational accident insurance has its own requirements.

Solutions: Depending on the research question and study design, different approaches are required. If data are queried directly in emergency departments or hospitals, additional information on the designated data holder and billing mode is crucial. When using health insurance data from inpatient care, the identification of emergency departments can be estimated on the basis of the reason for hospital admission and defined "unique" emergency ICDs. The case-related hospital statistics has its own limitations, but includes inpatients of all payers.

Discussion: Differing requirements for the administrative documentation cause a high workload in emergency departments. A standardised data collection system for all payers for inpatient and outpatient emergency care is recommended. This would contribute to the creation of valid and comparable datasets. The introduction of a particular identifier for EDs in claims data would enhance health services research.