The population comprised all activations between 1st November 2020 and 31st December 2021. All contacts were prospectively registered in the patient administrative system at OUH with a procedure code and a conclusive International classification of Diseases (ICD-10) diagnosis. Information regarding person identifiers, age, sex, dates and times of visits, final diagnoses and hospital admissions were extracted based on specific procedure codes. For the OUH registered data, we recorded the dates and times (index), hospital admissions, all acute hospital contacts within the past 2 years before the index visits and related discharge diagnoses until 30 days following the visits. The data were merged on an individual level and stored, prepared and assigned on a secure encrypted and logged server via OPEN Analyse, which is a secure analysis environment in the Region of Southern Denmark [20 ].
The following detailed information was registered on-site in the nursing homes for two time periods by the ED consultant: level of acuity of the dispatched ambulance and the ED-based acute care service (response levels: high acuity, moderate acuity, low acuity and very low acuity); information regarding the dispatch of ambulances; IV fluid therapy; procedures performed (point-of-care analyses and ultrasonography); medical treatment initiated; and any ensuing treatment at the nursing home prescribed by the ED consultant. The medical treatments initiated included intravenous antibiotics, analgesics, sedatives, diuretics and other medical treatments.