SummaryObjectiveTo evaluate how the rating of the severity of sickness – as performed by the physician, nurse and patient – is associated with hospitalisation and acute morbidity.MethodsProspective observational study, performed in the emergency department of a tertiary hospital. Patients, physicians and nurses were interviewed separately after the first contact from 21 October through to 11 November 2013.ResultsOf 2426 presenting patients, 1861 were screened, and 1196 were included. A total of 299 (25%) were hospitalised, 504 (42%) suffered acute morbidity. In the univariate analysis, the physician's, nurse's and patient's rating of severity of sickness, expressed on a scale from 0 to 10, was significantly associated with hospitalisation (physicians: OR 1.61, 95% CI 1.50–1.73; nurses: OR 1.52, 1.41–1.64; patients: OR 1.16, 1.10–1.22), and with acute morbidity (OR 1.49, 1.40–1.59; OR 1.39, 1.30–1.48 and OR 1.05, 1.003–1.09 respectively). The area under the curve of the receiver operating characteristic curves was 0.77, 0.72 and 0.61 for hospitalisation, and 0.72, 0.68 and 0.54 for acute morbidity. The interrater reliability was estimated by the intraclass correlation, which was 0.49 for physician/nurse, 0.17 for nurse/patient and 0.07 for physician/patient. In a multivariable analysis model consisting of age, male sex, ethnic origin, ratings of severity of sickness, symptoms, ability to go home and hospitalisation during the preceding 12 months, only age, and the physician's and nurses' rating of severity of sickness remained significantly associated with both outcomes.ConclusionThe first impression of severity of sickness was associated with hospitalisation and morbidity.