BACKGROUND: Pre-hospital emergency care requires proper categorization of emergency calls and assessment of emergency priority levels by the medical dispatchers. We investigated predictors for emergency call categorization as "unclear problem" in contrast to "symptom-specific" categories and the effect of categorization on mortality.

METHODS: Register-based study in a 2-year period based on emergency call data from the emergency medical dispatch center in Copenhagen combined with nationwide register data. Logistic regression analysis (N = 78,040 individuals) was used for identification of predictors of emergency call categorization as "unclear problem". Poisson regression analysis (N = 97,293 calls) was used for examining the effect of categorization as "unclear problem" on mortality.

RESULTS: "Unclear problem" was the registered category in 18% of calls. Significant predictors for "unclear problem" categorization were: age (odds ratio (OR) 1.34 for age group 76+ versus 18-30 years), ethnicity (OR 1.27 for non-Danish vs. Danish), day of week (OR 0.92 for weekend vs. weekday), and time of day (OR 0.79 for night vs. day). Emergency call categorization had no effect on mortality for emergency priority level A calls, incidence rate ratio (IRR) 0.99 (95% confidence interval (CI) 0.90-1.09). For emergency priority level B calls, an association was observed, IRR 1.26 (95% CI 1.18-1.36).

DISCUSSIONS: The results shed light on the complexity of emergency call handling, but also implicate a need for further improvement. Educational interventions at the dispatch centers may improve the call handling, but also the underlying supportive tools are modifiable. The higher mortality rate for patients with emergency priority level B calls with "unclear problem categorization" could imply lowering the threshold for dispatching a high level ambulance response when the call is considered unclear. On the other hand a "benefit of the doubt" approach could hinder the adequate response to other patients in need for an ambulance as there is an increasing demand and limited resources for ambulance services.

CONCLUSIONS: Age, ethnicity, day of week and time of day were significant predictors of emergency call categorization as "unclear problem". "Unclear problem" categorization was not associated with mortality for emergency priority level A calls, but a higher mortality was observed for emergency priority level B calls.