Implementing a nationwide criteria-based emergency medical dispatch system: a register-based follow-up study.

Background: A criteria-based nationwide Emergency Medical Dispatch (EMD) system was recently implemented in Denmark. We described the system and studied its ability to triage patients according to the severity of their condition by analysing hospital admission and case-fatality risks.

Methods: This was a register-based follow-up study of all 1-1-2 calls in a 6-month period that were triaged according to the Danish Index - the new criteria-based dispatch protocol. Danish Index data were linked with hospital and vital status data from national registries. Confidence intervals (95%) for proportions with binomial data were computed using exact methods. To test for trend the Wald test was used.

Results: Information on level of emergency according to the Danish Index rating was available for 67,135 patients who received ambulance service. Emergency level A (urgent cases) accounted for 51.4% (n = 34,489) of patients, emergency level B for 46.3% (n = 31,116), emergency level C for 2.1% (n = 1,391) and emergency level D for 0.2% (n = 139). For emergency level A, the median time from call receipt to ambulance dispatch was 2 min 1 s, and the median time to arrival was 6 min 11 s. Data concerning admission and case fatality was available for 55,270 patients. The hospital admission risk for emergency level A patients was 64.4% (95% CI = 63.8-64.9). There was a significant trend (p < 0.001) towards lower admission risks for patients with lower levels of emergency. The case fatality risk for emergency level A patients on the same day as the 1-1-2 call was 4.4% (95% CI = 4.1-4.6). The relative case-fatality risk among emergency level A patients compared to emergency level B-D patients was 14.3 (95% CI: 11.5-18.0).

Conclusion: The majority of patients were assessed as Danish Index emergency level A or B. Case fatality and hospital admission risks were substantially higher for emergency level A patients than for emergency level B-D patients. Thus, the newly implemented Danish criteria-based dispatch system seems to triage patients with high risk of admission and death to the highest level of emergency. Further studies are needed to determine the degree of over- and undertriage and prognostic factors.