Our rate of over triage is 78 % and our rate of under triage is 4.6 %. There are published recommendation rates of over and under triage in pre-hospital trauma field medicine by the American College of Surgeons Committee on Trauma (5–10 % of under triage and 30–50 % of over triage) [20], but we are still missing such consensus on acceptable rates and objectives in medical dispatch. Thirty-one experts met in 2004 to establish standards on EMS studies, but specifically no agreement was found on over and under triage in particular [21].

Some looked for concordance between dispatch priorities and emergency department (ED) evaluation [22], or between dispatch, EMS and ED [23]. We decided to compare dispatch priorities and EMS field findings only, as EDs’ evaluation cannot take into account any significant change in the patient’s condition due to time and pre-hospital intervention. Priority dispatch should be evaluated by the first professional on site, so the impact of elapsed time from dispatch to clinical evaluation is minimal. Treatments provided by EMS may contribute to the improvement of the patient’s clinical condition, which will also interfere with the evaluation by ED personal of dispatch priority.

Benchmarking remains difficult even when looking only at studies that did compare dispatch priorities and EMS findings rather than ED evaluations. Dispatch centres (CBD, MPDS, physician dispatch) and EMS systems (two or three tiers) are very heterogeneous. Although all previous studies have dealt with the same metric issue (high versus low-acuity cases) there is no consensus on their definition. Therefore criteria to define a concordance between dispatch priority and the clinical findings on the field by EMS (gold standard) differ widely.

Table 5 presents results from previous studies dispatch over and under triage. Those examples show that not only are dispatch criteria different between studies, but also case acuity measurement tools by on field EMS. Therefore it is not possible to conclude that one system may be more efficient than another, whatever rates of over and under triage are published. Nevertheless, it is of prime importance for dispatch centres to publish their results as this may allow benchmarking and, with time, permit the reaching of an international consensus on dispatch accuracy.

Scott et al. remind us that during the seventies, studies showed that the outcome of non-traumatic cardiac arrests was linked to rapid EMS dispatch [24, 25]. This observation paved the way to the ‘eight-minutes response’ that all dispatch centres within United States try to achieve for Advanced Life Support interventions. However, according to a 2002 systematic review [26], and to Snooks et al. when defining the highest priorities for research in emergency pre-hospital care in 2009, there is still insufficient evidence to generalize the effect of the prioritization of emergency ambulances on patient outcome other than cardiac arrest, and therefore it may not be a useful indicator [1, 27].

The future of dispatching may rely on a very structured interview based on questions with high PPV to avoid under triage, or NPV to avoid over triage for life-threatening conditions, combined with sophisticated computer algorithms to estimate better the patient’s life threat risk [28]. In a study from Japan, this system resulted in an over triage’s rate of 35 % and an under triage of less than 1 % for cases when looking specifically at cardio-pulmonary arrest cases (sensitivity 80.2 % (95 % CI: 78.6–81.8 %), specificity 96.0 % (95 % CI: 95.8–96.1 %), PPV 42.6 % (95 % CI: 41.1–44.0 %), and NPV 99.2 % (95 % CI: 99.2–99.3 %) respectively) [29].