Evaluating the effect of driving distance to the nearest higher level trauma centre on undertriage: a cohort study.

Background: It is of great importance that emergency medical services professionals transport trauma patients in need of specialised care to higher level trauma centres to achieve optimal patient outcomes. Possibly, undertriage is more likely to occur in patients with a longer distance to the nearest higher level trauma centre. This study aims to determine the association between driving distance and undertriage.

Method: This prospective cohort study was conducted from January 2015 to December 2017. All trauma patients in need of specialised care that were transported to a trauma centre by emergency medical services professionals from eight ambulance regions in the Netherlands were included. Patients with critical resource use or an Injury Severity Score ≥16 were defined as in need of specialised care. Driving distance was calculated between the scene of injury and the nearest higher level trauma centre. Undertriage was defined as transporting a patient in need of specialised care to a lower level trauma centre. Generalised linear models adjusting for confounders were constructed to determine the association between driving distance to the nearest higher level trauma centre per 1 and 10 km and undertriage. A sensitivity analysis was conducted with a generalised linear model including inverse probability weights.

Results: 6101 patients, of which 4404 patients with critical resource use and 3760 patients with an Injury Severity Score ≥16, were included. The adjusted generalised linear model demonstrated a significant association between a 1 km (OR 1.04; 95% CI 1.04 to 1.05) and 10 kilometre (OR 1.50; 95% CI 1.42 to 1.58) increase in driving distance and undertriage in patients with critical resource use. Also in patients with an Injury Severity Score ≥16, a significant association between driving distance (1 km (OR 1.06; 95% CI 1.06 to 1.07), 10 km (OR 1.83; 95% CI 1.71 to 1.95)) and undertriage was observed.

Conclusion: Patients in need of specialised care are less likely to be transported to the appropriate trauma centre with increasing driving distance. Our results suggest that emergency medical services professionals incorporate driving distance into their decision making regarding transport destinations, although distance is not included in the triage protocol.