Introduction Secondary triage at a major incident allows for a more detailed assessment of the patient. In the UK, the Triage Sort (TSO) is the preferred method, combining GCS, systolic BP (SBP) and RR to categorise Priority 1 casualties. The Shock Index (SI) is calculated by dividing HR by SBP (HR/SBP). This study examines whether SI is better at predicting need for life-saving intervention (LSI) following trauma than TSO.

Methods A prospective observational study was undertaken. Physiological data and interventions performed in the Emergency Department and operating theatre were prospectively collected for 482 consecutive adult trauma patients presenting to Camp Bastion, Afghanistan, over a 6-month period. A patient was deemed to have required LSI if they received any intervention from a set described previously.

Results Complete data were available for 345 patients (71.6%). Of these, 203 (58.8%) were gold standard P1, and 142 (41.2%) were non-P1. The TSO predicted need for LSI with a sensitivity of 58.6% (95% CI 51.8% to 65.4%) and specificity of 88.7% (95% CI 83.5% to 93.9%). Using an SI cut-off >0.75 provided greater sensitivity of 70.0% (95% CI 63.6% to 76.3%) while maintaining an acceptably high (although lower than TSO) specificity of 74.7% (95% CI 67.5% to 81.8%). At this SI cut-off, there was evidence of a difference between TSO and SI in terms of the way in which patients were triaged (p<0.0001).

Discussion Our study showed that a SI >0.75 more accurately predicted the need for LSI, while maintaining acceptable specificity. SI may be more useful than TSO for secondary triage in a mass-casualty situation; this relationship in civilian trauma should be examined to clarify whether these results can be more widely translated into civilian practice.

Project registration number RCDM/Res/Audit/1036/12/0050.