Table 2.

Existing reference standards for major trauma.

Category	Anatomical	Resource	Prognosis	Composite
Examples	Injury severity score New injury severity score Abbreviated Injury Scale Swiss highly specialised medicine regulations	US consensus definitions Vassallo definition	Revised trauma score TRISS TARN prediction model New revised trauma score MGAP Emergency Trauma Score A Severity Characterisation of Trauma (ASCOT) ICD-based injury severity score (ICISS) Trauma Mortality Prediction Model Polytrauma score Acute Trauma Index CRAMS Pre-hospital Index (PHI) Triage Revised Trauma Score (T-RTS) Physiologic Severity Score (PSS) Mechanism, Glasgow Coma Scale, Age and Arterial Pressure (MGAP) Modified Rapid Emergency Medicine Score (mREMS) Kampala Trauma Score (KTS) Berlin polytrauma criteria	Current MATTS reference standard German trauma society criteria Ad hoc composite measures, e.g. combination of ISS, intensive care unit admission and any non-orthopaedic surgery within 24 hours
Advantages of defining need for expedited MTC care	Theoretical: Simple Objective Operational: Readily available for research purposes from trauma registries	Theoretical: Captures patients with low ISS who need urgent trauma interventions Reflects critical determinants of benefits of MTC care Operational: Readily available for research purposes from trauma registries	Theoretical: Objective Presents mortality risk range/threshold Operational: Information for calculation available from trauma registries	Theoretical: Minimises the disadvantages of single domain reference standards Operational: Information for calculation available from trauma registries
Disadvantages of defining need for expedited MTC care	Theoretical: Some apparently less severe injuries benefit from urgent MTC interventions Modifiers of injury severity excluded, e.g. comorbidities Injury severity not fully captured, e.g. GCS score in TBI Futility excluded (except AIS 6 un-survivable injuries) Patient values excluded Operational: Influenced by degree of investigation	Theoretical: Some serious injuries benefiting from MTC care may not need resource-based interventions Patient values excluded Operational: Subject to variability in medical decision-making and hospital expertise Potential confounding effect from concomitant acute medical events	Theoretical: Significance of individual injuries excluded Resource use excluded Futility excluded Patient values excluded Operational: Often complex Generally poor predictive performance Often unvalidated	Theoretical: Might compound the disadvantages of single domain reference standard Operational: Increased complexity