Trauma patients constitute a heterogeneous population, making trauma research and outcome comparison over time and between contexts difficult but important (5). Accounting for factors such as selection bias, difference in care and case mix is crucial for correct conclusions (6,7).To enable this several tools or scores have been developed including the Injury Severity Score (ISS) and the Trauma and Injury Severity Score (TRISS) (8,9). The use of these scores as part of quality improvement programmes has been associated with improved trauma care (10).