Predictive capability of the injury severity score versus the new injury severity score in the categorization of the severity of trauma patients: a cross-sectional observational study

Purpose The AIS scale is a measurement tool for single injuries. The ISS is considered the gold standard for determining the severity of injured patients, and the NISS was developed to improve the ISS with respect to loss of information, as well as to facilitate its calculation. The aim of this study was to analyse what injury severity measure, calculated according to the Abbreviated Injury Scale (AIS), 1998 and 2005 (update 2008) versions, performs better with mortality, cost and hospital length of stay healthcare indicators. Methods This cross-sectional observational study was carried out between February 1st 2012 and February 1st 2013. Inclusion criteria were injured patients due to external causes admitted to trauma service through the emergency department. Manual coding of all injuries was performed and ISS and NISS scores were calculated for both versions of the AIS scale. Severity was then compared to mortality (in-hospital and at 30 days), healthcare cost, and length of hospital stay. Results The index with the best predictive capability for in-hospital mortality was NISS 05 (AUC = 0.811). There was a significant increase in hospital stay and healthcare cost in the most severe patients in all indexes, except for ISS 05. Conclusions NISS is found to be an index with higher predictive capability for in-hospital mortality and correlates better to length of hospital stay and healthcare cost.