Characterizing injury severity in nonaccidental trauma: Does Injury Severity Score miss the mark?

backgroundChildren suffering nonaccidental trauma (NAT) are at high risk of death. It is unclear whether markers of injury severity for trauma center/system benchmarking such as Injury Severity Score (ISS) adequately characterize this. Our objective was to evaluate mortality prediction of ISS in children with NAT compared with accidental trauma (AT).

methodsPediatric patients younger than 16 years from the Pennsylvania state trauma registry 2000 to 2013 were included. Logistic regression predicted mortality from ISS for NAT and AT patients. Multilevel logistic regression determined the association between mortality and ISS while adjusting for age, vital signs, and injury pattern in NAT and AT patients. Similar models were performed for head Abbreviated Injury Scale (AIS). Sensitivity analysis examined impaired functional independence at discharge as an alternate outcome.

resultsFifty thousand five hundred seventy-nine patients were included with 1,866 (3.7%) NAT patients. Nonaccidental trauma patients had a similar rate of mortality at an ISS of 13 as an ISS of 25 for AT patients. Nonaccidental trauma patients also have higher mortality for a given head AIS level (range, 1.2-fold to 5.9-fold higher). Injury Severity Score was a significantly greater predictor of mortality in AT patients (adjusted odds rations [AOR], 1.14; 95% confidence interval [CI], 1.13-1.15; p < 0.01) than NAT patients (AOR, 1.09; 95% CI, 1.07-1.12; p < 0.01) per 1-point ISS increase, while head injury was a significantly greater predictor of mortality in NAT patients (AOR, 3.48; 95% CI, 1.54-8.32; p < 0.01) than AT patients (AOR, 1.21; 95% CI, 0.95-1.45; p = 0.12). Nonaccidental trauma patients had a higher rate of impaired functional independence at any given ISS or head AIS level than AT patients.

conclusionNonaccidental trauma patients have higher mortality and impaired function at a given ISS/head AIS than AT patients. Conventional ISS thresholds may underestimate risk and head injury is a more important predictor of mortality in the NAT population. These findings should be considered in system performance improvement and benchmarking efforts that rely on ISS for injury characterization. LEVEL OF EVIDENCE: Epidemiologic study, level III.