Validation of a relative head injury severity scale for pediatric trauma

BACKGROUND: Brain injury is the most important independent predictor of mortality and morbidity in pediatric trauma. The Glasgow Coma Score (GCS) is the commonly used clinical instrument to assess brain injury. However, the GCS or one of its components is often not applicable in children under a certain age or cannot be computed reliably because of the patient's condition or the circumstances surrounding resuscitation efforts. This limits its usefulness in statistical models of trauma outcomes, which rely on complete data collection and entry into trauma registries. This study provides evidence validating use of a relative head injury severity scale (RHISS) derived from available International Classification of Diseases, 9th Revision (ICD-9) diagnosis codes to stratify degree of head injury. METHODS: The patient population was derived from the National Pediatric Trauma Registry (NPTR;1994-2001). Survival Risk Ratios (SRRs) were computed for each head injury ICD-9 code. ICD-9 diagnosis codes related to head injury were then assigned to a RHISS category based on duration of loss of consciousness, location of skull fracture, or both: 0 = none; 1 = mild; 2 = moderate, or 3 = severe head injury. Analysis of variance compared mean SRRs across RHISS categories. Each patient was then assigned to a RHISS category based on their single worst ICD-9 head injury code. Logistic regression analysis was used to predict mortality based on New Injury Severity Score (NISS), whether the patient had been intubated, RHISS, and the Abbreviated Injury Score (AIS) for head and neck injuries. RESULTS: GCS score was missing for 96% of nonsurvivors in the NPTR. Mean SRRs differed significantly (p <0.001) among ICD-9 codes assigned to each RHISS category, as follows (Mean ± SD): RHISS (0) = 0.93 ± 0.16; RHISS (1) = 0.89 ± 0.22; RHISS (2) = 0.85 ± 0.26; RHISS (3) = 0.55 ± 0.35. Logistic regression identified RHISS as an independent significant predictor (p <0.01) of mortality. CONCLUSION: RHISS is a valid index of degree of head injury in the pediatric trauma population. Unlike GCS, RHISS is more likely to be available in trauma registries, and can be computed from administrative data. RHISS provides a feasible and valid method for quantifying the degree of brain injury in statistical models of pediatric trauma outcome.