Incorporating age improves the Glasgow Coma Scale score for predicting mortality from traumatic brain injury

BACKGROUND: The Glasgow Coma Scale (GCS) score has been adapted into categories of severity (mild, moderate, and severe) and are ubiquitous in the trauma setting. This study sought to revise the GCS categories to account for an interaction by age and to determine the discrimination of the revised categories compared with the standard GCS categories. METHODS: The American College of Surgeons National Trauma Data Bank registry was used to identify patients with traumatic brain injury (TBI; ICD-9 codes 850–854.19) who were admitted to participating trauma centers from 2010 to 2015. The primary exposure variables were GCS score and age, categorized by decade (teens, 20s, 30s…, 80s). In-hospital mortality was the primary outcome for examining TBI severity/prognostication. Logistic regression was used to calculate the conditional probability of death by age decade and GCS in a development dataset (75% of patients). These probabilities were used to create a points-based revision of the GCS, categorized as low (mild), moderate, and high (severe). Performance of the revised versus standard GCS categories was compared in the validation dataset using area under the receiver operating characteristic (AUC) curves. RESULTS: The final population included 539,032 patients with TBI. Age modified the performance of the GCS, resulting in a novel categorization schema for each age decile. For patients in their 50s, performance of the revised GCS categories mirrored the standard GCS categorization (3–8, 9–12, 13–15); all other revised GCS categories were heavily modified by age. Model validation demonstrated the revised GCS categories statistically significantly outperformed the standard GCS categories at predicting mortality (AUC: 0.800 vs 0.755, p<0.001). The revised GCS categorization also outperformed the standard GCS categories for mortality within pre-specified subpopulations: blunt mechanism, isolated TBI, falls, non-transferred patients. DISCUSSION: We propose the revised age-adjusted GCS categories will improve severity assessment and provide a more uniform early prognostic indicator of mortality following traumatic brain injury. LEVEL OF EVIDENCE: III epidemiologic/prognostic.