The Glasgow Coma Scale (GCS) score is widely used to assess patients with head injury but has been criticized for its complexity and poor interrater reliability. A 3-point Simplified Motor Score (SMS) (defined as obeys commands=2, localizes pain=1, and withdraws to pain or worse=0) was created to address these limitations. Our goal is to validate the SMS in the out-of-hospital setting, with the hypothesis that it is equivalent to the GCS score for discriminating brain injury outcomes.

This was a secondary analysis of an urban Level I trauma registry. Four outcomes and their composite were studied: emergency tracheal intubation, clinically meaningful brain injury, need for neurosurgical intervention, and mortality. The out-of-hospital GCS score and SMS were evaluated by comparing areas under the receiver operating characteristic curve with a paired nonparametric approach. Multiple imputation was used for missing data. A clinically significant difference in areas under the receiver operating characteristic curve was defined as greater than or equal to 0.05, according to previous literature.

We included 19,408 patients, of whom 18% were tracheally intubated, 18% had brain injuries, 8% required neurosurgical intervention, and 6% died. The difference between the area under the receiver operating characteristic curve for the out-of-hospital GCS score and SMS was 0.05 (95% confidence interval [CI] −0.01 to 0.11) for emergency tracheal intubation, 0.05 (95% CI 0 to 0.09) for brain injury, 0.04 (95% CI −0.01 to 0.09) for neurosurgical intervention, 0.08 (95% CI 0.02 to 0.15) for mortality, and 0.05 (95% CI 0 to 0.10) for the composite outcome.

In this external validation, SMS was similar to the GCS score for predicting outcomes in traumatic brain injury in the out-of-hospital setting.