Validation of the Simplified Motor Score in the out-of-hospital setting for the prediction of outcomes after traumatic brain injury

Abstract

Study objective: 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.

Methods: 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.

Results: 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.

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