A comparison of the prehospital motor component of the glasgow coma scale (mGCS) to the prehospital total GCS (tGCS) as a prehospital risk adjustment measure for trauma patients

Objective. This study compared the prehospital motor component subscale of the Glasgow Coma Scale (mGCS) to the prehospital total GCS (tGCS) score for its ability to predict the need for intubation, survival to hospital discharge, and neurosurgical intervention in trauma patients. Methods. This is a retrospective analysis of an urban level 1 trauma registry. All trauma patients presenting to the trauma center emergency department via emergency medical services from July 2008 through June 2010 were included. The area under the receiver operating characteristics curve (AUC) analysis was used to compare the predictive ability of the prehospital mGCS to tGCS for three outcomes: intubation, survival to hospital discharge, and neurosurgical intervention. Two subgroups (patients with injury severity score [ISS] ≥ 16 and traumatic brain injury [TBI] [head abbreviated injury score (AIS) ≥ 3]) were analyzed. An a priori statistically significant absolute difference of 0.050 in AUC between mGCS and tGCS for these clinical outcomes was used as a clinically significant difference. Multiple imputation was used for missing prehospital GCS data. Results. There were 9,816 patients, of which 4% were intubated, 3.8% had neurosurgical intervention, and 97.1% survived to hospital discharge. The absolute difference in AUC (prehospital tGCS minus mGCS) for all cases was statistically significant for all three outcomes but did not reach the clinical significance threshold: survival = 0.010 (95% CI: 0.002-0.018), intubation = 0.018 (95% CI: 0.011-0.024), and neurosurgical intervention = 0.019 (95% CI: 0.007-0.029). The difference in AUC between tGCS and mGCS for the subgroups ISS ≥ 16 (n = 1,151) and TBI (n = 1,165) did not reach clinical significance for the three outcomes. The discriminatory ability of the prehospital mGCS was good for survival (AUC: all patients = 0.89, ISS ≥ 16 = 0.84, traumatic brain injury = 0.86) excellent for intubation (AUC: all patients = 0.95, ISS ≥ 16 = 0.91, traumatic brain injury = 0.91), and poor for neurosurgical intervention (AUC: all patients = 0.67, ISS ≥ 16 = 0.57, traumatic brain injury = 0.60). Conclusion. The prehospital mGCS appears have good discriminatory power and is equivalent to the prehospital tGCS for predicting intubation and survival to hospital discharge in this trauma population as a whole, those with ISS ≥ 16, or TBI.