THE CONUNDRUM OF THE GLASGOW COMA SCALE IN INTUBATED PATIENTS - A LINEAR-REGRESSION PREDICTION OF THE GLASGOW VERBAL SCORE FROM THE GLASGOWEYE AND MOTOR SCORES

Background: The Glasgow Coma Scale (GCS), which is the foundation of t he Trauma Score, Trauma and Injury Severity Score, and the Acute Physi ology and Chronic Health Evaluation scoring systems, requires a verbal response. In some series, up to 50% of injured patients must be exclu ded from analysis because of lack of a verbal component for the GCS. T he present study extends previous work evaluating derivation of the ve rbal score from the eye and motor components of the GCS. Methods: Data were obtained from a state trauma registry for 24,565 unintubated pat ients. The eye and motor scores were used in a previously published re gression model to predict the verbal score: Derived Verbal Score = -0. 3756 + Motor Score (0.5713) + Eye Score * (0.4233). The correlation of the actual and derived verbal and GCS scales were assessed. In addi tion the ability of the actual and derived GCS to predict patient surv ival in a logistic regression model were analyzed using the PC SAS sys tem for statistical analysis. The predictive power of the actual and t he predicted GCS were compared using the area under the receiver opera tor characteristic curve and Hosmer-Lemeshow goodness-of-fit testing. Results: A total of 24,085 patients were available for analysis. The m ean actual verbal score was 4.4 +/- 1.3 versus a predicted verbal scor e of 4.3 +/- 1.2 (r = 0.90, p = 0.0001). The actual GCS was 13.6 +/- 3 .5 versus a predicted GCS of 13.7 +/- 3.4 (r = 0.97, p = 0.0001). The results of the comparison of the prediction of survival in patients ba sed on the actual GCS and the derived GCS shaw that the mean actual GC S was 13.5 + 3.5 versus 13.7 + 3.4 in the regression predicted model. The area under the receiver operator characteristic curve for predicti ng survival of the two values was similar at 0.868 for the actual GCS compared with 0.850 for the predicted GCS. Conclusions: The previously derived method of calculating the verbal score from the eye and motor scores is an excellent predictor of the actual verbal score. Furtherm ore, the derived GCS performed better than the actual GCS by several m easures. The present study confirms previous work that a very accurate GCS can be derived in the absence of the verbal component.