To determine if the association of GCS with mortality is influenced by the presence of TBI.
Using the National Trauma Data Bank (2012; N = 639,549) we categorized patients as isolated TBI (12.8%), isolated non-TBI (33%), both (4.8%), or neither (49.4%) based on the presence of AIS codes of severity 3 or greater. We compared the ability GCS to discriminate survivors from non-survivors in TBI and in non-TBI patients using logistic models. We also estimated the odds ratios of death for TBI and non-TBI patients at each value of GCS using linear combinations of coefficients.
Death during hospital admission.
As the sole predictor in a logistic model GCS discriminated survivors from non-survivors at an acceptable level (c-statistic = 0.76), but discriminated better in the case of TBI patients (c-statistic = 0.81) than non-TBI patients (c-statistic = 0.70). In both unadjusted and covariate adjusted models TBI patients were about twice as likely to die as non-TBI patients with the same GCS for GCS values < 8; for GCS values > 8 TBI and non-TBI patients were at similar risk of dying.
A depressed GCS predicts death better in TBI patients than non-TBI patients, likely because in non-TBI patients a depressed GCS may simply be the result of entirely reversible intoxication by alcohol or drugs; in TBI patients, by contrast, a depressed GCS is more ominous because it is likely due to a head injury with its attendant threat to survival. Accounting for this observation into trauma mortality datasets and models may improve the accuracy of outcome prediction.