Glasgow Coma Scale score, mortality, and functional outcome in head-injured patients

Preresuscitation Glasgow Coma Scale (P-GCS) score is frequently obtained in injured patients and incorporated into mortality prediction. Data on functional outcome in head injury is sparse. A large group of patients with head injuries was analyzed to assess relationships between P-GCS score, mortality, and functional outcome as measured by the Functional Independence Measure (FIM).

Records for patients with International Classification of Diseases, Ninth Revision diagnosis codes indicating head injury in a statewide trauma registry between 1994 and 2002 were selected. P-GCS score, mortality, and FIM score at hospital discharge were integrated and analyzed.

Of 138,750 patients, 22,924 patients were used for the mortality study and 7,150 patients for the FIM study. A good correlation exists between P-GCS score and FIM, as determined by rank correlation coefficients, whereas mortality falls steeply between a P-GCS score of 3 and a P-GCS score of 7 followed by a shallow fall. Although P-GCS score is related to mortality in head-injured patients, its relationship is nonlinear, which casts doubt on its use as a continuous measure or an equivalent set of categorical measures incorporated into outcome prediction models. The average FIM scores indicate substantial likelihood of good outcomes in survivors with low P-GCS scores, further complicating the use of the P-GCS score in the prediction of poor outcome at the time of initial patient evaluation.

Although the P-GCS score is related to functional outcome as measured by the FIM score and mortality in head injury, current mortality prediction models may need to be modified to account for the nonlinear relationship between P-GCS score and mortality. The P-GCS score is not a good clinical tool for outcome prediction in individual head-injured patients, given the variability in mortality rates and functional outcomes at all scores.