DOES MODIFICATION OF THE INNSBRUCK AND THE GLASGOW COMA SCALES IMPROVE THEIR ABILITY TO PREDICT FUNCTIONAL OUTCOME

Background: The accurate prediction of functional outcome requires the development of multivariate models. To enhance their contribution to such models, the predictive power of each component must be optimized. Objectives: To improve the predictive power of coma scales as the fir st step in building more sophisticated multivariate models to predict specific levels of functional outcome. Design: Prospective descriptive study. Setting: Neurology and neurosurgery intensive care unit (NNICU ) in a tertiary care academic center. Patients: Eighty-four patients w ith acute traumatic brain injury, intracerebral hemorrhage, subarachno id hemorrhage, or ischemic stroke. Interventions: None. Main Outcome M easures: The Glasgow Coma Scale (GCS) and Innsbruck Coma Scale (ICS) w ere administered within 24 hours of admission to the NNICU and then at 48-hour intervals until discharge of the patient from the NNICU. The assessments were performed by 3 occupational therapy graduate students working under the supervision of the medical director of the NNICU. T he functional outcome at 3 months after discharge from the hospital wa s assessed by telephone by the same nurse using the following categori es: (1) dead, (2) receiving nursing home or custodial care, (3) home w ith help, or (4) independent. Cronbach's alpha estimates of reliabilit y for each scale were computed using all scores obtained during the st udy. The analyses indicated that the verbal response item of the GCS a nd the oral automatisms item of the ICS were less reliable in this pat ient population. The scales were modified by deleting those items, and predictive validity for the original and modified scales was computed using a discriminant function of the admission scores. Results: Befor e modification, both scales were best at predicting independence (GCS and ICS, 71% correct) and mortality (GCS, 60% correct, ICS, 56% correc t). The modifications produced a modest improvement in the ability of both scales to better predict levels of outcome (modified GCS: home wi th help, 33% correct, independent, 71% correct; modified ICS: home wit h help, 0% correct, independent, 74% correct). Conclusions: By deletin g items with low reliability from the ICS and the GCS we achieved impr oved reliability and predictive validity. The improvement in predictiv e power, however, was inadequate to accurately predict functional outc ome. Combining clinical scales with other demographic, physiological, functional, and radiographic data will be needed to achieve useful pre dictions of functional outcome.