Abstract
To the Editor:
Bodien and colleagues 1 note that the Glasgow Coma Scale (GCS) is the most widely used behavioral measure for assessment of acute head injury severity. We welcome the support they express for reporting the findings separately for its three component subscales. In contrast, their portrayal of supposed limitations of the aggregate Coma Score is flawed and based on criticisms for not doing something it was never intended to do.
The aim in the introduction of the GCS for monitoring patients in the acute stage after brain injury was to break away from the practice of assigning labels to supposedly different states in the continuum of altered consciousness. 2 Despite this, the authors assessed the GCS by mapping all combinations of GCS subscores obtained clinically against paper criteria for diagnosing several states within the spectrum of disorders of consciousness (DoC). With the exception of the persistent vegetative state, to which the GCS was not intended to apply, none of these were described until many years after the Coma score and scale were introduced. Bodien and colleagues state that more than one DoC diagnosis was possible for the same GCS total score. However, no information was given about the interplay between combinations of GCS subscale scores, and the occurrence of overlaps. The occurrence of overlaps, or conversely gaps, could have been a reflection of variable clinical manifestations in the same diagnostic group, and not all combinations of GCS subscale scores are clinically possible.
The authors state that GCS “administration and scoring is not standardized,” whereas (as later acknowledged) detailed, definitive practical guidance is freely available at the GCS website, which receives >20,000 visits/month. 3 A systematic review identified 52 studies on GCS reliability, which makes it one of the most studied clinical scales. 4 In contrast, information about the reliability of assessment of DoC is considerably more limited.
The wealth of information relating GCS score to findings in the acute phase and to late outcome after head injury is widely acknowledged. Supposed limitations of the Scale, such as its prognostic validity being “insufficient for predicting outcome in individual patients,” reflect entirely unrealistic expectations. No single feature alone can reliably predict late outcome in individuals or groups and multi-variable modeling is required. 5 Recently we demonstrated that pupil reactivity, patient age, and CT scan findings, in combination with GCS, can provide useful predictions of patient functional outcome and mortality at 6 months. 6
There is a need for valid and reliable tools that might compliment the GCS in assessing responsiveness during and after acute care. Bodien and colleagues acknowledge that specialized skills and observation over time are required to differentiate certain of the disorders of consciousness and that these are not found in the turmoil of acute care. The authors suggest a short version of the Coma Recovery Scale-Revised, but the validity and reliability of this are unknown. Variability in responsiveness is an issue in people with DoC where responses are often transient, inconsistent, or absent. The practical utility of these approaches in acute care therefore remains to be seen.