Glasgow Coma Scale (GCS)

Overview

We conducted a literature search to identify all relevant publications on the psychometric properties of the GCS in individuals with stroke. We identified only three studies specifically examining the GCS in stroke (Weir et al., 2003; Prasad & Menon, 1998; Weingarten, Bolus, Riedinger, Maldonado, Stein, & Ellrodt, 1990). Thus, in this review we will present psychometric data from studies examining neurological patients that include patients with stroke.

Floor/Ceiling Effects

Not reported.

Reliability

Internal consistency:
Mayer, Dennis, Peery, Fitsimmons, Du, Bernardini, Commichau, et al. (2003) examined the internal consistency of the GCS in 171 patients in the neurointensive care unit. Cronbach’s alpha was found to be excellent (alpha = 0.83).

Test-retest:
Not reported.

Inter-rater:
Gill, Reiley, and Green (2004) examined the inter-rater reliability of the GCS in 116 emergency department patients with various diagnoses (10 clients with stroke, 9% of the sample). Two attending emergency physicians independently assessed the GCS within 5 minutes of each other while blinded to each other’s scores. Kappa statistics were calculated for each of the GCS subtests and the total score. Best eye response had adequate inter-rater reliability (weighted k = 0.72) as did Best verbal response (weighted k = 0.48) and Best motor response (weighted k = 0.40). The agreement percentage for total GCS was 32% (Kendall’s T-b = 0.74; Spearman rho = 0.86; Spearman rho2 = 75%). Agreement percentage for GCS Best eye response was 74% (T-b = 0.72; Spearman rho = 0.76; Spearman rho2 = 57%), verbal 55% (T-b = 0.59; Spearman rho = 0.67; Spearman rho2 = 44%), and motor 72% (T-b = 0.74; Spearman rho = 0.81; Spearman rho2 = 65%).

Mayer et al. (2003) examined the inter-rater reliability of the CGS in 64 patients in the neurointensive care unit. The GCS was administered by 2 or 3 examiners within 5 to 10 minutes of each other. Examiners were blinded to each other’s scores. Inter-rater reliability was excellent for the total GCS (weighted k = 0.91), Best visual response (weighted k = 0.86), Best motor response (weighted k = 0.91) and Best verbal response (weighted kappa = 0.76).

Validity

Content:
Not available.

Criterion:
Concurrent:
No gold standard exists against which to compare the GCS.

Predictive:
Weingarten et al. (1990) examined whether the GCS was as accurate in predicting stroke mortality as APACHE II (Knaus, Draper, Wagner, & Zimmerman, 1985), a scale that consists of the GCS score plus 11 other physiological variables, age, and a chronic health evaluation. 246 patients hospitalized with stroke, including 49 oversampled mortalities were included in the study. The GCS was found to adequately predict stroke mortality, and was found to be as accurate as the APACHE II score in predicting stroke mortality with the oversampled mortalities (r = -0.50 and r = 0.50, respectively) and after excluding the oversampled mortalities (r = -0.40 and r = 0.39, respectively).

Prasad and Menon (1998) compared the predictive accuracy of three alternative strategies for verbal scoring in 275 patients with acute stroke who were either intubated or had dysphasia. The total GCS score predicted acute mortality with 87% accuracy using just the Best eye response and Best motor response subscales, versus 88% accuracy with all three subscales. Thus, the authors concluded that the verbal subscale could be excluded from the total GCS score without loss of predictive value in clients with stroke.

Weir, Bradford, and Lees (2002) examined the ability of the GCS to predict 2-week mortality and 3-month recovery (survival, living at home) in a large cohort of individuals with acute stroke. The results of 1217 patients with stroke (including 349 patients with dysphagia) were analyzed. Area under the receiver operating curve (AUC) was used by the authors to compare versions of the GCS. The results of the AUC calculations indicated that the total GCS score had a greater AUC than the GCS without the verbal score for predicting 2-week mortality. This was apparent for all participants together (AUC = 0.78 for the total GCS score; 0.76 for the GCS without the verbal score) and for only the participants with dysphasia (AUC = 0.72 for total GCS score; 0.71 for the GCS without the verbal score). Similarly, the total GCS score was also better than the GCS without the verbal score for predicting 3-month recovery in all participants (AUC = 0.71 for the total GCS score; 0.67 for the GCS without the verbal score) and in participants with dysphasia only (AUC = 0.74 for the total GCS score; 0.70 for the GCS without the verbal score). These results suggest that in contrast to the findings by Prasad and Menon (1998), the verbal subscale should not be excluded in clients with dysphasia since it adds important prognostic information. These results also suggest that the total GCS score can predict early mortality and 3-month recovery and that the GCS better predicted the outcome of early mortality than the outcome of 3-month recovery.

Construct :
Convergent/Discriminant :
Mayer et al. (2003) examined the convergent validity of the GCS with the 60-Second Test (SST) in 171 patients in the neurointensive care unit using Spearman’s rho. The GCS and SST had an excellent correlation (Spearman’s rho = 0.72).

Known groups:
Not examined.

Responsiveness

Mayer et al. (2003) examined the responsiveness of the GCS in 36 patients in the neurointensive care unit. Patients underwent a baseline testing, followed by 1-13 follow-up encounters performed every 12-24 hours. The neurologist performed a brief standardized examination and provided a global clinical impression of change in level of consciousness (better, the same, or worse) compared with the prior encounter. According to the global impression of a neurologist, patients improved in 24% and worsened in 26% of the 187 follow-up examinations. Sensitivity of the GCS to these changes in level of consciousness was poor (46%).

References
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