Short communicationThe Edinburgh visual gait score – The minimal clinically important difference
Introduction
Baker et al. [1] developed the Gait Profile Score (GPS), a method of quantifying the kinematic output of 3D gait analysis, scoring the root-mean square difference from “normal” gait data, across the gait cycle. The GPS is a validated and an effective measure of gait quality which has been shown to be responsive to change after surgery [2]. The GPS has been demonstrated to correlate with experienced clinicians’ clinical judgement of gait abnormality [3], with the Gross Motor Function Classification System (GMFCS) and the Functional Assessment Questionnaire (FAQ) [4].
A minimal clinically important difference (MCID) is a quantifiable change in a scoring system that reflects a subjective assessment of clinical improvement. The originators of the GPS defined the MCID of 1.60 in their score, which was considered to be clinically meaningful to a patient [4].
The Edinburgh Visual Gait Score (EVGS) is a validated, robust and repeatable measure of gait quality in cerebral palsy [5], [6], [7], [8]. However, the numerical value of the MCID in the EVGS varies in the literature. The originators of the EVGS suggested that a change of three-units might be considered as indicating real change, based on the average intra-observer variability [5]. Gupta and Raja defined the MCID for the EVGS as 11 at six months and 15 at one year [9], based on the effect size of the post-surgical improvement in EVGS. A recent study defined the MCID as 4.2 points in the EVGS, based on the assessment of post-operative improvement in previous studies [10]. This variation in the MCID lends to uncertainty when interpreting the results of studies using EVGS as their outcome measure and to power future studies.
The EVGS has been shown to correlate with the GPS and the GMFCS [11]. Baker et al. [4] based their MCID on the FAQ [12] due to the wider spectrum of scoring, with a better representation of functional walking ability. To the authors’ knowledge, the MCID for the EVGS has not yet been calculated using independent variables.
The primary aim of this study was to calculate the MCID for the EVGS using correlations with the GMFCS and FAQ. The secondary aim was to confirm the numerical value of the MCID in the GPS. Given that the EVGS correlates closely with the GPS and both scores correlate with GMFCS level [11], the authors hypothesise that it will be possible to calculate an MCID for EVGS relative to GMFCS level and FAQ.
Section snippets
Methods
A consecutive series of 151 patients with diplegic cerebral palsy (GMFCS level I–III, mean age 13.3 years) were identified retrospectively from a database at the study centre. All had GMFCS, EVGS and GPS data and 141 of the 151 patients had FAQ data available.
GPS was calculated as an average of left and right lower limbs, for three separate trials, with one trial being defined as one complete walk. EVGS and GMFCS were evaluated by a senior gait analysis physiotherapist. The scores assigned to
Results
The mean scores for the 151 patients were 11.3 for EVGS (SD 4.61) and 12.3 for GPS (SD 3.94). Both the EVGS and GPS correlated with GMFCS level (R2 0.323 and 0.259 respectively, p < 0.001) (Fig. 1). The gradient of the regression line was 3.8 (95% confidence intervals (CI) 2.9–4.7) for EVGS and 2.9 (95% CI 2.1–3.7) for GPS. Age was included in the regression model to ensure no confounding effect, however, this was non-significant (p = 0.82) and was excluded. Both EVGS and GPS correlated with FAQ (R2
Discussion
This study has shown a significant correlation between EVGS and FAQ (p < 0.001). The correlation was a poor fit, as demonstrated by the low R-squared value but this likely reflects the highly variable data from patients with cerebral palsy. Despite this, given the significant correlation, linear regression calculated a 1.9-point change in EVGS corresponds to a one-point change in FAQ (95% CI 1.3–2.4). The authors propose an MCID of 2.4 for EVGS, based on the upper limit of the CI for the gradient
Conflicts of interest
None.
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