Manual wheelchair skills: objective testing versus subjective questionnaire

Abstract

Objectives: To test the hypothesis that the total scores of the Wheelchair Skills Test (WST) version 4.1, an observer-rated scale of wheelchair performance, and the Wheelchair Skills Test Questionnaire (WST-Q) version 4.1, a self-report of wheelchair skills, are highly correlated. We also anticipate that the WST-Q scores will be slightly higher, indicating an overestimation of capacity to perform wheelchair skills as compared with actual capacity.

Design: A cross-sectional, within-subjects comparison design.

Setting: Three Canadian cities.

Participants: Convenience sample of community-dwelling, experienced manual wheelchair users (N=89) ranging in age from 21 to 94 years.

Intervention: Not applicable.

Main outcome measures: Participants completed the subjective WST-Q version 4.1 followed by the objective WST version 4.1 in 1 testing session.

Results: The mean ± SD total percentage scores for WST and WST-Q were 79.5%±14.4% and 83.0%±12.1% for capacity and 99.4%±1.5% and 98.9%±2.5% for safety, respectively. The correlations between the WST and WST-Q scores were ρ=.89 (P=.000) for capacity and ρ=.12 (P=.251) for safety. WST-Q total score mean differences were an average of 3.5%±6.5% higher than WST scores for capacity (P=.000) and .52%±2.8% lower for safety (P=.343). For the 32 individual skills, the percentage agreement between the WST and WST-Q scores ranged from 82% to 100% for capacity and from 90% to 100% for safety.

Conclusion: WST and WST-Q version 4.1 capacity scores are highly correlated although the WST-Q scores are slightly higher. Decisions on which of these assessments to use can safely be based on the circumstances and objectives of the evaluation.

Copyright © 2012 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1. Bland-Altman Plot of the Mean Versus the Difference in WST and WST-Q 4.1 Capacity scores

This figure shows a comparison of the WST and WST-Q 4.1. The mean difference between the WST and WST-Q was 3.5 with an upper limit of agreement of 16.5 (mean difference + 2 standard deviations) and a lower limit of −9.5 (mean difference − 2 standard deviations). There were six outliers, so nearly 95% of the capacity differences fell between the 2 SD.

Figure 2. Bland-Altman Plot of the Mean Versus the Difference in WST and WST-Q 4.1 Safety scores

This figure shows a comparison of the WST and WST-Q 4.1. The mean difference between the WST and WST-Q was −0.5 with an upper limit of agreement of 5.1 (mean difference + 2 standard deviations) and a lower limit of −6.1 (mean difference − 2 standard deviations). Five outliers were identified for the safety scores, so 95% of the safety differences fell between 2 SD.

Figure 3. Total percentage scores for the WST and WST-Q 4.1 Capacity Scores

Note: All data points (n=89) are not visible due to 30 of the WST-Q and WST capacity scores being equal, resulting in many data points presenting as overlapping dots.