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Published on: June 10, 2013
Visual Analogue Scale has higher assay sensitivity than WOMAC pain in detecting between-group differences in
Bruno R da Costa1, Pakeezah Saadat2, Reto Basciani3
1Applied Health Research Centre (AHRC), Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, ON, Canada; Institute of Primary Health Care (BIHAM), University of Bern, Bern, Switzerland; Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada.
Objective:
To compare assay sensitivity of the Visual Analogue Scale (VAS) for global osteoarthritis pain and the Western Ontario and McMaster University (WOMAC) pain subscale, and the associated between-trial heterogeneity in effect sizes (ES).
Design:
We included trials with placebo, sham or non-intervention control that included at least 100 patients with hip or knee osteoarthritis per arm, reporting both VAS and WOMAC pain scores. ES were calculated as between-group difference in means divided by the pooled standard deviation and compared using a paired t-test. ES and τ2 as a measure of between-trial heterogeneity were combined using random-effects meta-regression with robust variance estimation to account for the correlation of data within trials and meta-analyses.
Results:
Twenty-eight trials with 44 randomized comparisons were included. In 28 comparisons (64%), ES from VAS favoured the intervention more than those from WOMAC pain (P = 0.003). Twenty-six p-values (59%) were smaller according to VAS (P = 0.008). The 44 comparisons contributed to 12 meta-analyses. Eleven meta-analyses (92%) showed larger benefits of interventions according to VAS, with a combined overall difference in ES of -0.08 (95% CI -0.14 to -0.02). τ2 was similar for VAS and WOMAC pain (difference in τ2, -0.003, 95% CI -0.009 to 0.004).
Conclusion:
The VAS for global pain had slightly higher assay sensitivity at trial and meta-analysis levels than the WOMAC pain subscale without relevant increase in between-trial heterogeneity.
