Psychometric evaluation of the leg activity measure (LegA) for outcome measurement in people with brain injury and spasticity

Abstract

Purpose The aim of this study is to evaluate the properties of the Leg Activity measure according to COnsensus‐based Standards for the selection of health Measurement INstruments. Method Participants were assessed at baseline, one day, 6 weeks and 12 weeks, following treatment for leg spasticity with botulinum toxin and physical interventions. Results In stage 1, 64 participants were recruited to evaluate the initial psychometric properties of Leg Activity measure. In stage 2, 100 additional participants were recruited, to evaluate the scaling properties. Total sample of 164 participants was used. Construct validity was supported for “passive function”, “active function” and “impact on quality of life”. Cronbach’s alpha was 0.86, 0.97 and 0.87 respectively for the scales. Item level test-retest agreement ranged from 91–97% (Kappa 0.75–0.95). Following treatment for spasticity (n = 64), the Leg Activity measure “passive function” and “impact on life” scales were responsive to change. Principal components analysis confirmed the constructs and a unidimensional Rasch Partial Credit Model was subsequently established for each scale. Transformation to an interval scale was achieved. Using the ordinal-to-interval conversion tables, parametric statistical analysis may be used. Conclusion The study provides support for the Leg Activity measure being valid, reliable and responsive. Implications for rehabilitation The Leg Activity measure is the only published self-report measure in the current literature that addresses passive and active function as well as impact on quality of life, of the paretic leg in a comprehensive manner. The initial evaluation of Leg Activity measure psychometric properties, in relation to the COnsensus‐based Standards for the selection of health Measurement INstruments checklist and Medical Outcomes Trust Quality Criteria, supports its measurement properties for clinical and research use. The Leg Activity measure as a valid, reliable and responsive tool for the evaluation of treatment in leg spasticity including condition specific (spasticity) quality-of-life.