Testing the activity pacing questionnaire for validity, reliability and responsiveness: An outcome measure validation study

Abstract Activity pacing aims to manage symptoms of chronic pain and improve function by modifying pain-related behaviours: avoidance, overdoing and overdoing-underdoing cycling. Research regarding the effectiveness of activity pacing is unclear, and hindered by the absence of a validated scale. The previously developed 28-item Activity Pacing Questionnaire (APQ-28) comprises five domains: Activity adjustment, Activity planning, Activity consistency, Activity progression and Activity acceptance. This study aimed to shorten the APQ and provide evidence for its validity, reliability and responsiveness. Paper-based questionnaires collected data from patients with chronic pain attending healthcare services in England, UK, at baseline (n=347), and again at 2-weeks (n=130) and 12-weeks (n=121). Outcome measures included the APQ-28, and other measures of pacing, avoidance, overdoing, pain, self-efficacy, quality of life, physical/mental function, depression and anxiety. Statistical analyses explored validity, reliability, responsiveness and measurement error. Factor analysis (n=347) showed poor model fit for the previous five-factor model, leading to selecting a four-factor model (removing Activity acceptance) with three items per domain, forming the APQ-12 (CFI=0.995, TLI=0.992, RMSEA=0.052, SRMR=0.050). The four domains showed satisfactory internal consistency (Cronbach’s alpha=0.70–0.84) and test-retest reliability (n=130, ICC=0.53–0.64). Only Activity consistency showed significant responsiveness (n=121, Rho=0.27, 95% CI=0.1–0.43). Measurement error of the APQ-12 domains included smallest detectable change (range=1.55–1.76), standard error of measurement (range=0.56–0.63) and minimally important change (range=-0.17–0.33). Confirmatory factor analysis on external data supported the four-domain structure (CFI=0.983, TLI=0.977, RMSEA=0.071, SRMR=0.106). The APQ-12 shows promise as a multi-domain measure of activity pacing for use in clinical practice and future research.