Minimal clinically important difference for pedometer step count in COPD: A prospective analysis

ABSTRACT

Background: Infection control precautions arising from the COVID-19 pandemic has led to challenges undertaking face-to-face exercise testing required for pulmonary rehabilitation (PR) exercise prescription and evaluation.1 Self-management programmes, incorporating physical activity, have been advocated as an alternative to PR when face-to-face assessment is not possible.1 Daily step count is the most commonly used physical activity outcome and does not require face-to-face assessment. We aimed to estimate the minimal clinically important difference (MCID) for daily pedometer step count in COPD, using response to PR as a model of improvement and longitudinal decline following PR as a model of deterioration. Methods: This was a secondary analysis of a trial that investigated the effectiveness of pedometer-directed step count targets in COPD as an adjunct to PR, with the study arms combined as the intervention did not result in significant between-group differences.2 We measured spirometry, Medical Research Council score, incremental shuttle walk test, Chronic Respiratory Questionnaire and pedometer step count (Yamax Digiwalker CW700) pre-, post- and six months following PR. Post-PR and six months post-PR, participants completed a Global Rating of Change Questionnaire 'How do you feel your physical activity levels have changed following rehabilitation?' and rated the response on a five-point Likert scale ( '1 I feel much more active' to '5 I feel much less active'). The MCID for improvement was defined as the median for '2 I feel a little more active' at the post-PR assessment. The MCID for deterioration was the median for '4 I feel a little less active' at the six-month assessment (compared to post-PR). Results: 152 participants enrolled in PR;80% and 70% attended the post-PR and six month assessments respectively. Baseline characteristics and change with PR and over time are (Table presented) in table 1. There were significant improvements in daily pedometer step count following PR and reductions at six months. The median (25th, 75th centile) MCID estimate for improvement and deterioration in daily pedometer step count was 427 (-443, 1286) and -456 (-2271, 650) steps respectively. Conclusion: The MCID estimates for improvement with PR and deterioration over time after PR are 427 and -456 steps respectively.