Minimal Clinically Important Differences for Patient-Reported Outcome Measures of Fatigue in Patients With COPD Following Pulmonary Rehabilitation

Abstract

Fatigue is a burdensome and prevailing symptom in patients with COPD. Pulmonary rehabilitation (PR) improves fatigue; however, interpreting when such improvement is clinically relevant is challenging. Minimal clinically important differences (MCIDs) for instruments assessing fatigue are warranted to better tailor PR and guide clinical decisions. This study estimated MCIDs for the Functional Assessment of Chronic Illness Therapy-Fatigue Subscale (FACIT-FS), the modified FACIT-FS, and the Checklist Individual Strength-Fatigue Subscale in patients with COPD following PR. Data from patients with COPD who completed a 12-week community-based PR program were used to compute the MCIDs. The pooled MCID was estimated by calculating the arithmetic weighted mean, resulting from the combination of anchor-based (weight, two-thirds) and distribution-based (weight, one-third) methods. Anchors were patients' and physiotherapists' Global Rating of Change Scale, COPD Assessment Test, St. George's Respiratory Questionnaire (SGRQ), and exacerbations. To estimate MCIDs, we used mean change, receiver-operating characteristic curves, and linear regression analysis for anchor-based approaches, and 0.5× SD, SE of measurement, 1.96× SE of measurement, and minimal detectable change for distribution-based approaches. Fifty-three patients with COPD (79%male, 68.4 ± 7.6 years of age, and FEV1 48.7 ± 17.4%predicted) were included in the analysis. Exacerbations and the SGRQ-impact and the SGRQ-total scores fulfilled the requirements to be used as anchors. Pooled MCIDs were 4.7 for FACIT-FS, 3.8 for the modified FACIT-FS, and 9.3 for the Checklist Individual Strength-Fatigue Subscale. The MCIDs proposed in this study can be used by different stakeholders to interpret PR effectiveness. ClinicalTrials.gov; No.: NCT03799666; URL: www.clinicaltrials.gov.