Baseline dependent minimally important differences for clinical outcomes of pulmonary rehabilitation in people with COPD

• Published in: Pulmonology 2024-01, Vol.30 (1), p.24-33
• Main Authors: Jenkins, A.R., Groenen, M.T.J., Vaes, A.W., Janssen, D.J.A., Wouters, E.F.M., Franssen, F.M.E., Spruit, M.A.
• Format: Article
• Language: English
• Subjects: Aged; Clinical outcomes; Female; Humans; Male; Middle Aged; Minimally important differences; Pulmonary Disease, Chronic Obstructive; Pulmonary rehabilitation; Respiratory Function Tests; Surveys and Questionnaires; Walk Test
• ISSN: 2531-0437; 2531-0437
• DOI: 10.1016/j.pulmoe.2023.06.004

Minimally important differences (MIDs) for common outcomes of pulmonary rehabilitation are well documented for people with chronic obstructive pulmonary disease (COPD). It is not known whether MIDs differ based on COPD disease characteristics. This study aimed to estimate MIDs for clinical outcomes of pulmonary rehabilitation dependent upon baseline characteristics. A database containing 2791 people with COPD was split into derivation (n=2245; age 66±9 years; 50% males; FEV1 47±20% predicted) and comparator (n=546; age 66±9 years; 47% males; FEV1 46±21% predicted) cohorts. MIDs were estimated using 0.5 x SD (symmetrically distributed) or 0.5 x IQR (non-symmetrically distributed) for: 6-minute walk test (6MWT), constant work rate test (CWRT), COPD assessment test (CAT), St. George's respiratory questionnaire (SGRQ), hospital anxiety and depression scale (HADS), and fat-free mass index (FFMI). MIDs were estimated based on baseline outcome scores, lung function, modified medical research council (mMRC) grade and FFMI. MID estimates were comparable to previously reported values. MIDs for SGRQ domains (Symptom=8.7 points, Activity=7.1 points, Impact=8.1 points) and FFMI were produced (0.36kg/m2). There was greater variation of change in 6MWT, SGRQ-activity, SGRQ-impact, HADS and FFMI on which the MIDs were determined when categorising for baseline values (all, p