Baseline health status and setting impacted minimal clinically important differences in COPD: an exploratory study

Abstract

Objectives: Minimal clinically important differences (MCIDs) are used as fixed numbers in the interpretation of clinical trials. Little is known about its dynamics. This study aims to explore the impact of baseline score, study setting, and patient characteristics on health status MCIDs in chronic obstructive pulmonary disease (COPD).

Study design and setting: Baseline and follow-up data on the COPD Assessment Test (CAT), Clinical COPD Questionnaire (CCQ), and St. George's Respiratory Questionnaire (SGRQ) were retrospectively analyzed from pulmonary rehabilitation (PR) and routine clinical practice (RCP). Anchor- and distribution-based MCID estimates were calculated and tested between settings, gender, age, Global initiative for Obstructive Lung Disease (GOLD) classification, comorbidities, and baseline health status.

Results: In total, 658 patients were included with 2,299 change score measurements. MCID estimates for improvement and deterioration ranged for all subgroups 0.50-6.30 (CAT), 0.10-0.84 (CCQ), and 0.33-12.86 (SGRQ). Larger MCID estimates for improvement and smaller ones for deterioration were noted in patients with worse baseline health status, females, elderly, GOLD I/II patients, and patients with less comorbidities. Estimates from PR were larger.

Conclusion: Baseline health status and setting affected MCID estimates of COPD health status questionnaires. Patterns were observed for gender, age, spirometry classification, and comorbidity levels. These outcomes would advocate the need for tailored MCIDs.

Keywords: COPD Assessment Test (CAT); Chronic obstructive pulmonary disease (COPD); Clinical COPD Questionnaire (CCQ); Health status; Minimal clinically important difference (MCID); St. George's Respiratory Questionnaire (SGRQ).