Investigating the MCID of health status tools for patients with COPD in pulmonary rehabilitation

Background: COPD is a major public health problem. Health status has become an important tool in its diagnostics and management with CCQ, CAT and SGRQ as the main instruments. Important is to what extent a change in its score is clinically relevant. The Minimal Clinically Important Difference (MCID) defines this. Current MCIDs are 0.4 (CCQ), 2.0 (CAT) and 4.0 (SGRQ). This study investigated the MCID of these tools using multiple approaches, since existing evidence is limited. Methods: In total 316 patients participated in a 3-week Pulmonary Rehabilitation programme (63% male, 51%FEV 1 pred., 41 mean packyears, 58 years mean age, 2/50/38/10% GOLD stage I/II/III/IV). Anchor-based approaches, including patient-referencing, criterion-referencing and questionnaire-referencing, and the distribution-based methods SEM and 0.5SD were used to determine the MCID. Results: Discussion: This study showed that the MCID of a tool might differ depending on which method is used. Estimates ranged from 0.30 to 0.51 for CCQ, from 2.17 to 3.50 for CAT and from 6.17 to 7.92 for SGRQ. The current published MCID of the CCQ fits well in this range, however the MCID of the CAT and SGRQ in the literature is below the range found.