Research

Health status measurement in COPD: the minimal clinically important difference of the clinical COPD questionnaire

JWH Kocks¹ , MG Tuinenga¹ , SM Uil² , JWK van den Berg² , E Ståhl^3,4 and T van der Molen^1,4

¹Department of General Practice University Medical Center Groningen, The Netherlands

²Department of Pulmonary Diseases, Isala klinieken, Zwolle, The Netherlands

³AstraZeneca R&D, Lund, Sweden

⁴Primary Care Respiratory Medicine, University of Aberdeen, UK

author email corresponding author email

Respiratory Research 2006, 7:62doi:10.1186/1465-9921-7-62

Published:	7 April 2006

Abstract

Background

Patient-reported outcomes (PRO) questionnaires are being increasingly used in COPD clinical studies. The challenge facing investigators is to determine what change is significant, ie what is the minimal clinically important difference (MCID). This study aimed to identify the MCID for the clinical COPD questionnaire (CCQ) in terms of patient referencing, criterion referencing, and by the standard error of measurement (SEM).

Methods

Patients were ≥40 years of age, diagnosed with COPD, had a smoking history of >10 pack-years, and were participating in a randomized, controlled clinical trial comparing intravenous and oral prednisolone in patients admitted with an acute exacerbation of COPD. The CCQ was completed on Days 1–7 and 42. A Global Rating of Change (GRC) assessment was taken to establish the MCID by patient referencing. For criterion referencing, health events during a period of 1 year after Day 42 were included in this analysis.

Results

210 patients were recruited, 168 completed the CCQ questionnaire on Day42. The MCID of the CCQ total score, as indicated by patient referencing in terms of the GRC, was 0.44. The MCID of the CCQ in terms of criterion referencing for the major outcomes was 0.39, and calculation of the SEM resulted in a value of 0.21.

Conclusion

This investigation, which is the first to determine the MCID of a PRO questionnaire via more than one approach, indicates that the MCID of the CCQ total score is 0.4.