Evaluation of the meaningfulness of health-related quality of life improvements as assessed by the SF-36 and the EQ-5D VAS in patients with active Crohn's disease

Crohn's disease (CD) is a chronic inflammatory illness characterized by episodic abdominal pain, diarrhoea, fever, bleeding and obstruction. While the Crohn's Disease Activity Index (CDAI) remains the most commonly accepted measure for assessing the disease status in clinical trials, patient-reported outcome (PRO) instruments are being utilized more frequently to provide information about health-related quality of life (HRQOL). To facilitate interpretation of results, it is common to identify a meaningful unit of PRO score change, such as a minimal clinically important difference (MCID). To define and apply MCID estimates for the SF-36 and EuroQol-5D visual analogue scale (EQ-5D VAS) for use in CD treatment evaluation. Data from two phase III randomized controlled trials of certolizumab pegol were utilized. MCID estimates were computed from one trial using anchor-based and distribution-based methods. These estimates were applied to data from the other trial. SF-36 PCS and MCS MCID estimates ranged from 1.6 to 7.0 and 2.3 to 8.7 respectively, depending on approach. EQ-5D VAS MCID estimates ranged from 4.2 to 14.8. For the first time, the MCID values provided interpretation guidelines for PRO results in CD. This research demonstrates that patients treated with certolizumab pegol benefit from meaningful and sustained HRQOL improvements.