Minimum clinically important difference of the original and short-form Örebro musculoskeletal pain questionnaire for low back pain

Background

The Örebro Musculoskeletal Pain Questionnaire (Örebro), although originally designed as a screening tool, has become more prevalently used as an outcome measure in the literature. To our knowledge, no study has investigated the Örebro's performance as an outcome measure. The minimum clinically important difference (MCID) is a fundamental psychometric property of outcome measures.

Objectives

This study aimed to evaluate the performance of the Örebro (original and short-form versions) as an outcome measure, including establishing its MCID.

Methods

This was a secondary analysis of a randomised controlled trial. The study sample consisted of 300 low back pain patients, receiving physiotherapy. Patients completed the Örebro at 5 timepoints. To establish the MCID, an anchor-based method using receiver operating characteristic (ROC) curve analysis was utilised as our primary analysis method, supplemented with a distribution-based method deriving the standard error of measurement. Subpopulation analyses were carried out based on allocated treatment group and Örebro baseline score.

Results

Both questionnaires were capable of detecting change over time as all area under the curves (AUCs) were >0.7. The MCID was 20.3 for the Örebro and 9.0 for the SF-Örebro according to anchor-based methods. Using distribution-based methods, the MCID for the Örebro was 23.6 and 12.1 for the SF-Örebro. The MCID was larger for individuals with a higher baseline score but appeared independent of treatment group.

Conclusions

Both questionnaires were suitable for detecting change over time. To our knowledge, this is the first study to report a MCID estimation for either questionnaire.