Minimal clinically important difference. Low back pain: outcome measures

Abstract

A proposed standard "core set" of outcome measures for low back pain includes 5 domains: back-specific function, generic health status, pain, work disability, and patient satisfaction. This paper focuses on the 2 recommended back-specific measures of function: the Roland-Morris Disability Questionnaire (RDQ) and the Oswestry Disability Index (ODI). We specifically address their ability to measure change. A systematic review of the literature identified a total of 78 and 71 (RDQ and ODI, respectively) articles as potentially relevant. Detailed tables are provided for each citation, with the type of back pain population studied, the type of change measured, the estimate of change, and the interval over which the change was studied. These tables should be used as a reference for sample size calculation. The responsiveness of the RDQ found in the literature ranges from 2 to 8 points on its 0 to 24 scale depending on what change is being measured. As a rough guide, Roland recommends that a change in 2-3 points on the RDQ should be considered the minimum clinically important change. Choosing any value larger than 5 in designing a clinical trial would risk underpowering the trial, since fewer patients are needed if a trial is designed on the basis of a large change score.