Defining the minimum level of detectable change for the Roland-Morris questionnaire

The Roland-Morris Questionnaire (RMQ) is a self-administered disability measure in which greater levels of disability are reflected by higher numbers on a 24-point scale. The RMQ has been shown to yield reliable measurements, which are valid for inferring the level of disability, and to be sensitive to change over time for groups of patients with low back pain. Little is known about the usefulness of this instrument in aiding decision making regarding individual patients. The purpose of this study was to determine the minimum level of detectable change when the RMQ is applied to individual patients.

The study sample consisted of 60 outpatients with low back pain.

The RMQ was administered at the subjects' initial visit and again 4 to 6 weeks later. Conditional standard errors of measurement (CSEMs) were computed for initial and follow-up RMQ scores, and these values were used to estimate the minimum level of detectable change. Results. Minimum levels of detectable change at the 90% confidence level varied from 4 to 5 RMQ points.

The magnitude of CSEMs is sufficiently small to detect change in patients with initial scores in the central portion of the scale (4-20 RMQ points); however, the magnitude is too large to detect improvement in patients with scores of less than 4 and deterioration in patients who have scores greater than 20.