Concurrent comparison of responsiveness in pain and functional status measurements used for patients with low back pain

Abstract

Study design: Prospective study of two samples of patients with acute and chronic low back pain, respectively.

Objectives: To compare the responsiveness of four functional status questionnaires, Roland Morris Disability Questionnaire (RMDQ), Oswestry Disability Index (ODI), Disability Rating Index (DRI), and Physical Functioning scale of the SF-36 (PFSF-36), and two pain scales, a Numerical Pain Rating Scale (NRS) and Visual Analogue Scale (VAS).

Summary of background data: Concurrent comparisons of different outcome measurements in back patients have been requested.

Methods: Norwegian versions of the scales and questionnaires were completed by 54 patients with acute (<3 weeks) and 50 patients with chronic low back pain (>3 months). Clinical change was estimated on a global change index. An alternative external criterion was the expected clinical course in the two cohorts. Mean changes, standardized response mean (SRM), and area under the receiver operating characteristic (ROC) curves with cutoff point for highest sensitivity and specificity were calculated.

Results: At the follow-up, 63% of the acute and 41% of the chronic sample reported improvement on the global change index. Large SRMs (1.3-2.0) and areas under the ROC curves (0.84-0.93) were found for the measurements in the acute sample. In the chronic sample, the SRMs (0.4-1.1) and areas under the ROC curves (0.65-0.83) were lower, in particular for the PFSF-36 and the VAS. There was no statistically significant difference between the responsiveness in the measurements, except for higher responsiveness in the NRS compared with the VAS when using expected clinical course as the external criterion for change.

Conclusion: The results suggest that all the outcome measures were appropriate for measuring changes in functional status and pain in patients with acute low back pain, whereas among chronic patients the RMDQ, ODI, DRI, and NRS were most appropriate.