Introduction: An ability to assess longitudinal changes in health status is crucial for the outcome measures used in treatment efficacy trials. The aim of this study was to verify the responsiveness of the Italian versions of the Oswestry Disability Index (ODI) and the Roland Morris Disability Questionnaire (RMDQ) in subjects with subacute or chronic low back pain (LBP).
Material and methods: At the beginning and end of an 8 week rehabilitation programme, 179 patients completed a booklet containing the ODI, the RMDQ, a 0-10 numerical rating scale (NRS), and the 36-item Short-Form Health Survey (SF-36). A global perception of change scale was also completed at the end of the programme, and collapsed to produce a dichotomous outcome (i.e. improved vs. not improved). Responsiveness was assessed by means of distribution methods [minimum detectable change (MDC); effect size (ES); standardised response mean (SRM)] and anchor-based methods (ROC curves).
Results: The MDC for the ODI and RMDQ was, respectively, 13.67 and 4.87; the ES was 0.53 and 0.68; and the SRM was 0.80 and 0.81. ROC analysis revealed an area under the curve of 0.71 for the ODI and 0.64 for the RMDQ, thus indicating discriminating capacity; the best cut-off point for the dichotomous outcome was 9.5 for the ODI (sensitivity 76% and specificity 63%) and 2.5 for the RMDQ (sensitivity 62% and specificity 55%). These estimates were comparable between the subacute and chronic subjects. Both the ODI and the RMDQ moderately correlated with the SF-36 and NRS (Spearman's and Pearson's correlation coefficients of >0.30).
Conclusion: The Italian ODI and RMDQ proved to be sensitive in detecting clinical changes after conservative treatment for subacute and chronic LBP. Our findings are consistent with those published in the literature, thus allowing cross-cultural comparisons and stimulating cross-national studies.