Responsiveness of the EQ-5D health-related quality-of-life instrument in assessing low back pain.

OBJECTIVE

To compare the responsiveness of the EuroQol five-dimensional questionnaire (EQ-5D) generic quality-of-life instrument with that of specific instruments-the Brief Pain Inventory (BPI) and the Oswestry Disability Index (ODI)-in assessing low back pain.

METHODS

Data were obtained from a group of patients receiving epidural steroid injections. We assessed responsiveness by using correlation, by estimating standardized response means, by receiver operating characteristic curve analysis, and by comparing the minimum clinically important differences peculiar to each of the instruments.

RESULTS

ODI, BPI, and EQ-5D index scores, and changes in scores, were found to be correlated. Estimated standardized response means and receiver operating characteristic curve analysis suggested lower responsiveness for the EQ-5D index score. Clinically significant categories of mild, moderate, and severe BPI pain intensity translated into progressively and significantly lower mean EQ-5D index scores. An increase or a decrease in severity level reported on any of the five EQ-5D dimensions was associated with significant changes (with appropriate signs) in the condition-specific scores. No change in severity in any EQ-5D dimension was associated with no change in the specific scores. Significant changes in the EQ-5D index scores were associated with clinically important changes in the ODI and BPI scores. Correlation between index scores and responses on EQ-5D's visual analogue scale was only moderate.

CONCLUSIONS

The EQ-5D index is less responsive than instruments specific to pain measurement, although it is capable of indicating clinically important changes. The lower responsiveness arises from EQ-5D's more limited gradation of severity and its multidimensionality.