Background: Linking patient-reported back pain outcomes with health utility measures is valuable for informing economic evaluations.
Methods: We used the Back pain Outcomes using Longitudinal Data (BOLD) registry to assess back pain and quality-of-life measures. The BOLD registry includes participants ≥65 years from 3 health systems. We used multiple baseline outcome measures: Roland-Morris Disability Questionnaire (RMDQ), Euroqol-5D (EQ-5D), and back and leg pain numerical rating scales (NRS). To develop and validate a model, we used a standard split-sample method and a novel multisite validation approach. We applied linear regression to map RMDQ to EQ-5D, adjusting for age, sex, pain numerical rating scores, and nonlinear transformations of outcome measures. We computed R (2), root mean squared error, and mean absolute error (MAE) for purposes of model selection. The final model included EQ-5D as the dependent variable with independent variables of age, RMDQ, and back NRS. We used this model to predict EQ-5D scores in validation samples.
Results: In total, 5224 participants had both baseline RMDQ and EQ-5D. Mean age was 74 years (65% female). Negative correlations (-0.72) were observed at baseline for RMDQ and EQ-5D. The selected model from all developmental samples had R (2) >0.41 and MAE < 0.119. Validation analyses indicated no differences in estimated v. observed mean EQ-5D scores in the split sample. Validation using the multisite validation approach identified prediction error variability, MAE of 0.081 to 0.119, when predicting EQ-5D.
Limitations: The statistical relationship may not generalize well to all study populations as we demonstrated in our multisite analysis.
Conclusions: An empirical algorithm predicting EQ-5D weights from RMDQ scores provides a currently unavailable link for conducting economic evaluations in low back pain studies.
Keywords: EQ-5D; Roland-Morris Disability Questionnaire; health economic evaluations; low back pain; older adults.
© The Author(s) 2014.