Purpose: To compare societal values across health-state classification systems and to describe the performance of these systems at baseline in a large population of persons with confirmed diagnosis of intervertebral disc herniation (IDH), spinal stenosis (SpS), or degenerative spondylolisthesis (DS).
Methods: We compared values for EQ-5D (York weights), HUI (Mark 2 and 3), SF-6D, and the SF-36-derived estimate of the Quality of Well Being (eQWB) score using signed rank tests. We tested each instrument's ability to discriminate between health categories and level of symptom satisfaction. Correlations were assessed with Spearman rank correlations. We evaluated ceiling and floor effects by comparing the proportion at the highest and the lowest possible score for each tool. In addition, we compared proportions at the highest and lowest levels by dimension. The number of unique health states assigned was compared across instruments. We calculated the difference between those who were very dissatisfied and all others.
Results: Mean values ranged from 0.39 to 0.63 among 2097 participants ages 18-93 (mean age 53, 47% female) with significant differences in pair-wise comparisons noted for all systems. Correlations ranged from 0.30 to 0.78. Although all systems showed statistically significant differences in health state values when baseline comparisons were made between those who were very dissatisfied with their symptoms and those who were not, the magnitude of this difference ranged widely across systems. Mean differences (95% CI) between those very dissatisfied and all others were 0.30 (0.269, 0.329) for EQ-5D, 0.22 (0.190, 0.241) for HUI(3), 0.18 (0.161, 0.201) for HUI(2), 0.11 (0.095, 0.117) for SF-6D, 0.04 (0.039, 0.049) for eQWB, and 0.07 (0.056, 0.077) for VAS (with transformation applied to group means).
Conclusion: Differences in preference-weighted health state classification systems are evident at baseline in a population with confirmed IDH, SpS, and DS. Caution should be used when comparing health state values derived from various systems.