Preference-based quality of life measurement in patients with cervical spondylotic myelopathy

Study Design. Prospective cross-sectional observational cohort study. Objectives. To assess the performance of preference-based quality of life (QOL) instruments in patients with cervical spondylotic myelopathy (CSM). Summary of Background Data. Generic health status instruments (e.g., SF-36) or disease-specific health status measures (e.g., myelopathy scales) are typically used to measure QOL in patients with CSM; however, these instruments only examine a limited number of domains that contribute to QOL. An alternative is preference-based QOL methods, which integrate all factors contributing to QOL and provide a comprehensive individualized measure of how patients value their current health state. Methods. We used four preference-based QOL methods to measure QOL in a cohort of 79 patients with CSM: 1) visual analogue scale, 2) standard gamble, 3) time trade-off, and 4) willingness to pay. We measured health status with the SF-36 and with CSM disease-specific scales devised by Nurick, Harsh, Cooper, and the Japanese Orthopedic Association. We used multivariate linear regression techniques to examine the relationships between preference-based QOL, generic health status, CSM disease-specific health status, and patient characteristics. Results. Median preference-based QOL measurements for the CSM cohort were as follows: visual analogue scale, 0.50; standard gamble, 0.79; time trade-off, 0.75, and willingness to pay, $38,256. Preference-based QOL was not well explained by generic health status, CSM disease-specific health status, or patient characteristics, as shown by regression models that were unable to account more than 21% of the variation in preference-based QOL (R ² ≤ 0.21). Conclusions. Preference-based QOL in patients with CSM is poorly correlated with generic health status, CSM disease-specific health status, or patient characteristics. Studies of CSM and other spine diseases should consider incorporating preference-based QOL measures for a fuller evaluation of the impact of spine disease and its treatment on QOL.