The lack of association between changes in functional outcomes and work retention in a chronic disabling occupational spinal disorder population: Implications for the minimum clinical important difference

Study Design. A prospective study in a chronic pain/disability population, relating changes in the Oswestry Disability Index (ODI), as well as the Mental Component Summary (MCS) and Physical Component Summary (PCS) of the Short Form-36 (SF-36), to work retention (WR) status at 1-year postrehabilitation. Objective. To explore the relationship between WR status and change in ODI, and the MCS and PCS of the SF-36, and determine if an MCID can be identified using WR as an external criterion for the group of patients under consideration. Summary Of Background Data. Clinically meaningful change may be defined through self-report, physician-based, or objective criteria of improvement, although most assessments have been based on self-report assessment of improvement. The disability occurring after work-related spinal disorders lends itself to anchoring self-report measures to objective work status outcomes 1-year post-treatment. Additional research is needed to evaluate the relationship between change and objective markers of improvement. Methods. A consecutive cohort of patients (n = 2024) with chronic disabling occupational spinal disorders completed an interdisciplinary functional restoration program, and underwent a structured clinical interview for objective, socioeconomic outcomes at 1-year post-treatment. The average percent change in the ODI, as well as the MCS and PCS of the SF-36, were calculated for patients who successfully retained work and those who had not after completing a functional restoration program. Predictive ability of the percent change scores were evaluated through logistic regression analysis. Results. No percent difference variables were strong predictors of WR status 1-year following treatment. Conclusion. The current analyses suggest that the ODI and SF-36 MCS and PCS measures are not responsive at the individual patient level when WR data are used as the external criterion using an anchor-based approach. This finding contrasts to reports of responsiveness based on distributional methods, or methods using self-report anchors of change.