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.

Abstract

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. 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. 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. 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. No percent difference variables were strong predictors of WR status 1-year following treatment. 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.