A proposed definition of remission from chronic pain, based on retrospective evaluation of 24-month outcomes with spinal cord stimulation

Objective: In the treatment of chronic diseases, remission is commonly used as a meaningful treatment goal, synonymous with the absence of significant clinical signs and symptoms of a disease, but not representing a cure. The objective of this paper is to propose a definition for remission for use as an outcome to evaluate the long-term efficacy of therapies for chronic pain. Methods: Data from a randomized clinical trial (NCT01609972) testing the efficacy of spinal cord stimulation in low back and leg pain subjects was used to evaluate the association between pain and functional outcomes and identify the cut-off value to predict remission. Available data over 24-month assessment period included visual analog score (VAS), disability (Oswestry Disability Index [ODI]), patient and clinician global impression of change (PGIC and CGIC), and patient satisfaction. Cluster analysis, Pearson's correlation coefficients, sensitivity, and specificity analyses were used to evaluate its utility in predicting higher patient functionality and satisfaction. Results: Though the term remission has been used in the chronic pain field, a consistent definition has not been previously established. Based on the analysis of the clinical data, we propose that a sustained (>= 6 months) pain score of <= 3.0 cm out of 10 cm on VAS be defined as remission. Applying this definition to the clinical trial data: subjects in remission at 24 months versus non-remitters were significantly more likely to be in the highest functional category of minimally disabled according to the ODI (31.5 vs. 8.2%, respectively, p = 0.001), and be 'very satisfied' (75.7 vs 22.6%, respectively, p < 0.001). Conclusions: The validity of the proposed definition of remission is supported by the persistence of remission in this study group, and its correspondence with patient satisfaction, and reduced disability. Further evaluation of the definition using clinical data from other long-term studies is needed.