At Completion of a Multidisciplinary Treatment Program, Are Psychophysical Variables Associated with a VAS Improvement of 30% or More, a Minimal Clinically Important Difference, or an Absolute VAS Score Improvement of 1.5 cm or More?

Objectives. Objectives were to determine at completion of a multidisciplinary pain program: 1) what percentage of chronic low back pain (CLBP) patients had improved at 30% or more (minimal clinically important difference [MCID]) and by 1.5 cm or more (minimal important change [MIC]) on the visual analog scale (VAS) and 2) whether that improvement is associated with pain matching (PM), pain threshold (PTRE), and pain tolerance (PTOL) improvements. Methods. One hundred and six CLBP patients had admission and discharge scores for VAS, PM, PTRE, and PTOL. Improvement was determined by absolute, MCID, and MIC VAS improvement. Logistic regression analysis controlling for age, gender, race, education, psychoactive substance dependence, and depression was utilized to develop models for the dependent variables of improvement of overall VAS; of MCID of 50% or more; and of MIC with PM, PTOL, and PTRE as independent variables. Results. Thirty-two percent and 35% of the CLBP patients were at MCID and MIC, respectively, at discharge (68% and 65% not at MCID and MIC, respectively), and 54.7% were improved overall. Of the improved patients, 59% were at MCID and 63.7% at MIC. PM was associated with overall VAS improvement, while PTRE and PM were associated with MCID improvement. MIC and 50% or above models could not be estimated. Limitations. The VAS was treated as a ratio scale. Conclusions. A significant percentage of CLBP patients were at MCID and at MIC at completion of multidisciplinary treatment. PM was associated with overall VAS improvement, while PTRE and PM were associated with MCID.