Prediction of treatment outcome from clinically derived MMPI clusters in rehabilitation for chronic low back pain.

OBJECTIVE

The aim of this study was to assess the ability of specific and clinically relevant Minnesota Multiphasic Personality Inventory (MMPI) profile types to predict outcomes in a structured interdisciplinary pain-management program for patients with low back pain.

DESIGN

Subjects were divided into clusters representing MMPI profiles yielding similar clinical interpretation. Analyses of variance and chi-square testing assessed the effect of cluster group on a variety of outcome measures at pretreatment, posttreatment, and 6- to 66-month follow-up. Fisher's Least Significant Difference Test assessed the significance of differences between pairs of cluster groups.

SETTING

A university-based comprehensive interdisciplinary pain-management program serving both inpatients and outpatients.

PATIENTS

122 subjects with chronic low back pain who completed the program, provided follow-up data, and fit into the definition of one of seven clusters.

MAJOR OUTCOME MEASURES

Self-reports of subjective pain intensity, pain-related medication intake, and activity level at pretreatment, posttreatment, and follow-up; employment status at pretreatment and follow-up.

RESULTS

Cluster groups did not differ significantly at any time on activity level and medication intake and differed on employment status only at pretreatment. There was a significant (p < 0.05) effect of cluster group on subjective pain intensity, but only two pairwise group comparisons were significant: subjects with a normal MMPI profile and those with no elevations except T = 71-80 on Hypochondriasis and Hysteria reported less pain at follow-up than did subjects with extreme elevations (T > 80) on both Hypochondriasis and Hysteria.

CONCLUSION

Even when subjects with chronic pain are divided into cluster groups associated with highly similar clinical interpretations, the MMPI for the most part fails to predict self-reported outcomes in an interdisciplinary pain-management program.