(226) The reliability of the Millon Behavioral Medicine Diagnostic for Presurgical Bariatric Weight Loss Evaluations

Objective: The Millon Behavioral Medicine Diagnostic (MBMD) is routinely used in presurgical bariatric evaluations to evaluate individuals’ experience of their health, response to medical concerns in relation to treatment recommendations, history of adherence to treatment plans, and typical coping skills. Researchers (Walfish, Wise, & Streiner, 2008) raised concern that 16 of the 32 scales did not meet minimal standards of use (as defined by a Cronbach’s Alpha of >.69) within bariatric populations, and 13 of the remaining scales lacked strong evidence of reliability. The present study aimed to assess MBMD scale consistency examining a bariatric population independent of the original sample.

Method: Archival data from an independent sample of adult bariatric surgery candidates included 759 patients (Age: 46.1 [SD=12.0]; 84% female; 87% White, Non-Hispanic). We estimated internal consistency for each of the 32 scales of the MBMD. Our study sample size was adequately powered (80%) at an alpha of 0.05 for scale sizes ranging from 5 to 25 items to test a null hypothesis.

Results: Of the 32 scales, 19 (59%) had a Cronbach’s Alpha value ≥0.70, primarily including bariatric patients’ psychiatric indications (e.g., depression, anxiety) and stress moderation (e.g., social isolation, future pessimism).

Conclusion: These findings suggest 13 of the 32 scales in the MBMD are not consistently measuring unified concepts. Immediate future steps include further examination of internal consistency on the scale and item level. Additionally, examining internal consistency at the item level would be helpful in the development of a reliability index for individual response styles.