Longitudinal measurement invariance of the Behavioral Health Measure in a clinical sample.

The practice of routine outcome monitoring (ROM) has grown in popularity and become a fixture in feedback-supported clinical practice and research. However, if the interpretation of an ROM measure changes over time, treatment outcome scores may be inaccurate and produce erroneous or misguided interpretations of client progress and therapist efficacy. The current study examined whether factorial invariance held when using the Behavioral Health Measure (BHM-20) longitudinally in a clinical sample (n = 12,467). Using multidimensional item response theory-based models for the investigation of the BHM-20 factor structure, at a single time point and then longitudinally. Based on the original factor structure of the BHM-20 a unidimensional model, a three-factor orthogonal model, and a three-factor correlated model were fit to the data, indicating poor model fit with the proposed three-factor or unidimensional models. Next, using exploratory factor analysis and subsequent multidimensional item response theory procedures, a new 4-factor (General Distress, Life Functioning, Anxiety, and Alcohol/Drug Use) model was proposed with improved model-fit statistics. Finally, when testing the longitudinal invariance of the BHM-17 over 10 sessions of treatment, it was found to be fully consistent. The current study proposes the use of a 17-item, 4-factor model for a new understanding of the BHM-17. Implications for use in ROM and limitations are discussed. (PsycInfo Database Record (c) 2020 APA, all rights reserved).