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 measurechanges over time, treatment outcome scores may be inaccurate and produce erroneous or misguidedinterpretations of client progress and therapist efficacy. The current study examined whether factorialinvariance 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 theBHM-20 factor structure, at a single time point and then longitudinally. Based on the original factorstructure of the BHM-20 a unidimensional model, a three-factor orthogonal model, and a three-factorcorrelated model were fit to the data, indicating poor model fit with the proposed three-factor orunidimensional models. Next, using exploratory factor analysis and subsequent multidimensional itemresponse 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 longitudinalinvariance of the BHM-17 over 10 sessions of treatment, it was found to be fully consistent. The currentstudy proposes the use of a 17-item, 4-factor model for a new understanding of the BHM-17.