A baseline comparison of three diagnostic groups using the Progress Monitoring Tool for Eating Disorders

Utilisation of intensive inpatient treatment for eating disorders (EDs) has climbed in the last decade, illuminating a need for better consensus on what constitutes effective treatment and context-appropriate progress/outcome monitoring during residential stays. The novel Progress Monitoring Tool for Eating Disorders (PMED) measure is specifically designed for inpatient settings. Previous research supports the factorial validity and internal consistency of the PMED; however, additional work is needed to determine its appropriateness for complex patient populations. This study used measurement invariance (MI) testing to determine if the PMED administered at programme admission measures the same items in similar ways across patients with anorexia nervosa restricting- and binge-purge subtypes (AN-R; AN-BP) and bulimia nervosa (BN, N = 1121; M_age  = 24.33 years, SD = 10.20; 100% female). Progressively constrained models were used to determine the level of invariance upheld between the three groups. Results indicated that, while the PMED meets configural and metric MI, it does not display scalar invariance. Said otherwise, the PMED similarly assesses constructs and items across AN-R, AN-BP, and BN, however the same score overall may reflect different levels of psychopathology for patients in one diagnostic category versus another. Comparisons of severity between different EDs should be made with caution, however the PMED appears to be a sound tool for understanding the baseline functioning of patients with EDs in an inpatient setting.