Sensitivity to change of scales assessing symptoms of bulimia nervosa.

Measures employed in a therapy study with a pre-post design must be sensitive to the detection of treatment-related changes. In the present study, the treatment sensitivity of 12 internationally established scales that assess bulimia-relevant aspects of eating and body concern is analyzed. The scales can be sorted along three dimensions (Disturbed Eating, Restrictive Eating Behaviors and Body Dissatisfaction). Measures of the same dimension were compared in a sample of 45 women with the diagnosis of bulimia nervosa. Patients completed the scales before and 6 weeks after the end of cognitive-behavioral therapy. Significant differences between scales with respect to treatment sensitivity occurred in all three dimensions. Post hoc analysis revealed that scales are particularly sensitive to change if they include disorder-relevant aspects beyond the main dimension of a scale. Implications of the findings for meta-analytical treatment research, for designing effectiveness studies, and for future research on the treatment sensitivity of outcome measures are discussed.