Evaluating the predictive validity of purging disorder by comparison to bulimia nervosa at long-term follow-up

Abstract

Objective: The current study sought to examine the predictive validity of the purging disorder diagnosis at long-term follow-up by comparing naturalistic outcomes with bulimia nervosa.

Method: Women with purging disorder (N = 84) or bulimia nervosa (N = 133) who had completed comprehensive baseline assessments as part of one of three studies between 2000 and 2012 were sought for follow-up assessment. Nearly all (94.5%) responded to recruitment materials and 150 (69% of sought sample; 83.3% non-Hispanic white; 33.40 [7.63] years old) participated at an average of 10.59 (3.71) years follow-up. Participants completed the Eating Disorder Examination, the Structured Clinical Interview for DSM-IV, and a questionnaire battery. Diagnostic groups were compared on eating disorder (illness status, recovery status, and eating pathology) and related outcomes. Group differences in predictors of outcome were explored.

Results: There were no significant differences in eating disorder presence (p = .70), recovery status (p = .87), and level of eating pathology (p = .17) between diagnostic groups at follow-up. Post hoc equivalence tests indicated group differences were smaller than a medium effect size (p's ≤ .005). Groups differed in diagnosis at follow-up (p = .002); diagnostic stability was more likely than cross-over to bulimia nervosa for women with baseline purging disorder (p = .004).

Discussion: Although purging disorder and bulimia nervosa do not differ in long-term outcomes, the relative stability in clinical presentation suggests baseline group differences in clinical presentation may be useful in augmenting treatments for purging disorder.

Public significance statement: While purging disorder is classified as an "other specified" eating disorder, individuals who experience this disorder have comparable negative long-term outcomes as those with bulimia nervosa. This highlights the importance of screening for and treating purging disorder as a full-threshold eating disorder.

Keywords: bulimia nervosa; follow-up; other specified feeding or eating disorder; outcome; purging disorder.