Serum electrolytes as markers of vomiting in bulimia nervosa.

OBJECTIVE

Patients with bulimia nervosa often have serum electrolyte abnormalities that result from vomiting and/or laxative or diuretic use. Thus, serum electrolytes could serve as an objective marker of such behaviors.

METHOD: This study is a retrospective examination of serum electrolyte levels and vomiting behavior in 138 bulimic women, and of serum electrolyte levels in 70 control women.

RESULTS

Logistic regression analyses demonstrated that only potassium values distinguished bulimic subjects from controls. Potassium levels below the lower limit of normal (3.7 mg/l) occurred only in the bulimic group.

DISCUSSION: Abnormally low values for potassium are a specific, but not sensitive, predictor of recent vomiting episodes.