Urinary Electrolytes Help Uncover Bulimic Behavior

Bulimic patients are notoriously secretive about their behavior, making it difficult to detect their bingeing and purging. However, 2 urinary electrolytes are particularly clinical markers of bulimic behavior. At the recent Eating Disorders Research Society meeting in Cambridge, MA, Scott Crow, MD, and colleagues from the University of Minnesota described a study of 77 women with bulimia nervosa (BN) and 53 healthy controls. Urine and serum electrolytes plus a urine phenolphthalein screen were taken of all subjects. BN patients also filled out an Eating Behaviors-IV form to assess the severity of their symptoms. The fractional excretion of sodium (FENA) was the most sensitive urinary electrolyte value: it identified 37.2% of BN subjects. The urine anion gap (UAG) identified 27.9% and serum potassium detected 29.78% of BN patients. A combination of the 3 lab tests identified 55.2% of BN subjects. Both the UAG and FENA values could be correlated with frequency of vomiting, but the urinary potassium values could not.