From the Guidelines
Both chloride and bicarbonate are crucial to test in initial labs for eating disorders, as they provide essential information about the patient's electrolyte balance and potential complications associated with purging behaviors. These electrolytes should be included in a comprehensive metabolic panel when evaluating patients with suspected eating disorders, particularly anorexia nervosa and bulimia nervosa, as recommended by the American Psychiatric Association 1. Chloride levels can be altered in patients who purge through vomiting, as they lose hydrochloric acid from the stomach, potentially leading to hypochloremic metabolic alkalosis. Bicarbonate levels are equally important as they often increase in response to vomiting-induced acid loss, resulting in metabolic alkalosis. Additionally, laxative abuse can cause bicarbonate loss and metabolic acidosis. These electrolyte disturbances can have serious cardiac consequences, including arrhythmias. The pattern of electrolyte abnormalities (particularly the relationship between chloride and bicarbonate) can provide diagnostic clues about purging behaviors even when patients don't disclose them. Some key points to consider when evaluating patients with eating disorders include:
- The importance of a comprehensive review of systems, as recommended by the American Psychiatric Association 1
- The need for a complete blood count and a comprehensive metabolic panel, including electrolytes, liver enzymes, and renal function tests, as recommended by the American Psychiatric Association 1
- The potential for electrolyte disturbances, such as hypochloremic metabolic alkalosis and metabolic acidosis, and their associated cardiac consequences
- The importance of assessing for other complications of eating disorders, such as hypokalemia, hypoglycemia, and bone marrow suppression. Initial labs should also include sodium, potassium, glucose, BUN, creatinine, and a complete blood count to assess for these complications.
From the Research
Importance of Chloride and Bicarb in Eating Disorder Initial Labs
- Electrolyte abnormalities, including hyponatremia, hypokalemia, and metabolic alkalosis, are common in eating disorders and can vary depending on whether patients engage in purging behaviors 2, 3.
- Chloride levels can be an important indicator of purging behaviors, as the ratio of urine sodium to urine chloride was found to be a useful predictor of bulimic behavior 4.
- Bicarb levels can also be affected in eating disorders, particularly in patients with purging behaviors, who may develop metabolic alkalosis 2, 3.
- Laboratory tests, including electrolyte panels, can be useful in evaluating patients with eating disorders, but may not always be abnormal, even in patients with severe malnutrition 5.
- Renal function should also be evaluated in patients with eating disorders, as they are at risk for renal complications, including acute renal injury and chronic kidney disease 3, 6.
- The choice of laboratory tests and equations used to estimate renal function can be important, as different formulas may yield different results in patients with eating disorders 6.