What laboratory tests should be ordered for an eating disorder referral?

Laboratory Tests for Eating Disorder Referral

For eating disorder referrals, a complete blood count and comprehensive metabolic panel (including electrolytes, liver enzymes, and renal function tests) are the essential laboratory tests that should be ordered. 1

Core Laboratory Tests

• Complete blood count (CBC) - To assess for anemia, leukopenia, and other hematologic abnormalities commonly seen in malnutrition 1, 2
• Comprehensive metabolic panel including: 1
  • Electrolytes (sodium, potassium, chloride, bicarbonate) - To detect hyponatremia, hypokalemia, hypochloremia, and metabolic alkalosis, particularly in patients with purging behaviors 1, 2, 3
  • Liver enzymes - To assess hepatic function which may be affected in malnutrition 1, 2
  • Renal function tests (BUN, creatinine) - To evaluate kidney function and hydration status 1

Additional Testing Based on Clinical Presentation

• Electrocardiogram (ECG) - Recommended for patients with: 1

  • Restrictive eating disorders (e.g., anorexia nervosa)
  • Severe purging behaviors
  • Patients taking medications known to prolong QTc intervals 1

• Additional laboratory tests to consider based on specific symptoms and behaviors:

  • Phosphate levels - Particularly important during refeeding to monitor for refeeding syndrome 2
  • Magnesium levels - May be depleted in patients with chronic malnutrition or purging 4
  • Glucose levels - To detect hypoglycemia, which occurs in approximately 22% of eating disorder patients and is more common in those with low BMI 5
  • Prealbumin - To assess nutritional status, found to be low in over 50% of patients with restrictive anorexia nervosa 2

Clinical Correlation

The laboratory assessment should be interpreted in the context of:

• Vital signs including temperature, resting heart rate, blood pressure, orthostatic pulse, and orthostatic blood pressure 1
• Anthropometric measurements including height, weight, and BMI (or percent median BMI, BMI percentile, or BMI Z-score for children and adolescents) 1
• Physical appearance including signs of malnutrition or purging behaviors 1

Common Laboratory Abnormalities by Eating Disorder Type

• Anorexia Nervosa - Restricting Type: 2

  • Leukopenia (36.1%)
  • Low prealbumin (51.4%)
  • Hyponatremia (16.0%)
  • Hypokalemia (14.2%)
  • Hypoglycemia (7.1%)

• Anorexia Nervosa - Binge/Purge Type: 2

  • Hypokalemia (42.4%)
  • Metabolic alkalosis (33.3%)
  • Prolonged QTc intervals

• Bulimia Nervosa: 2, 3

  • Hypokalemia (26.2%)
  • Metabolic alkalosis (23.4%)
  • Elevated serum amylase (associated with frequent binge-eating and vomiting)

Important Considerations

• Laboratory abnormalities are present in nearly half (48.8%) of patients with eating disorders 3
• The severity and number of medical complications increase with the severity of the eating disorder 2
• Purging behaviors significantly increase the risk of electrolyte disturbances 2, 3
• Early detection and monitoring of these abnormalities is crucial as eating disorders have a mortality rate nearly 6 times higher than age-matched individuals without eating disorders 6