Interpreting Biochemical Data In the Context of Eating Disorders

Pathology results and biochemical data should be assessed and monitored regularly throughout treatment. The frequency will depend on diagnosis and medical acuity.

It is important to note that pathology results may be within normal limits even with significant malnutrition and are therefore not indicative of nutritional stability in individuals with eating disorders (AED, 2016). Any abnormal findings should be taken seriously, as they usually indicate severe and long- term nutritional deficiency (Setnick, 2011).

Glucose

• Relationship to eating disorders: Indicator of bloodstream energy supply

• Potential abnormal finding:

• • High: Can indicate Type 2 Diabetes, Type 1 Diabetes – newly diagnosed or previously diagnosed but with inadequate insulin administration

  • Low: Can indicate acute malnutrition, too long without eating, inadequate carbohydrate intake, excess insulin administration

Sodium

• Relationship to eating disorders: Indicator of fluid balance

• Potential abnormal finding:

• • High: Can indicate dehydration

  • Low: Can indicate water loading, laxatives, diuretics

Potassium

• Relationship to eating disorders: Indicator of nutrition status

• Potential abnormal finding:

• • High: Can indicate dehydration due to inadequate fluid intake, untreated diabetes, excessive potassium supplementation

  • Low: Can indicate refeeding syndrome, malnutrition, vomiting, dehydration due to diarrhoea, abuse of diuretics or laxatives

Chloride

• Relationship to eating disorders: Indicator of fluid and electrolyte balance

• Potential abnormal finding:

• • Low: Can indicate vomiting, laxatives, diuretics

Ferritin

• Relationship to eating disorders: Most sensitive indicator of iron status

• Potential abnormal finding:

• • High: Can indicate excessive iron supplementation

  • Low: Can indicate inadequate dietary intake of iron

Folate, Vitamin B-9

• Relationship to eating disorders: Indicator of nutrition (note: deficiency can cause altered mental status)

• Potential abnormal finding:

• • High: Can indicate pernicious anaemia, liver dysfunction

  • Low: Can indicate malnutrition, alcohol abuse, coeliac disease, Crohn's disease, haemolytic anaemia

Bicarbonate

• Relationship to eating disorders: Indicator of pH balance

• Potential abnormal finding:

• • High: Can indicate vomiting

  • Low: Can indicate laxatives

Blood Urea Nitrogen

• Relationship to eating disorders: Evaluates kidney function, which can be compromised in severe cases of eating disorders

• Potential abnormal finding:

• • High: Can indicate dehydration, catabolism of muscle, excessive dietary protein intake, impaired kidney function

  • Low: Can indicate starvation, overhydration

Creatinine

• Relationship to eating disorders: Evaluates kidney function which can be compromised in severe eating disorders

• Potential abnormal finding:

• • High: Can indicate dehydration, muscle injury, impaired kidney function

  • Low: Can indicate muscle wasting, poor muscle mass

Calcium

• Relationship to eating disorders: Blood calcium levels do not reflect dietary calcium intake

• Potential abnormal finding:

• • Low: Can indicate malnutrition, magnesium or vitamin D deficiency

Phosphate

• Relationship to eating disorders: indicator of nutrition status

• Potential abnormal finding:

• • High: Can indicate excessive supplementation

  • Low: Can indicate refeeding syndrome, vomiting, laxative or diuretic abuse, alcohol abuse, thyroid disease, untreated diabetes, kidney disease, malabsorption, recent iron infusion

Magnesium

• Relationship to eating disorders: Indicator of kidney and GI function

• Potential abnormal finding:

• • High: Can indicate dehydration, laxative abuse, excessive use of over the counter antacids containing magnesium

  • Low: Can indicate inadequate dietary intake of magnesium, diuretic or laxative abuse, alcohol abuse, inflammatory bowel disease (IBD), coeliac disease

Albumin

• Relationship to eating disorders: indicator of nutrition status

• Potential abnormal finding:

• • High: Can indicate early malnutrition at the expense of muscle mass

  • Low: Can indicate malnutrition, inflammation, shock, liver disease, Crohn's disease, coeliac disease

Total Protein

• Relationship to eating disorders: indicator of nutrition status

• Potential abnormal finding:

• • High: Can indicate early malnutrition at the expense of muscle mass

  • Low: Can indicate inadequate dietary intake of protein, coeliac disease, irritable bowel disease

Amylase

• Relationship to eating disorders: Digestive enzyme produced mainly in salivary glands and pancreas. When either of these is inflamed, amylase escapes into the blood. Salivary isoamylase may be ordered when a patient is suspected of, but denies self-induced vomiting

• Potential abnormal finding:

• • High: Can indicate self-induced vomiting, cholecystitis or obstruction of the salivary glands, intestinal obstruction, pancreatic or bile duct obstruction, perforated ulcer, tubal pregnancy (may be ruptured), viral gastroenteritis, macroamylasemia

  • Low: Can indicate low carbohydrate intake, damage to the pancreas, kidney disease, pancreatic cancer, toxaemia of pregnancy

Liver Function Tests (LFTs): Aspartate Aminotransaminase (AST), Alanine aminotransaminase (ALT), alkaline phosphate (ALP)

• Relationship to eating disorders: Evaluated liver function, which can be compromised in severe cases of eating disorders

• Potential abnormal finding:

• • High: Can indicate malnutrition, substance abuse (including alcohol, drugs, steroids), nutrition rehabilitation when refeeding

Leptin

• Relationship to eating disorders: Endogenous appetite suppressant

• Potential abnormal finding:

• • Low: Can indicate undernutrition

Haematocrit (HCT)

• Relationship to eating disorders: Indicator of nutrition status

• Potential abnormal finding:

• • High: Can indicate dehydration, polycythaemia, blood doping, anabolic steroid use

  • Low: Can indicate malnutrition, iron deficiency

Haemoglobin (Hgb)

• Relationship to eating disorders: Indicator of nutrition status

• Potential abnormal finding:

• • High: Can indicate dehydration

  • Low: Can indicate malnutrition, iron deficiency

Glycosylated Haemoglobin (Hb A 1 c)

• Relationship to eating disorders: Measurement of blood glucose control over time

• Potential abnormal finding:

• • High: Can indicate poor glucose control, binge eating with type 2 diabetes, underuse of insulin with type 1 diabetes

Iron

• Relationship to eating disorders: Indicator of nutrition status; deficiency can cause headache, fatigue and difficulty concentrating

• Potential abnormal finding:

• • High: Can indicate excessive iron supplementation, haemochromatosis

  • Low: Can indicate inadequate dietary intake of iron, vegetarian/vegan dietary intake, heavy or long duration menstruation, rapid growth in children

Red blood cell count (RBC)

• Relationship to eating disorders: Can be altered by fluid and nutrition status

• Potential abnormal finding:

• • High: Can indicate dehydration

  • Low: Can indicate iron deficiency

Urine output

• Relationship to eating disorders: Indicator of fluid balance

• Potential abnormal finding:

• • High: Can indicate excessive fluid intake. inadequate sodium intake

  • Low: Can indicate dehydration

Urine specific gravity

• Relationship to eating disorders: Measurement of dehydration

• Potential abnormal finding:

• • High: Can indicate dehydration, diarrhoea

  • Low: Can indicate renal failure, diabetes insipidus, excessive fluid intake

Vitamin B-12

• Relationship to eating disorders: Indicator of nutrition status, deficiency can cause altered mental status, contributes to depression

• Potential abnormal finding:

• • Low: Can indicate pernicious anaemia, vegetarian/vegan dietary intake (naturally occurs mainly in animal products)

AED. (2016). Eating Disorders: A Guide to Medical Care. Critical points for Early Recognition and Medical Risk Management in the Care of Individuals with Eating Disorders (3rd ed.). Reston: Academy for Eating Disorders. Accessed online: http://www.nyeatingdisorders.org/pdf/AED%20Medical%20Management%20Guide%203rd%20Edition.pdf

Gaudiani, J. (2018). Sick Enough: A Guide to the Medical Complications of Eating Disorders. New York: Routledge.

Setnick, J. (2011). Academy of Nutrition and Dietetics Pocket Guide to Eating Disorders (2nd ed.). Chicago: Academy of Nutrition and Dietetics.

Wolf, M., Rubin, J., Achebe, M., Econs, M. J., Peacock, M., Imel, E. A., Thomsen, L. L., Carpenter, T. O., Weber, T., Brandenburg, V., & Zoller, H. (2020). Effects of Iron Isomaltoside vs Ferric Carboxymaltose on Hypophosphatemia in Iron-Deficiency Anemia. JAMA, 323(5), 432-443. doi: 10.1001/jama.2019.22450