CRS - Anorexia Nervosa

Explanation

Serum biochemistry will be important if Alice has been vomiting, as prolonged vomiting may lead to electrolyte abnormalities. The most important abnormality to look for is hypokalaemia which can lead to cardiac arrhythmia.

Other investigations should be ordered depending on findings on history and examination such as:  

1. Excluding other causes of weight loss,
- For example: full blood count,  stool examination (microscopy of stool for ova/cysts/spores, stool culture for organisms , faecal fat estimation if history suggestive of malabsorption), inflammatory markers (ESR, CRP)
- Tests to determine utilisation/metabolism: urinalysis, signs of loss of nutrients in urine (ketones and sugar)
- Tests to determine energy expenditure: hormone levels (e.g. thyroid function).

2. Complications of anorexia nervosa            
- Full blood count (anaemia, neutropenia)            
- Electrolytes, serum calcium, magnesium, phosphate (hypokalaemia)
- Liver function tests (severe weight loss may result in transaminitis)
- oestradiol, LH, FSH (amenorrhoea)
- ECG ( arrhythmia, prolonged QT interval)
- Urinalysis ( raised pH in catabolic state, ketones, low specific gravity if water loaded or high specific gravity if dehydrated)