Identification of anorexia nervosa

The primary care team may have the opportunity to screen high-risk groups and is also likely to be the first point of contact with the patient. Frequently initial contact was made by a worried relative or school teacher who has observed weight loss or specific food related behaviours such as skipping meals, hiding food or adopting a restricted diet. Indeed any of the physical, psychological or social behaviours listed.

There is a danger that the inexperienced practitioner may make light of the symptoms or feel that they are self-inflicted. The history must be taken with a sympathetic ear and in an empathetic and non-judgemental manner. A careful history should be taken and matched against the diagnostic criteria. The mean age of onset is 16-17.

The NICE guidance lists the following factors to be considered

  • Risk factors – family history of eating disorder, Type 1 diabetes, previously overweight, occupation (e.g. athlete, dancer, model). Although adolescent girls and young women constitute the principal population at risk, it should be remembered that eating disorders also occur in ethnic minorities, men and children.
  • Differential diagnosis of weight loss – includes malabsorbtion (e.g. coeliac disease, inflammatory bowel disease), neoplasm, illicit drug use, infection (e.g. TB), autoimmune disease, endocrine disorders (e.g. hyperthyroidism).
  • Differential diagnosis of amenorrhoea – includes pregnancy, primary ovarian failure, polycystic ovary syndrome, pituitary prolactinoma, uterine problems and other hypothalmic causes.
  • Psychiatric differential diagnosis – includes depression, obsessive-compulsive disorder, somatisation and, rarely, psychosis.

A physical examination is required to calculate the BMI (or use centile charts for persons aged less than 18), pulse and blood pressure should be taken. In patients showing a degree of emaciation, core temperature examination of the peripheries for circulation and oedema, a check for postural hypotension and a squat test to check muscle power should also be performed. The patient is asked to squat and then rise without using their arms. If the patient needs to use their arms to balance then this may indicate a moderate risk, if the patient needs to use their arms to leverage themselves up this is an indication of profound muscle weakness and high risk.

Full blood count, ESR, U+E, Creatinine, liver function tests, random blood glucose and urinalysis would screen for most of the common differential diagnoses. An ECG may be appropriate particularly if there is bradycardia, electrolyte imbalance or a BMI of less than 15. In more severe cases calcium, magnesium, phosphate, serum proteins and creatinine kinase may also be required. In the differential diagnosis of amenorrhoea with weight loss thyroid function, follicle stimulator hormone, luteinising hormone, prolactin and a chest x-ray should be performed.

A DEXA scan may be required to identify bone loss in chronic cases or in cases with prolonged amenorrhoea.

The Royal College of Psychiatrists has produced an algorithm for the initial diagnosis and management of suspected cases of eating disorder.



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