Diagnosis of exclusion

A diagnosis of exclusion is an expression that in general applies to that diagnosis that is left over after all other possible differential diagnoses have been excluded. However some of the conditions for which the epithet of 'diagnosis of exclusion' are applied are actually verifiable but sometimes the rigmarole of doing so precludes it happening in the vast majority of real life situations e.g. a brain biopsy to prove Alzheimer disease or laparoscopic sampling of mesenteric nodes to confirm mesenteric adenitis.

Therefore, this definition can be tightened up further by suggesting that a true diagnosis of exclusion can only be used to apply to conditions that have no confirmatory test to prove that they are the diagnosis, i.e. they are purely clinical diagnoses. The archetypal example of a disease in this category is adult onset Still disease for which no confirmatory test exists.

Other conditions which are purely clinical diagnoses follow:

• irritable bowel syndrome (IBS)
• panic attack
• takotsubo cardiomyopathy (post liver transplant)
• Bell palsy
• anorexia tardive
• phantom tooth pain
• non-fatal amniotic fluid embolism
• hysterical stridor
• chronic idiopathic angioedema–urticaria
• functional vision loss
• psychogenic cough
• chronic bronchitis
• pyoderma gangrenosum
• trochanteric syndrome

Conditions that are generally diagnosed clinically but in theory could be diagnosed with a confirmatory test:

• Alzheimer disease
• mesenteric adenitis
• primary angiitis of the central nervous system