Diagnosis of exclusion
A diagnosis of exclusion or by exclusion (per exclusionem) is a diagnosis of a medical condition reached by a process of elimination, which may be necessary if presence cannot be established with complete confidence from history, examination or testing. Such elimination of other reasonable possibilities is a major component in performing a differential diagnosis.
Diagnosis by exclusion tends to occur where scientific knowledge is scarce, specifically where the means to verify a diagnosis by an objective method is absent. As a specific diagnosis cannot be confirmed, a fall back position is to exclude that group of known causes that may cause a similar clinical presentation.
The largest category of diagnosis by exclusion is seen among psychiatric disorders where the presence of physical or organic disease must be excluded as a prerequisite for making a functional diagnosis.
Examples
An example of such a diagnosis is "fever of unknown origin": to explain the cause of elevated temperature the most common causes of unexplained fever (infection, neoplasm, or collagen vascular disease) must be ruled out.
Other examples include:
- Adult-onset Still's disease
- Behçet's disease
- Bell's palsy
- Burning mouth syndrome
- Chronic recurrent multifocal osteomyelitis
- Long COVID
- Psychogenic polydipsia
- Schizophrenia
- Somatic symptom disorder
- Sudden infant death syndrome
- Tolosa–Hunt syndrome