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November 14, 1977

Fever of Unknown OriginAn Algorithmic Approach

JAMA. 1977;238(20):2183-2188. doi:10.1001/jama.1977.03280210075034

FEVER of unknown origin (FUO) has been regarded as a supreme diagnostic puzzle. This reputation may be undeserved, since there is a tendency to group under this heading many specific syndromes that include fever as one of their symptoms. The term "FUO" should be reserved for a syndrome in which the fever is prolonged and there are no other specific signs or symptoms that would define a separate syndrome. The first criterion is recognized generally, but neglect of the second has resulted in the implication that fevers associated with polyarthritis, abdominal pain, or rash are all FUOs and may be approached similarly. A third criterion, that the fever is undiagnosed after routine diagnostic tests, is sometimes applied but is too vague to be satisfactory.

The algorithms presented here provide a logical, step-by-step approach to the FUO syndrome. The essential features of this approach are (1) limitation of associated symptoms to