Fever of unknown origin in the 2000s: evaluation of 103 cases over eleven years

Presse Med. 2014 Sep;43(9):e233-40. doi: 10.1016/j.lpm.2014.02.026. Epub 2014 Jun 28.


Purpose: Despite recent diagnostic advances, a fever of unknown origin (FUO) remains a clinical challenge.

Methods: This study reports the clinical courses and outcomes of 103 cases of FUO and evaluates the places of (18)F-Fluorodeoxyglucose positrons emission tomography ((18)FDG-PET) and molecular biology in the diagnostic approach.

Results: This retrospective study was carried out from 2002 to 2012 in two departments of internal medicine. The diagnosis of FUO was based on the updated criteria of Durack and Street. It included 54 men and 49 women (mean age: 57 years) in 52 of whom the final diagnosis could not be established. Among the 51 patients with final diagnosis, non-infectious inflammatory disorders were the most prevalent (61%). The other diagnoses were infectious diseases (23.5%), miscellaneous causes (10%) and malignancies (6%). (18)FDG-PET was performed in 48 patients and was contributory in 10. Molecular biology techniques were performed in 28 patients and were contributory in only one case: detection of a cytomegalovirus infection by polymerase-chain-reaction assay. At study closure, eleven patients had died, of whom five died from the disease that caused the FUO. Only two deaths among the 52 patients without diagnosis could be attributed to the feverish illness.

Conclusion: As observed in the most recent case series, the rate of undiagnosed patients is increasing. The prognosis was good for undiagnosed FUO. Here, the yield of (18)FDG-PET was 21% but that of molecular biology negligible. The recourse to molecular biology seems useless unless directed by a high degree of clinical suspicion.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • DNA, Bacterial / analysis
  • DNA, Viral / analysis
  • Female
  • Ferritins / blood
  • Fever of Unknown Origin / etiology*
  • Fluorodeoxyglucose F18
  • Humans
  • Infections / complications
  • Infections / diagnosis
  • Inflammation / complications
  • Inflammation / diagnosis
  • Male
  • Middle Aged
  • Neoplasms / complications
  • Neoplasms / diagnosis
  • Polymerase Chain Reaction
  • Positron-Emission Tomography
  • Radiopharmaceuticals
  • Retrospective Studies
  • Young Adult


  • DNA, Bacterial
  • DNA, Viral
  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18
  • Ferritins