title: Diagnostic workup for fever of unknown origin: a multicenter collaborative retrospective study.
abstract: OBJECTIVE
  Fever of unknown origin (FUO) can be caused by many diseases, and varies depending on region and time period. Research on FUO in Japan has been limited to single medical institution or region, and no nationwide study has been conducted. We identified diseases that should be considered and useful diagnostic testing in patients with FUO.
  
  
  METHODS
  A nationwide retrospective study.
  
  
  METHODS
  17 hospitals affiliated with the Japanese Society of Hospital General Medicine.
  
  
  METHODS
  This study included patients ≥18 years diagnosed with 'classical fever of unknown origin' (axillary temperature ≥38°C at least twice over a ≥3-week period without elucidation of a cause at three outpatient visits or during 3 days of hospitalisation) between January and December 2011.
  
  
  RESULTS
  A total of 121 patients with FUO were enrolled. The median age was 59 years (range 19-94 years). Causative diseases were infectious disease in 28 patients (23.1%), non-infectious inflammatory disease in 37 (30.6%), malignancy in 13 (10.7%), other in 15 (12.4%) and unknown in 28 (23.1%). The median interval from fever onset to evaluation at each hospital was 28 days. The longest time required for diagnosis involved a case of familial Mediterranean fever. Tests performed included blood cultures in 86.8%, serum procalcitonin in 43.8% and positron emission tomography in 29.8% of patients.
  
  
  CONCLUSIONS
  With the widespread use of CT, FUO due to deep-seated abscess or solid tumour is decreasing markedly. Owing to the influence of the ageing population, polymyalgia rheumatica was the most frequent cause (9 patients). Four patients had FUO associated with HIV/AIDS, an important cause of FUO in Japan. In a relatively small number of cases, cause remained unclear. This may have been due to bias inherent in a retrospective study. This study identified diseases that should be considered in the differential diagnosis of FUO.
authors.affiliation: Department of General Medicine, Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Naito
authors.forename: Masafumi
authors.initials: M
authors.lastname: Mizooka
authors.forename: Fujiko
authors.initials: F
authors.lastname: Mitsumoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Kanazawa
authors.forename: Keito
authors.initials: K
authors.lastname: Torikai
authors.forename: Shiro
authors.initials: S
authors.lastname: Ohno
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Morita
authors.forename: Akira
authors.initials: A
authors.lastname: Ukimura
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Mishima
authors.forename: Fumio
authors.initials: F
authors.lastname: Otsuka
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Ohyama
authors.forename: Noriko
authors.initials: N
authors.lastname: Nara
authors.forename: Kazunari
authors.initials: K
authors.lastname: Murakami
authors.forename: Kouichi
authors.initials: K
authors.lastname: Mashiba
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Akazawa
authors.forename: Koji
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Shoichi
authors.initials: S
authors.lastname: Senda
authors.forename: Masashi
authors.initials: M
authors.lastname: Yamanouchi
authors.forename: Susumu
authors.initials: S
authors.lastname: Tazuma
authors.forename: Jun
authors.initials: J
authors.lastname: Hayashi
keywords: INTERNAL MEDICINE