To investigate the clinical characteristics and outcome of patients with undiagnosed fever of unknown origin(FUO).

To retrospectively review the clinic data of patients discharged with FUO from the Department of General Internal Medicine, Peking Union Medical College Hospital during 2004 to 2008. Medical records and phone call follow–up data were collected until 2014.

Among 758 in–patients diagnosed with FUO, 70 patients still discharged with FUO were enrolled in this study, including 23 males and 47 females. There were 14 missing patients. Finally, definite diagnoses were made in 20 patients by clinical reassessments, empirical therapy or repeated biopsies, in whom 3 patients dying from underlying diseases. A total of 36 patients did not get final diagnoses, while fever was relieved in 23 patients, including 10 treated with corticosteroids or non–steroid anti–inflammatory drugs(NSAIDs) from 1 month to 12 months due to suspected connective tissue diseases. Another 3 patients still had episodic fever. Seven patients died shortly after discharge. There were 3 dying in the long–term follow–up. The overall FUO–related mortality was 18.6%. Mortality was correlated with the number of dysfunctional organs, especially cytopenia, coagulation dysfunction, bleeding events, respiratory damage and acute renal failure with OR 2.1, 9.9, 3.3 and 6.6(P<0.05) respectively.

Close follow–up, intermittent clinical reassessments, repeated biopsies will contribute to the diagnosis of patients discharged with FUO. Empirical therapy with corticosteroids, NSAIDs or anti–tubercular drugs in selected patients may be safe and effective. Mortality rates increased with impaired organs, especially the hematological, respiratory and renal systems.

Fever of unknown origin; Diagnosis; Prognosis; Follow–up study