Mortality in patients presenting with fever of unknown origin

Background: Few data exist on the contemporary prognosis of patients presenting with fever of unknown origin (FUO).

Methods: The data of 436 adult immunocompetent patients presenting with FUO between 2000 and 2010 and followed for at least 6 months were analyzed, with a focus on FUO-related deaths. The following variables were assessed in survivors and non-survivors: age, underlying diagnosis, and, in a nested case-control design, fever periodicity, selected laboratory parameters (including peripheral blood counts, enzymes, and inflammatory markers) and organomegaly.

Results: Thirty FUO-related deaths occurred (6·9%). Malignancy accounted for 11% of fevers but for 60% of deaths. Especially non-Hodgkin lymphoma carried a disproportionally high death toll. In the non-malignant categories, fatality rates were below 6%. All patients discharged without diagnosis in spite of ample investigations (n = 164) survived. Besides malignancy, age, continuous (as opposed to episodic) fever, anaemia, leucopenia, LDH levels, and hepatomegaly were associated with mortality.

Conclusions: Fatality rates of FUO have continuously declined over the past decades. Malignancy, including lymphoma, remains a cardinal cause of death. Patients with FUO discharged without diagnosis survive.