A retrospective analysis of 3156 admissions with fever of unknown origin in a large Italian hospital.

Background: fever of unknown origin (FUO) is defined as a fever with no etiologic diagnosis after standardized investigations performed during 3 days in hospital or after at least 3 ambulatory visits. Our study aims to describe the epidemiology of classic FUO through the retrospective analysis of 902 861 admissions to a large University Hospital in Italy, to investigate its temporal trend, and to evaluate differences between young and old patients. Methods: we retrieved data records of all the admissions between the 1st January 1988 and 31st December 2007. Proportional admission rate (PAR) of FUO was calculated. Time trends of FUO admissions were analysed by joinpoint regression, with time changes expressed as Expected Annual Percent Change (EA PC). The ICD 9-CM code was used to identify the diagnosis on discharge of FUO cases. Results: in the study period 3 156 patients were admitted with a diagnosis of FUO (PAR=3.50 per 1 000). The time-trend analysis showed two joinpoints, the first in 1995 (EAPC of 307.80, 95% CI: 89.66-776.84, p=0.002), and the second in 1998 (EAPC=-8.57, 95% CI: -10.37-6.73; p<0.001). Around 22% of admissions remained without a definitive diagnosis of FUO, with this percentage being lower in patients ≥65 years compared with subjects aged 21-64. ConclusionS: FUO is a leading cause of admission to hospitals, as well as of morbidity and mortality, thus representing a challenge for diagnostic medicine and hospital care. It is necessary to develop a diagnostic methodology for FUO, so as to reduce costs of preventable hospitalizations.