OBJECTIVETo investigate the distribution and change of the causes of fever of unknown origin(FUO).

METHODSThe clinical data of 500 inpatients with FUO in our center between December 2003 and June 2014 were retrospectively analyzed. The diagnostic methods,etiologies,and their possible relationship with age,sex,fever duration,and period.

RESULTSOf these 500 FUO patients,452(90.4%)were confirmed to be with fever caused by conditions including infectious diseases [(n=231,46.2%;e.g.tuberculosis(32.9%,76/231)],connective tissue diseases(CTD)(n=99,19.8%),neoplasms(n=58,11.6%),miscellaneous causes(n=64,12.8%). The causes were not identified in 48 cases(9.6%).The proportion of CTD in female patients was significantly higher than that in male patients(26.3% vs. 14.5%,P=0.025),whereas the proportion of neoplasms in male patients was significantly higher than that in female patients(14.5% vs. 8.0%,P=0.001). Infectious diseases was the most common cause in all age groups,CTD ranked the second in the 21-39-year group and 40-59-year group,and neoplasm was the second most coomon cause in the over 60 year group. Thus,the distribution of FUO etiologies significantly differed in different age groups(χ(2)=43.10,P=0.000). The duration of fever in patients with neoplasms [60(28,90)d] was longer than that in patients with infectious diseases [28(21,42)d,Z=-4.168,P=0.000] or CTD [30(21,60)d,Z=-2.406,P=0.016)]. Compared with the level in 2003-2008,the proportion of CTD significantly increased in 2009-2014(13.7% vs. 23.8%,χ(2)=8.598,P=0.003),along with the dicrease of the proportions of infectious diseases,neoplasms and miscellaneous diseases were decreased(all P>0.05).

CONCLUSIONSInfectious diseases(in particular,tuberculosis)remains the major cause of FUO. CTD and neoplasms also play important roles in the development of FUO. The distributions of the FUO etiologies have certain differences in terms of age,sex,duration of fever,and period.