A prospective multicenter study of 154 patients with FUO in twelve Turkish tertiary-care hospitals was conducted.
The mean age of the patients was 42 ± 17 years (range 17–75). Fifty-three (34.4 % ) had infectious diseases (ID), 47 (30.5 % ) had non-infectious inflammatory diseases (NIID), 22 (14.3 % ) had malignant diseases (MD), and eight (5.2 % ) had miscellaneous diseases (Mi). In 24 (15.6 % ) of the cases, the reason for high fever could not be determined despite intensive efforts. The most common ID etiologies were tuberculosis (13.6 % ) and cytomegalovirus (CMV) infection (3.2 % ). Adult Still's disease was the most common NIID (13.6 % ) and hematological malignancy was the most common MD (7.8 % ). In patients with NIID, the mean duration of reaching a definite diagnosis (37 ± 23 days) was significantly longer compared to the patients with ID (25 ± 12 days) (p = 0.007). In patients with MD, the mean duration of fever (51 ± 35 days) was longer compared to patients with ID (37 ± 38 days) (p = 0.052).
Although infection remains the most common cause of FUO, with the highest percentage for tuberculosis, non-infectious etiologies seem to have increased when compared with previous studies.