UC Irvine

Fever of undetermined ongm (FUO) in patients with neoplastic diseases is a major clinical challenge, requiring a great deal of the physician's time and expertise, as well as incurring much medical expense. The initial definition of FUO by Petersdorf and Beeson1 in 1961 is generally accepted. The term has been used only in reference to patients who have a temperature elevation above 101 ° F for at least 3 weeks and for whom a diagnosis cannot be established during at least 1 week of an in-hospital investigation. These rigid criteria usually have excluded many identifiable fevers from the FUO category. In addition, over the past two decades the advancement of medical knowledge and technology has further diminished the number of genuine FUOs. Nevertheless, more difficult cases of FUO are often encountered now, especially in immunocompromised patients after chemotherapy.