Criteria for Diagnosis of Fever of Unknown Origin (FUO)

Number of times that the body temperature has been documented to be > 38.3°C

Number of weeks that the patient has been febrile

Number of outpatient visits made to workup the patient's fever

Number of days in the hospital used to workup the patient's fever

Has the cause for the fever been found after a thorough workup?

Is the physician evaluating the patient experienced in evaluating febrile illnesses?