Approach to the Adult Patient with Fever of Unknown Origin - American Family Physician

gence of human immunodeficiency virus (HIV) infection and an increasing number of patients with neutropenia. Others contend that altering the definition would not benefit the evaluation and care of patients with FUO. The four categories of potential etiology of FUO are centered on patient subtype—classic, nosocomial, immune deficient, and HIVassociated. Each group has a unique differential diagnosis based on characteristics and vulnerabilities and, therefore, a different process of evaluation (Table 1).