9 Pyrexia of unknown origin (PUO)

Abstract

General review definition divides PUO as classical, nosocomial, HIV-related and immunosuppression-related [1]. For HIV infection, pyrexia of unknown origin (PUO) identifies a pattern of fever with temperature higher than 38.3 1C on several occasions over more than 4 weeks for outpatients, or more than 3 days duration in hospital, in which the diagnosis remains uncertain after an initial diagnostic work-up, including at least 2 days of incubation of microbiological cultures [2]. It is a common clinical manifestation in HIV-seropositive patients with severe immunosuppression and probability of an infection-related aetiology for PUO in HIV infection increases with CD4 decline, i.e. greater risk if CD4 count o50 cells/mL than o100 cells/mL than 4200 cells/mL [3]. Fever is rarely the result of the effects of HIV itself and investigation of a specific cause should be actively pursued [4] (level of evidence IV).