Evolution of the incidence and aetiology of fever of unknown origin (FUO), and survival in HIV-infected patients after HAART (Highly Active Antiretroviral Therapy).

Background: Fever of unknown origin (FUO) is common among HIV-infected patients with a CD4+ T-lymphocyte cell count below 200 cells/ml. The use of HAART has transformed the evolution of AIDS and related diseases.
Design and Method: Case-control study, nested on a historical cohort of 3777 HIV-infected patients who were attended at "12 de Octubre" University Hospital in Madrid, Spain, between 1994 and 2000.
Results: 276 FUO episodes were recorded, 58 of which occurred in patients receiving HAART. The significant decrease on the accumulated FUO incidence along the study period of 7.3 episodes per 100 HIV-infected patients after 1997 corresponded with the introduction of HAART. FUO was more frequent in patients who did not receive HAART. The aetiological spectrum of FUO was transformed by the introduction of HAART: the incidence of tuberculosis decreased while that of leishmaniasis increased. The four year survival in the non-FUO group increased when compared to that of patients who had had FUO. Similarly, this four year survival increased in patients who received HAART at the time of FUO versus those not receiving it.
Conclusions: Our results confirm that the incidence of FUO has significantly decreased with the introduction of HAART. HAART has also transformed the aetiological spectrum related to FUO considerably. The most frequent cause of FUO in non-HAART patients on this study was the disseminated infection by Mycobacterium avium intracellulare (MAI), followed by tuberculosis, while leishmaniasis was its most common cause in patients receiving HAART. Survival decreased in patients who developed FUO; however, patients who received HAART at the time of FUO had longer survival than patients who did not.
(2009 European Federation of Internal Medicine.)