Risk factors for primary Pneumocystis carinii pneumonia in human immunodeficiency virus-infected adolescents and adults in the United States: reassessment of indications for chemoprophylaxis.

Risk factors for the development of a first episode of Pneumocystis carinii pneumonia (PCP) were investigated in the Adult and Adolescent Spectrum of Disease Project, a medical record review study involving longitudinal follow-up of human immunodeficiency virus-infected adults in 9 US cities. Risk factors included decreasing CD4 lymphocyte count and history of AIDS-defining illness, non-P. carinii pneumonia, oral thrush, or unexplained fever for > or = 2 days; PCP prophylaxis was protective. PCP incidence/100 person-years of observation among persons not prescribed PCP prophylaxis was higher in those with CD4 lymphocyte counts < 250 cells/microL or CD4 cell percent < 14% (8.3; 95% confidence interval [CI], 7.7-9.0) than in persons with CD4 cell counts < 200 or history of thrush or fever, which constitute current criteria for prophylaxis against PCP (5.9; 95% CI, 5.5-6.4). Because of increased efficiency in capturing persons at highest risk, CD4 cell count < 250 or CD4 cell percent < 14% should be considered as criteria for prophylaxis against first episodes of PCP.