A Controlled Trial of Aerosolized Pentamidine or Trimethoprim–Sulfamethoxazole as Primary Prophylaxis against Pneumocystis carinii Pneumonia in Patients with Human Immunodeficiency Virus Infection

PNEUMOCYSTIS CARINII pneumonia (PCP) is the most common serious opportunistic infection among patients with human immunodeficiency virus (HIV) infection, occurring at some point in at least 85 percent of patients. 1 2 3 The case fatality rate ranges from 5 to 40 percent and is highest among patients with acute respiratory failure. 2 3 4 5 6 Masur et al. 7 and other authors 3 , 8 , 9 found in retrospective studies that HIV-infected patients with peripheral-blood CD4 lymphocyte concentrations of more than 350 per cubic millimeter (0.35×10 9 per liter) did not have PCP, whereas the incidence increased as the CD4 cell count declined below 200 per cubic millimeter (0.2×10 9 per liter). The . . .