ObjectiveTo evaluate alterations in lung function during the course of HIV infection.DesignTotal lung capacity (TLC), the ratio of forced expiratory volume in one second to vital capacity (FEV1/VC), the carbon monoxide transfer factor (TLCO) and the alveolar-arterial oxygen gradient [Δ (A-a)O2] were determined in this retrospective study.PatientsPulmonary function tests (PFT) were performed on 331 patients at various stages of HIV infection. Patients with a history of intravenous drug use or Kaposi's sarcoma were excluded.ResultsNo significant differences were observed between the results for asymptomatic patients and those with AIDS-related complex (ARC). TLC, Δ(A-a)O2and TLCO were greatly altered in patients with acutePneumocystis cariniipneumonia (PCP). No significant differences were observed in the TLC, Δ(A-a)O2or TLCO results between AIDS patients with no history of PCP and those with a history of a single episode of PCP. TLCO was significantly lower (P< 0.001) in AIDS patients with one previous episode of PCP than in the patients with ARC. Interestingly, both TLC and TLCO were significantly lower in the AIDS patients with no history of PCP than in the patients with ARC. Follow-up of 28 patients at different stages of HIV infection confirmed the alteration of PFT results in the late stages.ConclusionsThe reasons for alterations in PFT results in PCP-free AIDS patients remain to be determined. Our findings suggest that PFT can provide valuable information throughout the course of HIV infection, particularly with regard to the indication for bronchoalveolar lavage.