SEROREACTIVITY TO PNEUMOCYSTIS-CARINII IN PATIENTS WITH AIDS VERSUS OTHER IMMUNOSUPPRESSED PATIENTS

The aim was to study the humoral response to Pneumocystis carinii and its diagnostic use in patients with P. carinii pneumonia (PCP). The an tibody response was measured by indirect immunofluorescence in AIDS pa tients versus other immunosuppressed patients with 122 episodes of con firmed PCP. During the early acute stage of the pneumonia, anti-P. car inii antibodies were found in 17% of AIDS and 24% of other immunosuppr essed patients. In the second serum sample, antibodies were still foun d in 17% of the AIDS patients but in as many as 56% of the otherwise i mmunosuppressed patients. Antibodies were also found in 17% of HIV-pos itive and 15% of other immunosuppressed control patients, but only in 3% of immunocompetent controls (p < 0.001). Paired sera were available from 55 patients during 58 PCP episodes. Seroconversion or a fourfold rise in titre was detected in only 1/36 (3%) AIDS patients but in 10/ 22 (45%), (95% c.i.: 24-66%) other immunosuppressed patients (p < 0.00 1). We conclude that AIDS patients seem to have lost their ability to develop a humoral response to P. carinii during pneumonia, whereas man y other immunosuppressed patients do respond. In these patients the se rological test against P. carinii was of no diagnostic value in the ac ute phase of the infection, whereas when analysing paired sera it was a useful complement to the clinical diagnosis.