Direct monitoring as well as sensitive diagnosis of Pneumocystis carinii pneumonia by the polymerase chain reaction on sputum samples.

In order to evaluate the usefulness of the polymerase chain reaction (PCR) for diagnosis and monitoring of Pneumocystis carinii pneumonia (PCP) in specimens obtained from non-invasive techniques, expectorated or induced sputa were collected from 30 patients who were tentatively diagnosed as having PCP and administered intravenous trimethoprim-sulfamethoxazole. Using appropriate criteria, 13 of these cases were diagnosed as having PCP, 12 cases were diagnosed of other pulmonary diseases, and five cases were omitted from the study according to the exclusion criteria. PCR was performed using primers based on the P. carinii 5S rRNA sequence. Pneumocystis carinii was detected in nine of the 13 defined cases (sensitivity of 69%) and in none of 12 non-PCP cases (specificity of 100%). In contrast, P. carinii was detected in only one case by microscopic examination using Diff-Quik stain. Therefore, the sensitivity of PCR was significantly higher than that observed with the stain (P < 0.05, chi 2 = 6.125). Sputum samples were also obtained from eight cases during the treatment. The eradication of P. carinii from the sputum as judged by PCR varied from three to 38 days (median 6.5 days) after the start of the treatment. Pneumocystis carinii shedding in sputum correlated with the time between initial clinical symptoms and initiation of the treatment (P < 0.05, r = 0.810), but not with the tension of PaO2 at the time of diagnosis. This preliminary study demonstrates that PCR allows early diagnosis of PCR and that close monitoring with non-invasive specimens can be performed by PCR.