Objectives: We evaluated the polymerase chain reaction (PCR) detection of Pneumocystis carinii DNA in induced sputum of patients with connective tissue diseases and assessed the clinical features of patients positive for P. carinii.
Methods: Sputum was induced by nebulization in 29 in-patients with various connective tissue diseases who presented with symptoms suggestive of P. carinii pneumonia (PCP), and was examined by PCR.
Results: Detection of P. carinii DNA by PCR was significantly more sensitive than cytology; 54.5% patients were positive by PCR and only 4.5% by cytology. The prevalence of PCP was higher than previously considered and was especially high in patients receiving > 30 mg/day prednisolone with or without other immunosuppressants. P. carinii-positive patients had significant lymphocytopenia and a low serum IgG level compared with P. carinii-negative patients. P. carinii disappeared within 7-10 days after therapy with trimethoprim/sulfamethoxazole.
Conclusion: We propose that the use of PCR for detection of P. carinii using induced sputum is a useful and non-invasive method that has high sensitivity and specificity for the early diagnosis of PCP.