Comparison of Laboratory Methods for Detection of Pneumocystis carinii

Abstract

Detection of P. carinii is increased by the use of polymerase chain reaction (PCR), particularly on sputum samples. In this study, sputum samples obtained from 30 immunosuppressed patients with respiratory symptoms (12 HIV infected) were tested by standard cytochemical staining (Giemsa and methenamine silver), immunofluorescense (IF) staining and PCR for detection of P. carinii and the results were compared. P. carinii were detected in 4, 8, and 13 sputum samples by cytological staining, IF test and PCR, respectively. Specific amplification bands were obtained in all sputum samples which were positive by both other tests. All tests gave negative results in sputum samples obtained from 5 HIV infected asymptomatic patients. Our observations suggest that PCR results were found to be well correlated with P. carinii pneumonia (PCP) especially in non-HIV infected patients. However, PCR positivity obtained on HIV infected patients could be misleading in the diagnosis of PCP without careful clinical evaluation. Positive results obtained by Giemsa staining or IF test confirm diagnosis of PCP with high degree correlation. As a result, we suggest testing sputum samples by both PCR and IF techniques for detection of P. carinii.

Keywords

• Pneumocystis carini
• Diagnosis
• Immunofluorescense
• PCR