Is real time PCR preferable to the direct immunofluorescence in the diagnosis of Pneumocystis jirovecii pneumonia in HIV-infected patients?

Objectives: In this study, we compared IFA and real-time PCR in bronchoalveolar lavage specimens of HIV infected patients. A total of 66 BALs from 62 HIV patients were included in the study. 30 IFA positive and 36 IFA negative specimens were tested with real-time PCR, targeting the major surface glycoprotein. We performed a retrospective analysis of the patient's medical records, compared the results of the IFA and PCR tests and analyzed costs, expenditure of time and personal expenses.

Results: All of the 30 IFA positive samples were PCR positive. 35 of 36 IFA negative probes were also negative in the PCR assay. Considering the PCR results as a binary outcome (positive/negative) sensitivity was 100%, specificity 97.2%. The patient with negative IFA and positive PCR had a clear clinical picture of PCP and responded to PCP treatment. PCR was more than twice as expensive and time-consuming as IFA. Diagnostic accuracy for PCP of PCR and IFA was comparable in HIV-infected patients, but IFA was significantly less expensive and less time-consuming. Therefore, IFA testing can continue to be used as gold standard in the diagnosis of PCP in HIV patients. However, in special cases, IFA may lack sensitivity and PCR should be added to the diagnostic armamentarium.