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- Title
Comparison of quantitative real-time PCR and direct immunofluorescence for the detection of Pneumocystis jirovecii.
- Authors
Moodley, Bhavani; Frean, John Andrew; Tempia, Stefano
- Abstract
Background: Pneumocystis pneumonia (PCP) is a serious risk for HIV-positive patients. Asymptomatic infection or colonisation with P. jirovecii has been shown to occur frequently. PCR assays frequently identify such cases, due to their high sensitivity. Quantitative real-time PCR (qPCR) gene copy number cut-off values have been suggested to differentiate colonisation and infection; these need to be standardised for routine use. We compared the results of qPCR with an immunofluorescence assay (IFA) to determine a specific cut-off value. Methods: From March 2005 through June 2009, induced sputum specimens were collected from adult patients who were clinically suspected of having PCP, at the Chris Hani Baragwanath Hospital in Gauteng, South Africa. Laboratory diagnosis of PCP was done by a conventional direct IFA and a qPCR assay. A receiver operating characteristic (ROC) analysis was performed to determine a suitable copy number cut-off value. Results: P. jirovecii was identified in 51% (156/305) and 67% (204/305) of specimens using IFA and qPCR, respectively. The cut-off value for the qPCR that best predicted the IFA results was 78 copies/5 μl (area under ROC curve 0.92). The sensitivity and specificity of qPCR using this cut-off was 94.6% and 89.1%, respectively, compared with the IFA. Discussion: The results of the ROC curve analysis indicate an excellent predictive value of the qPCR using the proposed cut-off. However, the IFA test is an imperfect gold standard and so this cut-off should not be used in isolation; clinical data should also contribute to the interpretation of the qPCR result.
- Subjects
HIV-positive persons; PNEUMOCYSTIS carinii pneumonia diagnosis; PNEUMOCYSTIS carinii pneumonia treatment; HIV infection risk factors; PNEUMOCYSTIS pneumonia
- Publication
PLoS ONE, 2017, Vol 12, Issue 7, p1
- ISSN
1932-6203
- Publication type
Article
- DOI
10.1371/journal.pone.0180589