Evaluation of a real-time RT-PCR assay for the diagnosis of measles virus infections during a measles outbreak in Greece
Abstract number: 1733_940
Kokotas S., Giannaki M., Horefti E., Sgouras D., Logothetis M., Panagiotopoulos P., Georgakopoulou T., Kansouzidou A., Theodoridou M., Pangalis A., Mentis A.
Objectives: The aim of the study was to evaluate a real-time RT-PCR (RRT-PCR) for the detection of measles virus (MeV) RNA in clinical specimens collected during a measles outbreak in Greece.
Materials and Methods: Serum samples and at least one of the following samples, namely, heparinised blood, pharyngeal exudate and urine, were collected from suspected measles cases. All cases came from the measles outbreak in Greece, (October 2005August 2006). The presence of MeV-specific IgM in patient sera was analysed by a commercial indirect ELISA (Enzygnost, Dade Behring). Equivocal results were re-tested with an IF method (BIOS). Viral RNA was extracted from peripheral blood mononuclear cells (PBMC), pharyngeal exudates and urine by Qiagen Viral RNA mini kit. A quantitative RRT-PCR (Schalk et al, 2004) was utilised for the detection of MeV-RNA in all three types of samples, based upon amplification of a 413 bp amplicon in the carboxyterminal region of measles nucleoprotein gene, detected by a FRET hybridisation probe pair on the Light-Cycler.
Results: In total, 94 specimens from measles suspected cases were included in the study. In 87 patients, at least one method (serology and/or RRT-PCR) was positive for MeV infection. Of those cases, 78 were positive and 7 negative by both methods, while 9 cases were positive solely by RRT-PCR. However, in six of the 9 cases positive by RRT-PCR and negative by serology, all specimens had been collected during the first two days after onset of the rash, which might lead to false-negative results by IgM serology. After exclusion of these cases, sensitivity, specificity, positive and negative predictive values for the RRT-PCR were calculated at 100% (95% CI 95.4100.0), 70% (95% CI 34.893.3), 96% (95% CI 89.599.2) and 100% (95% CI 59.0100.0) respectively. Pharyngeal exudates yielded a higher proportion of MeV RNA detection, followed by PBMC and urine samples.
Conclusion: A higher detection rate was observed for MeV RNA in pharyngeal exudates and PBMC than for specific IgM in serum. RRT-PCR is a useful method for MeV infection confirmation and should supplement serology, especially when the specimens for MeV infections are collected within 23 days after rash onset and a second visit of the patient is not practical.
|Session name:||European Society of Clinical Microbiology and Infectious Diseases|
|Location:||ICC, Munich, Germany|
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