Overview
Real-time RT-PCR (RT-qPCR) may be used to identify and confirm suspected measles and rubella cases. Many of the laboratories in the GMRLN are equipped and trained to detect measles- and rubella-specific RNA directly from clinical specimens by RT-qPCR , which is much more sensitive than conventional RT-PCR. Protocols for performing RT-qPCR for the laboratory confirmation of measles or rubella infection have been developed and evaluated over many years and the assays continue to be improved.
When appropriate virologic specimens are available for testing, virus-specific RNA detection by RT-qPCR for case confirmation is performed in many laboratories in combination with serologic or oral fluid testing for virus-specific IgM. This approach has greatly improved the ability of the laboratories to provide timely confirmation of measles and rubella cases [1-4]. In addition, detection of viral RNA can provide a more reliable method for case confirmation than testing for IgM in low-prevalence settings, particularly in post-elimination settings [5].
Compared to conventional RT-PCR assays, real-time RT-PCR offers improved analytical sensitivity and the capacity for higher throughput without the need for post-amplification processing. However, the incorporation of adequate assay controls and the maintenance of physical separation of activities that reduce the risk of contamination are crucial. While this chapter provides guidance and recommendations for the diagnostic use of real-time RT-PCR, each laboratory in the GMRLN should work with their national surveillance program and regional laboratory coordinator before incorporating RT-PCR as a tool for routine case confirmation.
Note: The abbreviation, RT-PCR, may be used herein to refer to both conventional (endpoint) reverse transcription PCR and to real-time (kinetic) RT-PCR, when describing characteristics of RT-PCR in general. Because real-time RT-PCR can be used for quantification of RNA in clinical specimens, real-time RT-PCR it is sometimes referred to as quantitative real-time RT-PCR and abbreviated as RT-qPCR.