Molecular Assay Screens Newborns for Cytomegalovirus

A real-time polymerase-chain-reaction (rt-PCR)-based assay has been developed to test saliva specimen obtained at birth for Cytomegalovirus (CMV).

The standard assay for newborn CMV screening is rapid culture performed on saliva specimens, which cannot be automated, has been compared with rt-PCR assays performed on similar specimens.

Scientists at the University of Alabama (Birmingham, AL, USA) carried out a prospective, multicenter screening study of newborns comparing real-time PCR assays of liquid-saliva and dried-saliva specimens with rapid culture of saliva specimens obtained at birth. The infants were born at seven hospitals in the USA from June 2008 through November 2009.

A rapid-culture assay for the detection of early-antigen fluorescent foci, involving a monoclonal antibody against the major immediate early antigen of CMV, was used to detect CMV in saliva specimens. The rt-PCR protocol for dried-blood spots was performed to detect CMV DNA in saliva samples. A sample was considered positive if five or more copies per reaction were detected. The detection of CMV DNA was performed using the ABI 7500 Real-time PCR System (Applied Biosystems Inc, Foster City, CA, USA) and ABsolute QPCR Low ROX Mix (ABgene USA, Rockford, IL, USA).

A total of 177 of 34,989 infants were positive for CMV, according to at least one of the three methods. Of 17,662 newborns screened with the use of the liquid-saliva PCR assay, 17,569 were negative for CMV, and the remaining 85 infants had positive results on both culture and PCR assay. The sensitivity and specificity of the liquid-saliva PCR assay were 100% and 99.9%, respectively. Of 17,327 newborns screened by means of the dried-saliva PCR assay, 74 were positive for CMV, whereas 76 were found to be CMV-positive on rapid culture.

The authors conclude that saliva is a more reliable type of specimen than dried-blood spots for identifying congenital CMV infection by means of PCR assay and can be an effective tool for mass screening of newborns for CMV. Real-time PCR assays of both liquid-and dried-saliva specimens showed high sensitivity and specificity for detecting CMV infection and should be considered potential screening tools for CMV in newborns. The study was published online on June 2 2011, in the New England Journal of Medicine (NEJM).

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University of Alabama
Applied Biosystems Inc.
ABgene USA