A routine screening test for several metabolic and genetic disorders in newborns, the 'Heel-Stick' procedure, is not effective in screening for cytomegalovirus (CMV) infection, according to research published in the Journal of the American Medical Association (AMA).
The study, funded by the National Institute on Deafness and Other Communication Disorders (NIDCD), one of the National Institutes of Health, is part of a multicenter research project headed by the University of Alabama at Birmingham that is seeking to find the effective screening test for CMV infection in newborns. The standard method for detecting CMV infection in newborns is labor-intensive and not conducive to a widespread screening program.
According to the study, the heel-stick procedure involves pricking a newborn’s heel, drawing a small amount of blood, and placing the blood on filter paper to dry so that it can be analyzed for several diseases, including hypothyroidism and sickle cell disease.
To test for CMV infection, the researchers have removed the babies’ DNA from the filter paper and then used a common molecular diagnostic technique to detect whether any CMV DNA was mixed in.
The procedure, called real-time polymerase chain reaction, or PCR, uses special molecules, called primers, to seek out a tell-tale portion of CMV DNA and churn out lots of fluorescent copies of that segment so it can be easily detected. For the initial group of babies, the researchers used a single set of primers targeting one section of CMV DNA. As the study progressed, they added a second primer set targeting an additional section in hopes of increasing accuracy, or sensitivity, of the test.
The team also compared the results to the standard method of detecting CMV in newborns. CMV rapid culture is a highly effective procedure that uses saliva or urine instead of dried blood samples to make the identification. The rapid culture method is labor-intensive and requires a tissue culture facility on site, so it would be difficult to adapt this technology to a widespread screening program.
James Battey, director of the NIDCD, said: “The heel-stick test is a simple test that is already being used to screen for other diseases in newborns across the United States, so it seemed like a good candidate for a possible universal screening program for CMV. However, these findings show us that, at least with current technologies, the heel-stick test should not be used as a primary newborn screening tool for CMV.”