Test code: 37010

Clinical use

• Diagnose or screen for congenital cytomegalovirus (CMV) infection in newborns

Clinical background

Congenital CMV infection is the leading infectious cause of birth defects in the United States.¹ Overall prevalence of congenital CMV infection is approximately 0.5% but Black newborns are almost twice as likely to be affected than the general population.² Congenital CMV infection can lead to long-term neurological and developmental sequelae, even death.² Hearing loss is the most common sequela of congenital CMV infection.²

In symptomatic newborns, early diagnosis and antiviral therapy improve outcomes.² However, signs and symptoms (eg, jaundice, petechiae, hepatosplenomegaly, microcephaly, retinitis, intracerebral calcifications) are nonspecific and only present in 10% of newborn with CMV infection.^1,2 Laboratory testing is required for diagnosis and involves direct detection of the virus or viral DNA from saliva, urine, blood, or cerebrospinal fluid (CSF) within 21 days of birth.^1,2 Postnatal infection, which does not typically cause severe disease, cannot be ruled out beyond 21 days because saliva CMV shedding in patients with congenital CMV infection can last until 20 months of age.^1–3 

In asymptomatic newborns, detecting congenital CMV infection informs decisions on appropriate surveillance of hearing sensitivity and early intervention of hearing loss.^2,4 Different screening approaches are used to identify congenital CMV infection in the United States.^2,5,6 Newborns who fail hearing screening need laboratory testing to screen for congenital CMV. However, hearing-targeted CMV screens may miss about 40% of newborns for whom hearing loss is not detectable in the first month.² Consequently, universal newborn screening for congenital CMV infection is recommended by the American Cochlear Implant Alliance, the American Academy of Otolaryngology–Head and Neck Surgery, and the National CMV Foundation.⁴ However, the optimal specimen for screening (saliva, urine, or dried blood spot [DBS]) remains an active research question.^4–6

According to the Centers for Disease Control and Prevention, polymerase chain reaction (PCR) testing using saliva specimens is preferred for screening and diagnosing congenital CMV infection.¹ The diagnostic accuracy of salivary PCR is high for both general newborns (sensitivity 96.5%, specificity 99.9%) and newborns at high risk for congenital CMV infection (sensitivity 94.4%, specificity 95.7%).⁷ However, false-positive results can occur when CMV sheds in breast milk from a maternal infection. A urine PCR test is recommended to confirm positive results of saliva PCR.^2,6 

Quest Diagnostics offers the Cytomegalovirus DNA, Qualitative Real-Time PCR, Saliva test for screening for and diagnosing congenital CMV among newborns (test code 37010). Quest also offers a qualitative PCR test to detect CMV in urine (test code 10601). 

Interpretive information

A “detected” result on a specimen collected is consistent with congenital CMV infection. Confirmation of positive results with a CMV PCR test on a urine specimen is needed.^2,6 

A “not detected” result is consistent with the absence of CMV infection. High concentrations of lipids are known to interfere with this assay and may cause false-negative results.