Salivary PCR assay as screening tool for cytomegalovirus infection in newborns

A comparison of real-time polymerase-chain-reaction (PCR)-based testing of liquid and dried-saliva specimens with standard rapid culture of saliva specimens obtained at birth showed that PCR assays of both types of saliva specimens have high sensitivity and specificity for detecting congenital cytomegalovirus (CMV) infection.

Investigators screened almost 35,000 infants, born at 7 US hospitals during a 17-month period, using either liquid- or dried-salivary specimens in addition to rapid CMV culture. Compared with standard rapid culture, the sensitivity and specificity of the liquid-saliva PCR assay used to screen about 17,570 newborns were 100% and 99.9%, respectively; positive and negative predictive values were 91.4% and 100%, respectively. On the basis of the results of screening a similar number of newborns with the dried-saliva PCR assay, the sensitivity and specificity of this test were 97.4% and 99.9%, respectively; positive and negative predictive values of 90.2% and 99.9%, respectively.

Investigators also performed all 3 screening methods on salivary specimens obtained from 5,276 newborns. Agreement was 100% between the results of the liquid-saliva and dried-saliva PCR assays; further, both types of PCR assay confirmed the CMV-positive status of all infants with positive rapid culture results (Boppana SB, et al. N Engl J Med. 2011;364[22]:2111-2118).

The argument for CMV screening at birth is that CMV is a common cause of hearing loss that often develops after the newborn period. Newborn testing would allow for targeted monitoring and early intervention in babies who develop hearing loss secondary to congenital CMV. Previous studies of CMV screening using dried blood spots have shown poor sensitivity. Urine PCR testing may be better but is too inconvenient for universal use. The methods described here, particularly the dried-saliva technique, may represent the easy, accurate screens that researchers have been looking for.
-Michael Burke, MD