Congenital Cytomegalovirus Infection : Association between Dried Blood Spots Viral Load Determined by Real-Time PCR and Long-Term Outcome

BACKGROUND: Cytomegalovirus (CMV) is the leading cause of congenital infection in humans and a major cause of sensorineural hearing loss and neurologic impairment in children. Several studies have been performed to identify predictive factors of short- and long-term outcome in congenitally CMV infected infants. A high viral load, as measured by real-time quantitative polymerase chain reaction (qPCR), either in fetal amniotic fluid or in neonatal blood and urine, has been reported to correlate with future damage in the fetus and in the child. OBJECTIVE: To define the prognostic value of qPCR performed on dried blood spots (DBS) collected on filter paper (Guthrie-card) in congenitally CMV infected infants. DESIGN/METHODS: CMV infected infants were followed-up for at least 3 years: virologic tests, clinical, psychometric, ophthalmologic and audiologic evaluations were performed at birth, at 3-6-12-18 months of age, and annually thereafter. Guthrie-cards performed in the first days of life for neonatal screening of genetic and metabolic disorders were subsequently obtained from the regional screening laboratory for all the study subjects and tested for CMV by qualitative and quantitative PCR (nested and qPCR). RESULTS: A cohort of 55 CMV infected infants were studied (mean GA 37,4 wks, mean BW 2750 g). 16/55 (29%) were symptomatic at birth; 7 of them (43,7%) developed sequelae. 4/39 (10,2%) asymptomatic infants developed sequelae. Nested PCR was positive in 98,2% (54/55) and qPCR in 94,5% (52/55) of all infants studied. The viral load determined by qPCR was ≥ 103 copies/mL in 66,1% of infants with symptoms at birth vs 34,9% of those without symptoms (p < 0,005) and in 61,5% of infants who developed sequelae vs 34,2% of those who did not (p < 0,05) (χ2 test). CONCLUSIONS: DBS test using real-time qPCR seems to be a useful method to identify infants at high risk of sequelae. The ability to identify children who are at increased risk for neurologic impairment should provide a basis for more timely and appropriate counseling for parents, permit careful monitoring and aid in formulation of interventional strategies