Congenital Cytomegalovirus infection: prognostic value of real-time PCR performed on dried blood spots

BACKGROUND-AIM 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. The aim of this study was to define the prognostic value of qPCR performed on dried blood spots (DBS) collected on filter paper (Guthrie-card) in congenitally CMV infected infants. 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 65 CMV infected infants was studied (mean gestational age 37.8 weeks, mean born weight 2710 g). 18/65 (27.7%) were symptomatic at birth; 8 of them (44.4%) developed sequelae. 5/47 (10.6%) asymptomatic infants developed sequelae. Nested PCR was positive in 93.8% (61/65) and qPCR in 95.4% (62/65) of all infants studied. The viral load determined by qPCR was ≥ 103 copies/mL in 68.4% of infants with symptoms at birth vs. 33.8% of those without symptoms (p < 0.005) and in 62.5% of infants who developed sequelae vs. 34.9% of those who did not (p < 0.05) (chi square 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 counselling for parents, permit careful monitoring and aid in formulation of interventional strategies.