Universal Dried Blood Spot Screening for Congenital Cytomegalovirus: A Slovenian National Implementation Pilot

Congenital cytomegalovirus infection (cCMV) is the most common congenital infection and an important cause of sensorineural hearing loss and neurodevelopmental impairment, yet many affected infants remain undetected under selective screening approaches. We conducted a prospective national pilot study to evaluate the feasibility and diagnostic yield of universal dried blood spot (DBS)-based screening for cCMV within the Slovenian newborn screening program. DBS samples collected within 72 h of life were tested by polymerase chain reaction (PCR), and screen-positive newborns underwent confirmatory urine PCR within 21 days together with standardized clinical evaluation. Among 5556 screened newborns, 13 (0.23%) screened positive and cCMV was confirmed in 10, corresponding to a lower-bound birth prevalence of 1.80 per 1000 live births (95% confidence interval, 0.98–3.31), because confirmatory testing was limited to DBS-positive newborns. None of the confirmed cases were clinically suspected at birth, and all passed newborn hearing screening. Six infants met protocol-defined criteria for symptomatic cCMV and received valganciclovir. Historical registry-based clinical case ascertainment in Slovenia corresponded to 0.09 detected cases per 1000 live births. These findings demonstrate the feasibility of universal DBS-based cCMV screening within an established newborn screening infrastructure and suggest substantial under-ascertainment under selective clinical detection pathways.