Congenital cytomegalovirus is the most common non-genetic cause of childhood sensorineural hearing loss, affecting roughly 1 in 200 newborns globally — yet most cases are missed at birth because universal screening protocols remain absent in nearly every healthcare system. A method that could piggyback on the routine heel-prick blood collection already performed on virtually every newborn would be transformative if it proved accurate enough. This systematic review scrutinizes exactly that promise.
Pooling nine studies with individual sample sizes ranging from 1,174 to more than 551,000 dried blood spot (DBS) specimens, the review evaluated DBS-based PCR detection of congenital CMV against confirmatory saliva or urine PCR performed within 21 days of life. Specificity was impressively consistent, clustering between 99.9% and 100%, meaning false-positive rates are negligible. The critical weakness lies in sensitivity, which varied enormously — from just 28.3% to 79.3% across included studies. Positive predictive value ranged from 39% to 100%, and the pooled negative predictive value approached but did not reach a threshold that would allow DBS alone to confidently rule out infection.
This variability is the central clinical problem. A screening tool that misses between 21% and 72% of truly infected newborns cannot function as a reliable population-level gatekeeper, particularly when early antiviral treatment with valganciclovir has demonstrated meaningful reductions in hearing deterioration if initiated within the first month of life. The sensitivity ceiling appears tied to viral load: CMV DNA degrades on filter paper over time and is diluted by the small blood volume collected, making the DBS matrix fundamentally less sensitive than fresh saliva or urine.
The broader research landscape already includes saliva PCR as a low-cost, high-sensitivity alternative, but DBS retains one unique advantage — samples are routinely archived, enabling retrospective diagnosis. As an adjunct rather than a primary screen, DBS may still have a role in investigating children who later present with unexplained hearing loss. For now, this systematic review confirms that DBS-only universal newborn CMV screening would leave too many infected infants undetected to justify adoption without methodological improvements or combination strategies.