CMV DNA detection in dried samples of urine and saliva for congenital CMV diagnosis and screening

Background - Setting up neonatal screening for congenital CMV (cCMV) infection may be worthwhile for preventing the disability caused by the infection as the identified infected infants both symptomatic and asymptomatic at birth could be enrolled in a clinical and instrumental follow up to detect the damage early and start suitable interventions promptly. Detection of CMV DNA in neonatal dried blood spots (DBS test) has proven to be a screening method simpler faster and less costly than viral isolation. However the low viral load in the blood can negatively affect the results of DBS testing. Since urine or saliva of infected babies usually contain viral loads higher than those in the blood we tested for CMV DNA samples of urine dried on paper (DUS) and of saliva dried on nylon swabs (DSS) in the aim of identifying alternative methods for cCMV diagnosis/screening. Methods- Viral DNA was searched by means of nested PCR (gB gene) in mock DUS and DSS samples, spiked with 10-fold dilutions of cell grown CMV. The same test was employed on DUS and DSS collected from 337 unselected babies (2-48 days) and 26 cCMV infected infants (14 days-6 years) as controls. Conventional urine and saliva specimens from the same subjects were tested by means of n-PCR and shell-vial assays. DBS samples of positive cases were tested to assess the nature of the infection. Results – n-PCR detected CMV DNA down to 10E3 copies/ml in mock DUS and to 10E0 copies/ml in mock DSS. Both tests identified 7 infected infants, four with congenital and three with postnatal CMV infection. Fourteen further cases were positive only in the DSS test. Testing DUS and DSS showed 100% sensitivity and 95% specificity versus testing the corresponding liquid samples. The best performances of the tests were recorded in babies within their second life week. Conclusions – Detection of viral DNA in DUS and DSS seem to be reliable methods for diagnosing cCMV infection. The ease of collection of saliva could favor the use of DSS test in screening programs when the results obtained in this study will be confirmed.