Dried Urine Spots Detect Cytomegalovirus in Newborns

Dried urine spots (DUS) can be used to provide a simple screening tool for congenital Cytomegalovirus (CMV) infection in newborn infants.

A standardized method for CMV quantification from DUS has been developed that uses molecular technology to detect and quantify the viral load in urinary samples.

Scientists at Johns Hopkins Medical Institutions (Baltimore, MD, USA) collected and tested archived urine samples from 27 congenitally infected and 15 uninfected neonates. DNA was extracted using an automated method from urine samples placed on filter paper discs. A quantitative CMV real-time polymerase chain reaction (rt-PCR) assay was performed on the extracted DNA, spiked urine samples, and suitable control samples.

Urine samples from congenitally infected newborns and negative controls either were diluted 1:10 or applied on filter paper at the same volume. The analytical sensitivity was determined of 100% of replicates at 7,500 CMV copies/mL. The actual detection limit was 22 DNA copies/disc. DNA copy number from DUS correlated well with copy number from 1:10 diluted urine, although there was a trend for lower levels from DUS. Amplification was performed on a 7500 Real-Time PCR System (Applied Biosystems; Foster City, CA, USA).

Concentrations of CMV DNA in the 27 positive samples ranged from 4.4 to 8.8 log10 copies/mL, with a mean of 6.5 log10 copies/mL. Three samples had CMV DNA levels that were greater than the highest concentration of the spikes urine tested for measurable range calculation. This screening method could be used to detect the presence of congenital CMV infection by inserting a filter paper in the newborn's diaper and therefore for this purpose, quantification may not be necessary.

The authors concluded that the assay may provide a simple and rapid tool for CMV detection and quantification from DUS in underdeveloped or developing countries in which diagnostic capabilities for CMV are lacking. Information on CMV prevalence from resource-constrained areas is currently limited due to lack of diagnostic infrastructure. The study was published on June 1, 2012, in the journal Diagnostic Microbiology and Infectious Disease.

Related Links:
Johns Hopkins Medical Institutions
Applied Biosystems