Laboratory diagnosis of congenital CMV infection in newborns: Impact of pre-analytic factors

Background To identify infants with congenital cytomegalovirus (cCMV) saliva polymerase chain reaction (PCR) is an ideal screening method. However, there are only few data on the influence of pre-analytic factors on the analytical sensitivity of the CMV PCR. Objectives This study aimed to evaluate the performance of different swabbing materials, transport time and initial virus concentration regarding to the efficacy of recovery of CMV-DNA. Study design Two CMV suspensions containing a high or low concentration of the laboratory strain AD 169 were prepared as test samples. Sampling was simulated by immersion of different swabs in these CMV suspensions and storing the swabs dry or in specified transport media. Transport conditions were modeled by storing the samples for defined time periods prior to DNA extraction and quantitative PCR analyses. Parallel analyses in two different laboratories allowed determination of lab to lab consistency. Results The duration of storage under the conditions analysed did not have a major effect on the recovery efficiency for the swabbing materials tested. With exception of flocked dry swabs, all tested swabbing materials demonstrated good recovery of CMV DNA. The flocked swab/eNAT system showed the best overall performance. Conclusions All tested swabbing materials (with exception of the flocked dry swabs) seem to be well suited for recovery of CMV DNA and appropriate for use for the diagnosis of cCMV infection in symptomatic cases and in general cCMV screening programs of newborns.