The importance of DBS samples testing for the diagnosis of congenital CMV infection in children with hearing loss

INTRODUCTION Congenital Cytomegalovirus (cCMV) is the leading cause of non-genetic hearing loss in childhood but a universal cCMV screening is currently absent in Italy. After the first 3 weeks of life, polymerase chain reaction (PCR) analysis of dried blood spot (DBS) samples on the Guthrie card -collected within three days from the birth-, is probably the only way to distinguish congenital from acquired CMV infection [1]. We estimated the rate of cCMV infections in children with hearing loss identified through the universal newborn hearing screening (UNHS) and then confirmed by the third-level referral audiological center of the "Fondazione IRCCS Ca' Granda, Ospedale Maggiore Policlinico" in Milan (Italy) [1]. METHODS DBS samples of children who received a diagnosis of sensorineural hearing loss during seven consecutive years (2014-2020) were tested for cCMV-DNA at the Virological Laboratories of the Department of Biomedical Sciences for Health, University of Milan [1]. RESULTS Among all children who received a diagnosis of sensorineural hearing loss (N=111), 7.2% (N=8) resulted positive for cCMV; half of these children experienced bilateral hearing loss, ranging from moderate (N=1) to profound (N=3), while the remaining half had unilateral hearing loss, ranging from mild (N=1) to severe (N=1) and profound (N=1). Overall, children with cCMV had a higher rate of profound hearing loss (50% vs 35%). CONCLUSIONS In absence of a universal cCMV screening, DBS samples represent a “universal newborns biobank” that allow an early and retrospective identification of cCMV infection, being of paramount importance for promoting specific diagnostic assessment and rehabilitative procedures to prevent immediate and long-term complications, such as hearing loss. Therefore, PCR analysis of DBS samples on the Guthrie card (if still stored) should be performed to all children with a diagnosis of hearing loss, in order to rule out congenital cCMV. References 1) Pellegrinelli L, Galli C, Primache V, Alde' M, Fagnani E, Di Berardino F, Zanetti D, Pariani E, Ambrosetti U, Binda S. Diagnosis of congenital CMV infection via DBS samples testing and neonatal hearing screening: an observational study in Italy. BMC Infect Dis. 2019;19(1):652. Published 2019 Jul 22. doi:10.1186/s12879-019-4296-5