Molecular analysis in diagnostic procedure of hearing impairment in newborns

To determine the proportion of newborns diagnosed with hearing impairment through the hearing impairment screening program in newborns, and the frequency of 35delG/GJB2 mutation as a cause of hearing impairment. The results of the study imply the integration of the mutation analysis in the neonatal screening program.

Evoked otoacustic emission (E-OAE) screening program was performed among 6019 newborns at the Department of Obstetrics and Gynaecology, Rijeka University Hospital Center, between October 2002 and December 2004. Newborns diagnosed with hearing impairment were re-examined after three weeks and if abnormal responses persisted, the diagnosis was evaluated by auditory brainstem evoked response (ABER) testing. Children with confirmed diagnosis were examined by allele-specific polymerase chain reaction to identify the presence of 35delG/GJB2 mutation.

After the first and second stage of screening, 86 newborns were suspect of having hearing impairment. ABER confirmed the diagnosis of hearing impairment in 14 children. Molecular analysis revealed 35delG/GJB2 mutation in 2 of 8 children analyzed. The mutation was homozygous in one, and heterozygous in the other child.

Neonatal hearing impairment screening is useful for early diagnosis of hearing impairment. It should be complemented with the 35delG/GJB2 mutation analysis, because the identification of the mutation and the etiologic diagnosis might improve the medical treatment and genetic counselling of patients and families with hearing impairment.