PP1122 - Low Frequency of Genetic Testing in Children with Hearing Loss 2013-2017

Background The aim was to investigate frequency of genetic testing, results, and other aetiologies of sensorineural hearing loss in children, year 2013 - 2017, prior to implementing Massive parallel sequencing genetic testing 2018 in Lund, Sweden.

Method A retrospective review of medical records of children who received hearing aids in Lund, Sweden, year 2013 - 2017.

Results In children with sensorineural hearing loss (n=338) 27% were genetically tested resulting in 16% genetic diagnoses while 18% received non-genetic aetiologic diagnoses, and 62% remained undiagnosed.

Conclusion Genetic testing was unfrequent and minority received a genetic diagnose. The aetiology was most often unknown.

 

Summary:

Objectives

The aim was to investigate frequency of genetic testing, results, and other aetiologies of hearing loss in children, year 2013 - 2017, prior to implementing genetic testing with Massive parallel sequencing 2018 in Lund, Sweden. We hypothesized that a majority of the children underwent genetic testing but since only a few genes were tested the yield would be low.

Rationale

To investigate the result of the former praxis in investigating the aetiology of hearing loss in children is of importance to be able to evaluate the new praxis with genetic Massive parallel sequencing. In the future, if diagnosing the cause of the hearing loss it will be possible to develop treatments.

Design

In a retrospective study, medical records from 1995 until 2021 were reviewed of 375 children (0-18 years) born between 1995 and 2017. The children included received at least one hearing aid at the Department of Audiology, Lund, Sweden between January 1^st 2013 and December 31^st 2017 due to a permanent hearing impairment. After reviewing the records 37 patients were excluded, 19 since they did not receive a hearing aid, eight because their hearing impairment was not chronic, and 10 had normal hearing.

Statistical analysis

Nominal data are presented as frequencies and percentages without decimals. Ordinal and quantitative data are presented as median and interquartile range (IQR).

Results

The age distribution of the included children was 0-18 years old. Most of them had a sensorineural hearing impairment (82%) and 47% were of the female sex.

The degree of hearing impairment of the 329 patients is distributed as mild (37%), moderate (43%), severe (9%) and profound (11%). The degrees are based on the last PTA recorded.

In the study, (62%) patients did not receive a diagnosed aetiology of their hearing impairment. The aetiology was found in (36%) of the cases and in six patients (2%) the aetiology was suspected but not verified. There were 48 different aetiologies in total, where the most common one was asphyxia (n=17).

In total, 26% patients were subject to any kind of genetic test. Out of the 338 patients, 14% were tested for genetic variants in GJB2 causing hearing impairment. Eleven patients tested positive for variants causing hearing impairment and four additional patients had heterozygous variants of unknown significance (VUS).

Forty-three patients were genetically tested for other aetiologies. In four patients it was noted that they had undergone a wider genetic screening and in two of those cases (siblings), a whole genome sequencing was performed. In three out of the four cases, it led to a diagnosis. Thirteen patients tested negative.

Conclusion

Genetic testing was not common year 2013-2017 in Southern Sweden in children with sensorineural hearing loss one-fourth of the children genetically tested. One-third of the children had a documented aetiology of which half was of genetic origin and half was non-genetic. In a majority of the children, the aetiology of the hearing impairment was unknown.