Publications by authors named "Abner L Chan"

Objective: Recent advances in epigenetic studies continue to reveal novel mechanisms of gene regulation and control, however little is known on the role of epigenetics in sensorineural hearing loss (SNHL) in humans. We aimed to investigate the methylation patterns of two regions, one in and another in in Filipino patients with SNHL compared to hearing control individuals.

Methods: We investigated an promoter region that was previously identified as differentially methylated in children with SNHL and lead exposure.

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Many indigenous peoples are at elevated risk for otitis media, however there is limited information on hearing loss due to OM in these communities. An Indigenous Filipino community that has previously been described with an elevated prevalence of OM that is due to rare variants and a common variant underwent additional phenological testing. In this study, we describe the audiologic profiles in - and -related otitis media and the validity of otoscopy and genotyping for and variants in screening for otitis media and hearing loss.

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Hearing loss remains an important global health problem that is potentially addressed through early identification of a genetic etiology, which helps to predict outcomes of hearing rehabilitation such as cochlear implantation and also to mitigate the long-term effects of comorbidities. The identification of variants for hearing loss and detailed descriptions of clinical phenotypes in patients from various populations are needed to improve the utility of clinical genetic screening for hearing loss. Clinical and exome data from 15 children with hearing loss were reviewed.

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Objective: This study compared otoacoustic emission (OAE) and automated auditory brainstem response (AABR) in terms of concordance and cost impact for newborn hearing screening (NBHS) in the Philippine setting.

Methods: This was a prospective observational study to assess concordance between OAE and AABR involving 253 infants. Each infant underwent OAE and AABR testing.

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A genetic basis for otitis media is established, however, the role of rare variants in disease etiology is largely unknown. Previously a duplication variant within A2ML1 was identified as a significant risk factor for otitis media in an indigenous Filipino population and in US children. In this report exome and Sanger sequencing was performed using DNA samples from the indigenous Filipino population, Filipino cochlear implantees, US probands, Finnish, and Pakistani families with otitis media.

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Non-secretor status due to homozygosity for the common FUT2 variant c.461G>A (p.Trp154) is associated with either risk for autoimmune diseases or protection against viral diarrhea and HIV.

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Objective: To identify genetic and environmental risk factors for otitis media in an indigenous Filipino population.

Study Design: Cross-sectional study.

Setting: Indigenous Filipino community.

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Background: Previously rare A2ML1 variants were identified to confer otitis media susceptibility in an indigenous Filipino community and in otitis-prone US children. The goal of this study is to describe differences in the middle ear microbiome between carriers and non-carriers of an A2ML1 duplication variant that increases risk for chronic otitis media among indigenous Filipinos with poor health care access.

Methods: Ear swabs were obtained from 16 indigenous Filipino individuals with chronic otitis media, of whom 11 carry the A2ML1 duplication variant.

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A duplication variant within the middle ear-specific gene A2ML1 cosegregates with otitis media in an indigenous Filipino pedigree (LOD score = 7.5 at reduced penetrance) and lies within a founder haplotype that is also shared by 3 otitis-prone European-American and Hispanic-American children but is absent in non-otitis-prone children and >62,000 next-generation sequences. We identified seven additional A2ML1 variants in six otitis-prone children.

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The objectives of this study were to determine the agreement between the ear examination findings of the otorhinolaryngologist (trainer) and the elementary school nurse (trainee) after training with the use of a penlight and to determine the mean sound pressure level (SPL) produced by school nurses as a standard parameter for hearing screening using a 512 tuning fork after training on tuning fork testing by the otorhinolaryngologist. Training workshops in ear examination using a penlight and hearing screening using a 512 tuning fork were conducted for school nurses. Data for assessment of ear examination skills and production of SPL were collected by questionnaire and observation of performance.

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