Visualisation of Multiple Tight Junctional Complexes in Human Airway Epithelial Cells.

BACKGROUND: Apically located tight junctions in airway epithelium perform a fundamental role in controlling macromolecule migration through paracellular spaces. Alterations in their expression may lead to disruptions in barrier integrity, which subsequently facilitates entry of potential bacterial and other pathogens into the host. Furthermore, there is emerging evidence that the barrier integrity of the airway in certain airway inflammatory diseases may be altered. However, there is little consensus on the way this is assessed and measured and the type of cells used to achieve this. METHODS: Here, we assessed four fixation methods including; (i) 4% (v/v) paraformaldehyde; (ii) 100% methanol; (iii) acetone or; (iv) 1:1 methanol: acetone. Pre-extraction with Triton X-100 was also performed and assessed on cells prior to fixation with either methanol or paraformaldehyde. Cells were also permeabilized with 0.1% (v/v) Saponin in 1× TBS following fixation and subsequently stained for tight junction proteins. Confocal microscopy was then used to visualise, compare and evaluate staining intensity of the tight junctional complexes in order to determine a standardised workflow of reproducible staining. RESULTS: Positive staining was observed following methanol fixation for claudin-1 and ZO-1 tight junction proteins but no staining was detected for occludin in 16HBE14o- cells. Combinatorial fixation with methanol and acetone also produced consistent positive staining for both occludin and ZO-1 tight junction proteins in these cells. When assessed using primary cells cultured at air-liquid interface, similar positive staining for claudin-1 and ZO-1 was observed following methanol fixation, while similar positive staining for occludin and ZO-1 was observed following the same combinatorial fixation with methanol and acetone. CONCLUSIONS: The present study demonstrates the importance of a personalised approach to optimise staining for the visualisation of different tight junction proteins. Of significance, the workflow, once optimised, can readily be translated into primary airway epithelial cell air-liquid interface cultures where it can be used to assess barrier integrity in chronic lung diseases.

Ear, nose and throat surgery: All you need to know about the surgical approach to the management of middle-ear effusions in Australian Indigenous and non-Indigenous children.

Otitis media (OM) is a common condition in Australia. It represents a spectrum of diseases from otitis media with effusion (OME) to chronic suppurative otitis media. For all the OM diagnoses, Australian Indigenous children have higher rates of early onset, severe and persistent disease. OME is the most common form of OM and often occurs after an upper respiratory tract infection. It can be difficult to diagnose (and often goes unrecognised). Hearing loss is the most important complication. The middle-ear effusion impedes the movement of the tympanic membrane and causes a conductive hearing loss of around 25 dB. Around 20% will have a hearing loss exceeding 35 dB. Children with early onset, persistent, bilateral OME and hearing loss (or speech delay) are most likely to benefit from interventions. However, the impact of all the effective treatment options is modest. Giving advice about effective communication strategies for young children is always appropriate. The best evidence from randomised trials supports not using antihistamines and/or decongestants, considering a trial of antibiotics and referral for tympanostomy tubes. Despite the availability of evidence-based guidelines, giving advice about treatment is a challenge because recommendations vary according to condition, age, risk of complications and parental preference. While most children with OME can be effectively managed in primary care, we need to get children who meet the criteria for simple ear, nose and throat procedures that improve hearing on to ear, nose and throat surgery waiting lists. Long delays in hearing support may contribute to life-long social and economic disadvantage.

Alpha-1 Antitrypsin Mitigates the Inhibition of Airway Epithelial Cell Repair by Neutrophil Elastase.

Neutrophil elastase (NE) activity is associated with many destructive lung diseases and is a predictor for structural lung damage in early cystic fibrosis (CF), which suggests normal maintenance of airway epithelium is prevented by uninhibited NE. However, limited data exist on how the NE activity in airways of very young children with CF affects function of the epithelia. The aim of this study was to determine if NE activity could inhibit epithelial homeostasis and repair and whether any functional effect was reversible by antiprotease alpha-1 antitrypsin (α1AT) treatment. Viability, inflammation, apoptosis, and proliferation were assessed in healthy non-CF and CF pediatric primary airway epithelial cells (pAECnon-CF and pAECCF, respectively) during exposure to physiologically relevant NE. The effect of NE activity on pAECCF wound repair was also assessed. We report that viability after 48 hours was significantly decreased by 100 nM NE in pAECnon-CF and pAECCF owing to rapid cellular detachment that was accompanied by inflammatory cytokine release. Furthermore, both phenotypes initiated an apoptotic response to 100 nM NE, whereas ≥ 50 nM NE activity significantly inhibited the proliferative capacity of cultures. Similar concentrations of NE also significantly inhibited wound repair of pAECCF, but this effect was reversed by the addition of α1AT. Collectively, our results demonstrate free NE activity is deleterious for epithelial homeostasis and support the hypothesis that proteases in the airway contribute directly to CF structural lung disease. Our results also highlight the need to investigate antiprotease therapies in early CF disease in more detail.

Reduced transforming growth factor ß1 (TGF-ß1) in the repair of airway epithelial cells of children with asthma.

BACKGROUND AND OBJECTIVE: Evidence into the role of TGF-ß1 in airway epithelial repair in asthma is still controversial. This study tested the hypothesis that the reduced TGF-ß1 levels previously observed in paediatric asthmatic airway epithelial cells directly contribute to the dysregulated repair seen in these cells. METHODS: Primary airway epithelial cells (pAEC) from children with asthma (n = 16) and non-asthmatic subjects (n = 20) were isolated, and subcultured for investigation of TGF-ß1 gene and protein via quantitative polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Expression of other associated genes such as integrins αvß6, αvß8 and MT1-MMP were also tested. Small interfering RNA (siRNA) was employed to assess the role of TGF-ß1 during wound repair. RESULTS: TGF-ß1 gene and protein expression were significantly downregulated in asthmatic pAEC over the course of repair, compared with cells from non-asthmatic children. Messenger RNA (mRNA) expression of TGF-ß1 was also directly implicated in non-asthmatic and asthmatic pAEC proliferation over their quiescent counterparts. Small interfering RNA-mediated knockdown of TGF-ß1 compromised repair in non-asthmatic pAEC and exacerbated the dysregulated repair seen in asthmatic pAEC. Expression of major TGF-ß1 activators of epithelial cells, integrin αvß6 and αvß8 was also measured and there was no difference in αvß6 gene expression between the two cohorts. Although integrin αvß8 gene expression was significantly higher in asthmatic pAEC, the expression of MT1-MMP (MMP14) which facilitates the αvß8 mediated TGF-ß1 activation was significantly downregulated. CONCLUSION: Our data has highlighted the importance of TGF-ß1 in pAEC wound repair in vitro. The significantly lower levels seen in asthmatic pAEC subsequently contributes to the dysregulated repair observed in these cells.

Determinants of culture success in an airway epithelium sampling program of young children with cystic fibrosis.

AIM OF THE STUDY: The bronchial brushing technique presents an opportunity to establish a gold standard in vitro model of Cystic Fibrosis (CF) airway disease. However, unique obstacles exist when establishing CF airway epithelial cells (pAECCF). We aimed to identify determinants of culture success through retrospective analysis of a program of routinely brushing children with CF. MATERIALS AND METHODS: Anaesthetised children (CF and non-CF) had airway samples taken which were immediately processed for cell culture. Airway data for the CF cohort was obtained from clinical records and the AREST CF database. RESULTS: Of 260 brushings processed for culture, 114 (43.8%) pAECCF successfully cultured to passage one (P1) and 63 (24.2% of total) progressed to passage two (P2). However, >80% of non-CF specimens (pAECnon-CF) cultured to P2 from similar cell numbers. Within the CF cohort, specimens successfully cultured to P2 had a higher initial cell count and lower proportion of severe CF mutation phenotype than those that did not proliferate beyond initial seeding. Elevated airway IL-8 concentration was also negatively associated with culture establishment. Contamination by opportunistic pathogens was observed in 81 (31.2% of total) cultures and brushings from children with lower respiratory tract infections were more likely to co-culture contaminating flora. CONCLUSIONS: Lower passage rates of pAECCF cultures uniquely contrasts with pAECnon-CF despite similar cell numbers. An equivalent establishment rate of CF nasal epithelium reported elsewhere, significant associations to CFTR mutation phenotype, elevated airway IL-8 and opportunistic pathogens all suggest this is likely related to the CF disease milieu.

Dysregulated Notch Signaling in the Airway Epithelium of Children with Wheeze.

The airway epithelium of children with wheeze is characterized by defective repair that contributes to disease pathobiology. Dysregulation of developmental processes controlled by Notch has been identified in chronic asthma. However, its role in airway epithelial cells of young children with wheeze, particularly during repair, is yet to be determined. We hypothesized that Notch is dysregulated in primary airway epithelial cells (pAEC) of children with wheeze contributing to defective repair. This study investigated transcriptional and protein expression and function of Notch in pAEC isolated from children with and without wheeze. Primary AEC of children with and without wheeze were found to express all known Notch receptors and ligands, although pAEC from children with wheeze expressed significantly lower NOTCH2 (10-fold, p = 0.004) and higher JAG1 (3.5-fold, p = 0.002) mRNA levels. These dysregulations were maintained in vitro and cultures from children with wheeze displayed altered kinetics of both NOTCH2 and JAG1 expression during repair. Following Notch signaling inhibition, pAEC from children without wheeze failed to repair (wound closure rate of 76.9 ± 3.2%). Overexpression of NOTCH2 in pAEC from children with wheeze failed to rescue epithelial repair following wounding. This study illustrates the involvement of the Notch pathway in airway epithelial wound repair in health and disease, where its dysregulation may contribute to asthma development.

Ivacaftor or lumacaftor/ivacaftor treatment does not alter the core CF airway epithelial gene response to rhinovirus.

BACKGROUND: Aberrant responses by the cystic fibrosis airway epithelium during viral infection may underly the clinical observations. Whether CFTR modulators affect antiviral responses by CF epithelia is presently unknown. We tested the hypothesis that treatment of CF epithelial cells with ivacaftor (Iva) or ivacaftor/lumacaftor (Iva/Lum) would improve control of rhinovirus infection. METHODS: Nineteen CF epithelial cultures (10 homozygous for p.Phe508del as CFTR Class 2, 9 p.Phe508del/p.Gly551Asp as Class 3) were infected with rhinovirus 1B at multiplicity of infection 12 for 24 h. Culture RNA and supernatants were harvested to assess gene and protein expression respectively. RESULTS: RNA-seq analysis comparing rhinovirus infected cultures to control identified 796 and 629 differentially expressed genes for Class 2 and Class 3, respectively. This gene response was highly conserved when cells were treated with CFTR modulators and were predicted to be driven by the same interferon-pathway transcriptional regulators (IFNA, IFNL1, IFNG, IRF7, STAT1). Direct comparisons between treated and untreated infected cultures did not yield any differentially expressed genes for Class 3 and only 68 genes for Class 2. Changes were predominantly related to regulators of lipid metabolism and inflammation, aspects of epithelial biology known to be dysregulated in CF. In addition, CFTR modulators did not affect viral copy number, or levels of pro-inflammatory cytokines produced post-infection. CONCLUSIONS: Though long-term clinical data is not yet available, results presented here suggest that first generation CFTR modulators do not interfere with core airway epithelial responses to rhinovirus infection. Future work should investigate the latest triple modulation therapies.

Aberrant cell migration contributes to defective airway epithelial repair in childhood wheeze.

Abnormal wound repair has been observed in the airway epithelium of patients with chronic respiratory diseases, including asthma. Therapies focusing on repairing vulnerable airways, particularly in early life, present a potentially novel treatment strategy. We report defective lower airway epithelial cell repair to strongly associate with common pre-school-aged and school-aged wheezing phenotypes, characterized by aberrant migration patterns and reduced integrin α5ß1 expression. Next generation sequencing identified the PI3K/Akt pathway as the top upstream transcriptional regulator of integrin α5ß1, where Akt activation enhanced repair and integrin α5ß1 expression in primary cultures from children with wheeze. Conversely, inhibition of PI3K/Akt signaling in primary cultures from children without wheeze reduced α5ß1 expression and attenuated repair. Importantly, the FDA-approved drug celecoxib - and its non-COX2-inhibiting analogue, dimethyl-celecoxib - stimulated the PI3K/Akt-integrin α5ß1 axis and restored airway epithelial repair in cells from children with wheeze. When compared with published clinical data sets, the identified transcriptomic signature was also associated with viral-induced wheeze exacerbations highlighting the clinical potential of such therapy. Collectively, these results identify airway epithelial restitution via targeting the PI3K-integrin α5ß1 axis as a potentially novel therapeutic avenue for childhood wheeze and asthma. We propose that the next step in the therapeutic development process should be a proof-of-concept clinical trial, since relevant animal models to test the crucial underlying premise are unavailable.

Australian Aboriginal children have higher hospitalization rates for otitis media but lower surgical procedures than non-Aboriginal children: A record linkage population-based cohort study.

INTRODUCTION: Otitis media (OM) is one of the most common infectious diseases affecting children globally and the most common reason for antibiotic prescription and paediatric surgery. Australian Aboriginal children have higher rates of OM than non-Aboriginal children; however, there are no data comparing OM hospitalization rates between them at the population level. We report temporal trends for OM hospitalizations and in-hospital tympanostomy tube insertion (TTI) in a cohort of 469,589 Western Australian children born between 1996 and 2012. MATERIALS AND METHODS: We used the International Classification of Diseases codes version 10 to identify hospitalizations for OM or TTI recorded as a surgical procedure. Using age-specific population denominators, we calculated hospitalization rates per 1,000 child-years by age, year and level of socio-economic deprivation. RESULTS: There were 534,674 hospitalizations among 221,588 children hospitalized at least once before age 15 years. Aboriginal children had higher hospitalization rates for OM than non-Aboriginal children (23.3/1,000 [95% Confidence Interval (CI) 22.8,24.0] vs 2.4/1,000 [95% CI 2.3,2.4] child-years) with no change in disparity over time. Conversely non-Aboriginal children had higher rates of TTI than Aboriginal children (13.5 [95% CI 13.2,13.8] vs 10.1 [95% CI 8.9,11.4]). Children from lower socio-economic backgrounds had higher OM hospitalization rates than those from higher socio-economic backgrounds, although for Aboriginal children hospitalization rates were not statistically different across all levels of socio-economic disadvantage. Hospitalizations for TTI among non-Aboriginal children were more common among those from higher socio-economic backgrounds. This was also true for Aboriginal children; however, the difference was not statistically significant. There was a decline in OM hospitalization rates between 1998 and 2005 and remained stable thereafter. CONCLUSION: Aboriginal children and children from lower socio-economic backgrounds were over-represented with OM-related hospitalizations but had fewer TTIs. Despite a decrease in OM and TTI hospitalization rates during the first half of the study for all groups, the disparity between Aboriginal and non-Aboriginal children and between those of differing socioeconomic deprivation remained.

Adenoidectomy for middle ear effusion: a study of 50,000 children over 24 years.

OBJECTIVE: To compare the incidence and outcomes of myringotomy plus ventilation tube insertion (MVTI) alone and that concurrent with pharyngeal surgery (adenoidectomy, adenotonsillectomy, or tonsillectomy) at a population level. STUDY DESIGN: Observational, retrospective, population-based study using hospital administrative data. METHODS: All hospital morbidity information was obtained for children who underwent a first MVTI procedure while less than 10 years of age in any Western Australian hospital from 1981 to 2004. Further MVTI procedures and additional pharyngeal surgery were subsequently identified for each child. RESULTS: There were 51,373 children less than 10 years of age who underwent at least one MVTI procedure from 1981 to 2004. Twenty-nine percent underwent pharyngeal surgery at the time of first MVTI procedure, and of these, 7.4% (1,096) had pharyngeal surgery in the absence of adenoid or tonsil disease. Adenoid surgery at time of MVTI was associated with reduced odds of subsequent MVTI procedures in children with or without adenoid/tonsil disease. In more recent calendar periods, no differences in the length of hospital stay between MVTI alone and with adenoidectomy was observed, whereas procedures involving tonsils required an additional bed day per procedure and were associated with more episodes of operative and postoperative hemorrhage. CONCLUSION: Having adenoidectomy or adenotonsillectomy surgery at time of first or subsequent MVTI was associated with reduced risk of further MVTI surgery. The low complication rates for adenoidectomy and short hospital stays make adjunctive adenoidectomy a potentially cost-effective first line management option for otitis media with effusion.

Conditionally reprogrammed primary airway epithelial cells maintain morphology, lineage and disease specific functional characteristics.

Current limitations to primary cell expansion led us to test whether airway epithelial cells derived from healthy children and those with asthma and cystic fibrosis (CF), co-cultured with an irradiated fibroblast feeder cell in F-medium containing 10 µM ROCK inhibitor could maintain their lineage during expansion and whether this is influenced by underlying disease status. Here, we show that conditionally reprogrammed airway epithelial cells (CRAECs) can be established from both healthy and diseased phenotypes. CRAECs can be expanded, cryopreserved and maintain phenotypes over at least 5 passages. Population doublings of CRAEC cultures were significantly greater than standard cultures, but maintained their lineage characteristics. CRAECs from all phenotypes were also capable of fully differentiating at air-liquid interface (ALI) and maintained disease specific characteristics including; defective CFTR channel function cultures and the inability to repair wounds. Our findings indicate that CRAECs derived from children maintain lineage, phenotypic and importantly disease-specific functional characteristics over a specified passage range.

Decreasing rates of middle ear surgery in Western Australian children.

OBJECTIVE: To investigate temporal, social, demographic, and health care utilization factors associated with myringotomy with ventilation tube insertion (MVTI) in Western Australian (WA) children. DESIGN: Observational retrospective population-based cohort study using hospital administrative data. SETTING: All WA hospitals. PARTICIPANTS: A total of 53 673 children younger than 15 years who underwent surgery for MVTI in the period 1981-2004. MAIN OUTCOME MEASURES: Age-specific incidence rates and incidence rate ratios. RESULTS: The rate of MVTI in children younger than 15 years peaked in 1997 at 6.7 per 1000 person-years and decreased to 5.6 per 1000 person-years by 2004. Based on 2004 rates, 8.4% of WA children will undergo at least 1 MVTI procedure before reaching age 15 years. The rate of MVTI was 37% lower in Indigenous children, and the procedures were performed at an older age compared with non-Indigenous children. Higher rates of MVTI were associated with areas of higher economic resources, lower education and occupation status, and living in metropolitan areas. CONCLUSIONS: The rate of MVTI in WA is showing evidence of a decline, even among children younger than 5 years. There remains an issue regarding equity of access to care for Indigenous children. Increasing parental economic resources may be associated with higher rates of MVTI independent of educational status.

Adenotonsillectomy for obstructive sleep apnea in obese children: effects on respiratory parameters and clinical outcome.

OBJECTIVE: To assess the efficacy of adenotonsillar surgery on respiratory sleep parameters and avoiding continuous positive airway pressure (CPAP) treatment in morbidly obese children with obstructive sleep apnea syndrome (OSAS). DESIGN: Retrospective. SETTING: Tertiary referral institution. PATIENTS: Children aged 2 to 18 years, with a body mass index (BMI) at or higher than the 95th percentile (adjusted for age and sex), undergoing adenotonsillar surgery for OSAS. INTERVENTIONS: Adenotonsillectomy. MAIN OUTCOME MEASURES: Preoperative and postoperative respiratory disturbance index, oxygen saturation nadir, overall severity of OSAS (mild, moderate, or severe) and candidacy for CPAP treatment were assessed and compared. Variables such as age, severity of disease, adenotonsillar size, and BMI z scores were compared between responders and nonresponders to surgical treatment. RESULTS: A total of 19 patients with full preoperative and postoperative data for evaluation were identified. The median (SD) age was 78 months (53.3 months). The median (SD) BMI z score was 2.84 (0.94). Eighteen patients (95%) had OSAS preoperatively to warrant CPAP treatment. Surgery reduced the overall median (SD) respiratory disturbance index from 20.7 (24.5) to 7.3 (14.9) (P<.001) and improved the median (SD) oxygen saturation nadir from 77.5% (16.3%) to 88.5 (13.1%) (P<.01). A total of 7 patients (37%) were cured by surgery. Ten patients (53%) had postoperative disease of sufficient severity to require CPAP. Surgery obviated the need for further treatment in only 8 (44%) of the 18 patients with preoperative disease warranting CPAP. No differences were identified between responders and nonresponders to surgical treatment. CONCLUSIONS: Adenotonsillar surgery improves sleep respiratory parameters in morbidly obese children with OSAS. Most patients have residual OSAS requiring further treatment.

Congenital cervical teratomas: diagnostic, management and postoperative variability.

OBJECTIVE: To review the diagnosis, management and outcomes of congenital cervical teratomas presenting to a tertiary referral centre. METHODS: Retrospective chart review of three cases presenting within an 18-month period. RESULTS: Of the three patients in this series, one was diagnosed antenatally. The remaining cases were diagnosed at birth. The antenatally diagnosed patient underwent an EXIT procedure whereby the airway was secured by tracheostomy. This patient subsequently died 30 min after separation from the materno-foetal circulation. Neither of the other two cases had any neonatal respiratory distress, despite having large tumours. Both patients had neonatal surgical excision of the teratomas performed. Both patients had postoperative respiratory distress, requiring intervention. Both patients made a full recovery. No recurrence has been reported. CONCLUSION: The antenatal diagnosis of large congenital cervical teratomas allows for planned intervention by experienced personnel. A successful outcome may not be obtained. All patients that undergo surgical excision of these tumours must be closely observed for post-operative respiratory distress, even in the absence of pre-operative symptoms.

Obstructive sleep apnea, morbid obesity, and adenotonsillar surgery: a review of the literature.

Obstructive sleep apnea syndrome is a common occurrence in the obese pediatric population. As this subgroup is rapidly expanding, these children will be increasingly encountered by the otolaryngologist in practice. The literature regarding the etiology, pathogenesis, diagnosis and surgical treatment of obstructive sleep apnea in morbidly obese children is reviewed and pertinent data presented.

Factors associated with developing cholesteatoma: a study of 45,980 children with middle ear disease.

OBJECTIVES/HYPOTHESIS: To identify factors associated with the rate of developing cholesteatoma following ventilation tube insertion (VTI). STUDY DESIGN: A population-based retrospective cohort study. METHODS: Administrative health data from all private and public hospitals in Western Australia for children who had at least one VTI from 1980 to 2004 was used to identify subsequent hospital admissions for cholesteatoma. Main outcome measures were time to cholesteatoma (survival) outcomes, including hazard ratios, log-rank tests, and Kaplan-Meier failure functions. RESULTS: There were 45,980 children who underwent at least one VTI from 1980 to 2004 with 460 subsequently developing cholesteatoma. The cumulative percentage of children who developed cholesteatoma within 15 years after one VTI procedure was 0.9% (95% confidence interval [CI], 0.8-1.0), after two VTIs 2.1% (95% CI, 1.6-2.3), after three VTIs 3.8% (95% CI, 2.9-4.8), and after four or more VTIs 5.2% (95% CI, 4.0-6.7). The rate of developing cholesteatoma increased 10% (95% CI, 6-14) for each additional year in age before first VTI. For children who underwent two or more VTIs, the rate of cholesteatoma increased 21% (95% CI, 12-32) with each additional year between VTIs. Adenoid removal was associated with a 27% (95% CI, 11-40) reduction in the rate of developing cholesteatoma. CONCLUSIONS: Children with persistent or refractory middle ear disease who required multiple VTIs were at increased risk of cholesteatoma. First ventilation tubes inserted at an early age, subsequent ventilation tubes inserted without delay, and adenoid removal were associated with a reduced rate of cholesteatoma development.

Complications of otitis media in Indigenous and non-Indigenous children.

In Australia, three to five children die each year because of otitis media complications, and 15 children will suffer permanent hearing loss each year as a result of otitis media. Extracranial complications occur most commonly, and include mastoiditis, cholesteatoma and otitis media with perforation. Intracranial complications are less common, and include meningitis, brain abscess and lateral sinus thrombosis. In Australia, approximately 60% of extracranial and intracranial complications of otitis media occur in children. The contrasting rates of childhood otitis media among Indigenous and non-Indigenous children have implications for the frequency and types of complications occurring in both groups. Otitis media with effusion and acute otitis media predominate among non-Indigenous children, whereas chronic suppurative otitis media (CSOM) occurs most commonly among Indigenous children. The incidence of mastoiditis in Australia is low by international standards (2/100,000 children), but cholesteatoma rates among Indigenous children in Australia are higher than previously estimated (up to 10% in CSOM). A high rate of chronic tympanic membrane perforation occurs among Indigenous children, estimated to be as high as 80%. Intracranial complications of otitis media are uncommon, but are potentially life-threatening and are more likely to occur among Indigenous than non-Indigenous children. Reduced access to medical care, lower socioeconomic status and remote living conditions mean that levels of early childhood hearing loss among Indigenous children are likely to be underestimated. This has implications for early childhood speech and language development and education.