Place of birth and characteristics of infants with congenital and early-onset hearing loss in a developing country

Outcomes of Universal Newborn Screening Programs: Systematic Review

BACKGROUND

This systematic review examined the outcomes (age of identification and intervention, developmental outcomes, cost-effectiveness, and adverse effects on parents) of universal newborn hearing screening (UNHS) for children with permanent congenital hearing loss (PCHL).

MATERIALS AND METHODS

Multiple electronic databases were interrogated in March and April 2020 with further reports identified from article citations and unpublished literature. UNHS reports in English with comparisons of outcomes of infants who were not screened, and infants identified through other hearing screening programs.

RESULTS

30 eligible reports from 14 populations with 7,325,138 infants screened through UNHS from 1616 non-duplicate references were included. UNHS results in a lower age of identification, amplification, and the initiation of early intervention services and better language/literacy development. Better speech perception/production were shown in younger, but not in older, children with early identification after UNHS. No significant findings were found for behavior problems and quality of life. UNHS was found to be cost-effective in terms of savings to society. In addition, no significant parental harm was noted as a result of UNHS.

CONCLUSIONS

In highly developed countries, significantly better outcomes were found for children identified early through UNHS programs. Early language development predicts later literacy and language development.

Profile of childhood hearing loss in the Western Cape, South Africa

OBJECTIVES

To describe the nature, associated risk factors and age of diagnosis for childhood hearing loss in a South African cohort from the Western Cape Province.

METHODS

A retrospective review of clinical data from children under six years of age with confirmed hearing loss at Red Cross War Memorial Children's Hospital (RCWMCH) was conducted between 1 January 2019 and 31 July 2019. Data collected included demographic information, type and degree of hearing loss, documented risk factors associated with hearing loss, and age of suspicion and diagnosis of hearing loss.

RESULTS

The study sample included 240 children with hearing loss, with a mean age of 42 months (21.8 SD; range 2-72). More than two thirds (68.3%) of the children presented with bilateral hearing loss. The majority presented with conductive hearing loss (64.6%), followed by sensorineural (28.7%) and mixed hearing loss (3.3%) or auditory neuropathy spectrum disorder (3.3%). More than half (51.8%) of the bilateral sensorineural hearing losses were of a profound degree. The most prominent risk factor for conductive hearing loss was otitis media, for sensorineural hearing loss it was a family history of childhood hearing loss, and for auditory neuropathy spectrum disorder it was hyperbilirubinaemia. Approximately one third of patients (27.1%) with sensorineural hearing loss did not have any associated risk factors. The mean age of diagnosis of permanent congenital or early-onset hearing loss was 31.4 months (22.8 SD; range 2-72), with a mean delay of nine months (13.2 SD; range 0-60) between age of suspicion and diagnosis of hearing loss (n = 93).

CONCLUSIONS

The large proportion of preventable hearing losses in this sample highlights the importance of maximising primary health care efforts to treat preventable causes timeously. Age of diagnosis of permanent congenital or early-onset hearing loss was severely delayed undermining prospects of positive outcomes through early intervention. Infant hearing screening services in the public health sector of South Africa should be prioritised alongside primary health care efforts to reduce preventable risks for hearing loss.

Evaluation of universal newborn hearing screening in South African primary care

BACKGROUND

Universal Newborn Hearing Screening (UNHC) is the gold standard toward early hearing detection and intervention, hence the importance of its deliberation within the South African context.

AIM

To determine the feasibility of screening in low-risk neonates, using Otoacoustic Emissions (OAEs), within the Midwife Obstetric Unit (MOU) three-day assessment clinic at a Community Health Centre (CHC), at various test times following birth.

METHOD

Within a quantitative, prospective design, 272 neonates were included. Case history interviews, otoscopic examinations and Distortion Product OAEs (DPOAEs) screening were conducted at two sessions (within six hours and approximately three days after birth). Data were analysed via descriptive statistics.

RESULTS

Based on current staffing profile and practice, efficient and comprehensive screening is not successful within hours of birth, but is more so at the MOU three-day assessment clinic. Significantly higher numbers of infants were screened at session 2, with significantly less false-positive results. At session 1, only 38.1% of the neonates were screened, as opposed to more than 100% at session 2. Session 1 yielded an 82.1% rate of false positive findings, a rate that not only has important implications for the emotional well-being of the parents; but also for resource-stricken environments where expenditure has to be accounted for carefully.

CONCLUSION

Current findings highlight the importance of studying methodologies to ensure effective reach for hearing screening within the South African context. These findings argue for UNHS initiatives to include the MOU three-day assessment to ensure that a higher number of neonates are reached and confounding variables such as vernix have been eliminated.

Sequencing of GJB2 in Cameroonians and Black South Africans and comparison to 1000 Genomes Project Data Support Need to Revise Strategy for Discovery of Nonsyndromic Deafness Genes in Africans

Mutations in the GJB2 gene, encoding connexin 26, could account for 50% of congenital, nonsyndromic, recessive deafness cases in some Caucasian/Asian populations. There is a scarcity of published data in sub-Saharan Africans. We Sanger sequenced the coding region of the GJB2 gene in 205 Cameroonian and Xhosa South Africans with congenital, nonsyndromic deafness; and performed bioinformatic analysis of variations in the GJB2 gene, incorporating data from the 1000 Genomes Project. Amongst Cameroonian patients, 26.1% were familial. The majority of patients (70%) suffered from sensorineural hearing loss. Ten GJB2 genetic variants were detected by sequencing. A previously reported pathogenic mutation, g.3741_3743delTTC (p.F142del), and a putative pathogenic mutation, g.3816G>A (p.V167M), were identified in single heterozygous samples. Amongst eight the remaining variants, two novel variants, g.3318-41G>A and g.3332G>A, were reported. There were no statistically significant differences in allele frequencies between cases and controls. Principal Components Analyses differentiated between Africans, Asians, and Europeans, but only explained 40% of the variation. The present study is the first to compare African GJB2 sequences with the data from the 1000 Genomes Project and have revealed the low variation between population groups. This finding has emphasized the hypothesis that the prevalence of mutations in GJB2 in nonsyndromic deafness amongst European and Asian populations is due to founder effects arising after these individuals migrated out of Africa, and not to a putative "protective" variant in the genomic structure of GJB2 in Africans. Our results confirm that mutations in GJB2 are not associated with nonsyndromic deafness in Africans.

In search of genetic markers for nonsyndromic deafness in Africa: a study in Cameroonians and Black South Africans with the GJB6 and GJA1 candidate genes

Deafness is the most common sensory disability in the world and has a variety of causes. Globally, mutations in GJB2 have been shown to play a major role in nonsyndromic deafness, but this has not been seen in Africans. Two other connexin genes, GJB6 and GJA1, have been implicated in hearing loss but have seldom been investigated in African populations. We set out to investigate the role of genetic variation in GJB6 and GJA1 in a group of Cameroonian and South African Blacks with nonsyndromic recessive hearing loss. A subset of 100 patients, affected with nonsyndromic hearing loss, from a cohort that was previously shown not to have GJB2 mutation, was analyzed by Sanger sequencing of the entire coding regions of GJB6 and GJA1. In addition, the large-scale GJB6-D3S1830 deletion was also investigated. No pathogenic mutation was detected in either GJB6 or GJA1, nor was the GJB6-D3S1830 deletion detected. There were no statistically significant differences in sequence variants between patients and controls. Mutations in GJB6 and GJA1 are not a major cause of nonsyndromic deafness in this group of Africans from Cameroon and South Africa. Currently, there is no sufficient evidence to support their testing in a clinical setting for individuals of African ancestry.

Childhood hearing loss and risk profile in a South African population

OBJECTIVE

To describe the nature of hearing loss and associated risk profile in a South African population of infants and children diagnosed at a pediatric referral clinic.

METHODS

A retrospective review of patient files for a pediatric auditory evoked potential clinic in Pretoria was conducted (January 2007-December 2011). Collected data included demographical information, risk factors from case history questionnaire, diagnosis (type and degree of hearing loss), documented age of caregiver suspicion and age of first diagnosis.

RESULTS

Hearing loss was present in 73% (73/100) of cases evaluated. Permanent hearing losses (SNHL, ANSD and mixed) constituted 76% of losses. Unilateral hearing losses constituted 8% of SNHL and 20% of conductive hearing loss. ANSD was diagnosed in 21.4% and SNHL in 78.6% of permanent non-conductive hearing loss cases. The most prevalent SNHL risk was family history of hearing loss and for ANSD it was admittance to the NICU for more than 5 days. The majority of the sample was diagnosed with a permanent bilateral SNHL and ANSD after 36 months of age (47%) despite 40% already suspected of having a hearing loss before 12 months of age.

CONCLUSIONS

A high prevalence of ANSD was found with preventable risk factors often indicated. Age of diagnosis was significantly delayed, evidencing the lack of early hearing detection services in South Africa. The majority of children were diagnosed at ages precluding optimal benefits from early detection and subsequent intervention.

Is discordance in TEOAE and AABR outcomes predictable in newborns?

OBJECTIVE

To determine the perinatal predictors of discordant screening outcomes based on a two-stage screening protocol with transient-evoked otoacoustic emissions (TEOAE) and automated auditory brainstem response (AABR).

METHODS

A cross-sectional study of infants tested with TEOAE and AABR under a hospital-based universal newborn hearing screening program in Lagos, Nigeria. Maternal and infant factors associated with discordant TEOAE and AABR outcomes were determined with multivariable logistic regression analyses adjusting for potential confounding factors.

RESULTS

Of the 4718 infants enrolled under the program 1745 (36.9%) completed both TEOAE and AABR. Of this group, 1060 (60.7%) passed both TEOAE and AABR ("true-negatives"); 92 (5.3%) failed both TEOAE and AABR ("true-positive"); 571 (32.7%) failed TEOAE but passed AABR ("false-positives") while 22 (1.3%) passed TEOAE but failed AABR ("false-negatives"). Infants with false-positives were likely to be admitted into well-baby nursery (p=0.001), belong to mothers who attended antenatal care (p=0.010) or who delivered vaginally (p<0.001) compared to infants with true-negatives while infants with true-positives were also more likely to be delivered vaginally (p=0.002) or admitted into well-baby nursery (p=0.035) compared to infants with false-negatives. Infants with true-positives were significantly more likely to be delivered vaginally (p<0.001) and have severe hyperbilirubinemia (p=0.045) compared with infants with true-negatives. No association was observed between false-negatives and true-negatives. Antenatal care status, mode of delivery and nursery type were useful predictors of discordant outcomes among all infants undergoing screening (c-statistic=0.73).

CONCLUSIONS

Given the available screening technologies, discordant TEOAE and AABR may be inevitable for some categories of hearing loss among apparently healthy newborns whose mothers received prenatal care. The potential limitations of perinatal morbidities as basis of targeted screening for such cases therefore merit further consideration.

Non-uptake of facility-based maternity services in an inner-city community in Lagos, Nigeria: an observational study

Scaling-up of skilled attendants and facility-based services is necessary for improving maternal and child care in developing countries but their effectiveness is crucially influenced by the uptake of such services. This study set out to establish the pattern and uptake of maternity services and associated factors against the backdrop of rapid urbanization in Nigeria. A cross-sectional study of socio-demographic and obstetric characteristics of mothers attending the Bacille Calmette-Guérin (BCG) immunization clinics in inner-city Lagos was conducted from July 2005 to December 2007, and their association with non-hospital delivery and use of unskilled attendants was determined by multiple logistic regression analyses. Of the 6465 participants, over half (51.4%) delivered outside hospital facilities and 81.8% of this group had no skilled attendants at delivery. Non-hospital delivery or the presence of unskilled attendants at delivery was associated with teenage mothers, Muslim religion, low or middle social class and use of herbal drugs in pregnancy. Additionally, non-hospital delivery was associated with ethnicity (Yoruba tribe), lack of tertiary education or full-time employment, accommodation with shared sanitation facilities and multiparity. The results suggest that availability of and access/proximity to hospital facilities or skilled attendants is no guarantee of uptake of maternity services. Efforts aimed at improving maternal and child health in developing countries should take cognisance of the socio-demographic and cultural underpinnings of maternal health-seeking behaviour of urban mothers beyond the provision of facility-based services or strengthening of the existing health care systems.