The age of identification of childhood deafness--improvements since the 1970s

Performance of neonatal and infant hearing screens: sensitivity and specificity

The terms 'sensitivity' and 'specificity' are defined and some of the factors that determine their values are discussed in the context of screening for permanent childhood hearing loss. There is a need to distinguish between the values observed in 'simple experiments' and those that may be obtained under more realistic 'field' conditions. It is not feasible to give a meta-analytic overview of published data because of the variety of methods and objectives used in those studies published in the literature. However, a qualitative synthesis of the data is possible. This suggests that most proposed neonatal hearing screening tests, when implemented in accordance with a programme of quality assurance, can be reasonably accurate at a modest cost. However, the optimal combination of tests and test parameters for given populations has not yet been fully researched. The infant distraction test screen has a lower sensitivity than neonatal hearing screening tests, particularly for moderate impairments, accompanied by a fairly low specificity.

Neonatal hearing screening using the auditory brainstem response

A targeted screen of babies at risk of having a sensorineural hearing loss (SNHL) using the auditory brainstem response has been in place since 1987 in Bradford and Airedale. The aims of this paper were to ascertain what proportion of a 4-year cohort of children with SNHL should have been identified by the programme; was identified by the programme; and the reasons for failing when children were missed. The cohort of 49 children had moderate to profound SNHL (> 50 dB) and were born between 1 April 1991 and 31 March 1995. Although 92% had at risk factors (higher than in other series), 80% was the maximum that could have been prospectively detected by the programme and only 37% were actually diagnosed as a result of the screening programme. Apart from a generalised under-recruitment, children with risk factors arising because of in utero, perinatal and postnatal events (as opposed to family history, craniofacial abnormalities and syndromes) tended to be missed (P < 0.01). The overall yield of the screening programme was 0.5/1000/year. While the yield of a universal neonatal screening programme based on otoacoustic emissions should be double this, a targeted infant distraction test later in infancy will be an essential backup. Improved liaison with paediatricians in particular as well as simplification of the referral criteria should improve targeting children at risk.

Outcomes of neonatal screening for hearing loss by otoacoustic emission

AIM

To assess universal neonatal screening for bilateral hearing impairments averaging 40 dBHL or worse in the better ear, using transient evoked otoacoustic emission screening (TEOAE) testing.

METHODS

A three year cohort (14,353 infants born from January 1992 to 1995) was screened and subsequently followed up by hearing surveillance methods, including a distraction test screen from 7 months of age. The entire cohort was used to evaluate the outcome of the screen. A subcohort of 8172 district residents was used to evaluate the continuing worth of the distraction test programme.

RESULTS

Nineteen infants (1.3/1000) with a targeted hearing impairment failed the neonatal TEOAE test. Six profoundly deaf infants identified by the TEOAE screen, were fitted with hearing aids at a median age of 16 weeks. One remained without an aid. Of 12 infants with a moderate impairment, only seven accepted hearing aid fitting and the median age of being fitted with an aid increased to 42 weeks. By the time of the analysis 22 children with a targeted hearing impairment (1.5/1000) had been identified from the cohort. Of the three missed neonatally, one was cared for elsewhere, another had a progressive loss, and the third had central deafness. Twenty children were ascertained with a congenital peripheral deafness. Of these, eight (40%) had risk factors identifiable neonatally. Only the child with central deafness was missed by TEOAE screening and subsequently identified by behavioural tests in infancy. The TEOAE screen outperformed the distraction test in terms of processes and yield and was 25% less expensive.

CONCLUSIONS

The analysis confirmed the worth within the district of the TEOAE hearing screen. It will thus be continued as a universal neonatal screen with the distraction test being retained as a selective screen in the latter half of infancy.

Prevalence, aetiology, and care of severe and profound hearing loss

Severe and profound hearing loss (> 70 dB) were analysed in a retrospective study of 226 children, born between 1976 and 1985, and recruited from three French administrative departments. The prevalence was 0.54 per 1000 children under 9 years old, with no decrease over the study period. A hereditary origin was identified in 20.8% of cases and an infectious origin in 11.5%. Perinatal risk factors were present in 11.5%, while the aetiology was undetermined in more than half the cases. In 85.8% of the children there was no other severe impairment. Marked learning difficulties were observed: 36% of the children were two years behind their age group and 28% were more than two years behind. The age of initial care decreased over the study period but is still too advanced. Systematic neonatal screening would enable earlier care, which should limit the social and educational impact of hearing loss.

Auditory brainstem response screening for hearing loss in high risk neonates

The present paper reports the findings of a 7 year study evaluating the use of the auditory brainstem response (ABR) as the basis of a hearing screening procedure in a group of newborns at increased risk of hearing impairment. A Special Care Baby Unit (SCBU) population of 417 infants with diverse clinical backgrounds and treatment histories was tested for hearing impairment at birth using ABR audiometry. Some 332 passed the original screen at 30 dBnHL test level in both ears. Of the failure group, 18 did not survive and 32 had some degree of hearing impairment confirmed, nine of which were sensorineural in origin. An increased incidence of persistent middle ear disease was also noted in the failure group. A detailed operational analysis demonstrates that provided appropriate pass/fail criteria are adopted, the ABR technique offers excellent sensitivity and specificity for the detection of significant hearing loss in the test population. Furthermore, the study establishes that implementation of an ABR-based screening programme could reduce the average age at detection of permanent hearing loss by 7 months. A cost assessment shows that the introduction of such a targetted screening procedure could be done at a reasonable outlay.

Neonatal otoacoustic emission screening and the identification of deafness

Using transient evoked otoacoustic emissions (TEOAEs), a two stage screen with the testing of failures by auditory brainstem response (ABR), has been implemented in Whipps Cross Hospital in East London. From January 1992 to 1995, 11,606 infants received an initial TEOAE test. Once initial difficulties were resolved, coverage of district residents remained stable at 91.5%. Long term follow up of the cohort is being undertaken. Of those receiving an initial test, 13% failed in both ears. Only 1.75% of the cohort failed both stages of the TEOAE screen bilaterally. These infants were tested by ABR. The yield of infants with a bilateral permanent hearing loss of moderate or worse degree was 2/1000. The overall cost of implementing the programme was not prohibitive and the cost per hearing impaired child detected was little more than the widely accepted notional cost of identifying such children through targeted at risk screens. The screen was clearly sensitive. The priority for such universal TEOAE programmes, however, is to increase specificity without losing this sensitivity.

Hearing loss and other ear problems among schoolboys in Abha, Saudi Arabia

The aim of this work was to determine the prevalence of hearing loss (HL) and its association with different ear problems among schoolboys in Abha City, Asir Region, Saudi Arabia. A representative sample of 974 schoolboys ages six to 12 years were subjected to both audiometric and otoscopic examinations. Audiometric examination identified 43 children with HL (40 conductive and three sensorineural), making a prevalence of 4.4% (1.7% mild, 2% moderate and 0.7% severe HL). Otoscopic examination revealed ear problems among 26.9% of schoolboys with the following prevalences: wax (21.3%), acute otitis media (1.9%), chronic otitis media (1.0%), foreign body (0.7%), otitis externa (0.7%), and congenital anomaly of the auricle (0.4%). Impacted wax accounted for reversible HL among a quarter (25.6%) of the hearing impaired children, whereas chronic otitis media accounted for 11.6%; acute otitis media 9.3%; otitis media with effusion, foreign body and congenital anomaly of the auricle each accounted for 2.3%. A significantly higher frequency of HL was detected among children with otitis media than among children without ear conditions (29.4% vs. 2.8%, P<0.01). The prevalence of HL among Abha schoolboys was comparable to that in developed countries, but was lower than that in developing countries. Such prevalence was mostly caused by impacted wax and otitis media. Thus, attention should be given to regular screening for early detection and removal of the impacted wax for correcting the high prevalence of reversible HL due to such conditions. Children of low social class should be regarded as a high risk group for whom regular hearing screening is recommended.

Neonatal at risk screening and the identification of deafness

From a cohort of 10,686 live births, 322 (3%) were identified as being at risk of a hearing impairment defined as moderate, or worse. These neonates were screened by measurement of auditory brainstem responses. The neonatal at risk screening programme was effective in terms of both yield and cost. The mean age at which hearing aids were fitted was 6 months in the children identified by the neonatal screen. Such a programme is both practicable and useful in a district general hospital. The yield from the neonatal programme was, however, only 43% of the total number of deaf children eventually identified from the cohort. The need to identify more deaf children by a sensitive infant distraction test screening programme remains.