Changing performance of the Health Visitor Distraction Test when targeted neonatal screening is introduced into a health district

Otolaryngology outreach to Komfo Anokye Teaching Hospital: a medical and educational partnership

Background:

Medical and educational partnerships between high- and low-resourced countries provide opportunities to have a long-term meaningful impact on medical training and healthcare delivery.

Methods:

An otolaryngology partnership between Komfo Anokye Teaching Hospital in Kumasi, Ghana, and the University of Michigan Department of Otolaryngology/Head and Neck Surgery has been undertaken to enhance healthcare delivery at both institutions.

Results:

A temporal bone dissection laboratory, with the equipment to perform dedicated otological surgery, and academic platforms for clinical and medical education and residency training have been established.

Conclusion:

This article describes the details of this partnership in otological surgery and hearing health, with an emphasis on creating in-country surgical simulation, training on newly acquired medical equipment and planning regarding the formulation of objectified metrics to gauge progress going forward.

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.

Health visitor screening versus vigilance: outcomes of programmes for detecting permanent childhood hearing loss in west Berkshire

The Health Visitor Distraction Test (HVDT) screen for hearing was replaced in West Berkshire in 1989 with a vigilance programme incorporating a questionnaire. The detection of permanent congenital deafness (bilateral > 50 dB HL) for all children born since 1984 has been audited to compare the two regimes. Sixty-two cases met the criteria, giving an ascertainment of 1.0 per 1000. Performance was similar under the two systems for severe/profound losses (> 70 dB HL), but there was a longer tail of late-detected moderate losses (50-70 dB HL) under the vigilance regime. The sensitivity of the Health Visitor questionnaire in referring those with permanent hearing loss was very similar to that of the HVDT (39% compared with 42%). Coverage for the questionnaire was approximately 87%, but only 78% for the known cases. Referral rate was lower under the vigilance programme, at approximately 3%. The results suggest that a vigilance programme is likely to perform as well as the HVDT but no better. Despite subsequent modifications to the vigilance programme, the poor pickup of moderate losses probably indicates the limitations of parental and professional observation in detecting partial hearing problems. The evidence adds support to the recent recommendations for universal neonatal screening.

Field sensitivity of targeted neonatal hearing screening using the Nottingham ABR Screener

OBJECTIVE

A population of children having bilateral moderate to profound hearing impairment was investigated to find out the number who passed (false negatives) and who failed (true positives) a screening test based on the auditory brain stem response (ABR).

DESIGN

This study of the ABR is a parallel report to Lutman, Davis, Fortnum, and Wood (1997), where the transient evoked otoacoustic emission was examined on a similar but not identical population of at-risk neonates. Hearing screening was undertaken in at-risk neonates (targeted screening) at seven hospitals in the UK using the Nottingham ABR Screener. During the period from January 1988 to December 1993, a total of 6983 neonates had been tested. Assessment of audiological records from the participating centers ascertained that 201 children born between January 1988 and December 1993 had hearing threshold levels in both ears of 50 dB or more, averaged over the speech frequencies 0.5, 1, 2, and 4 kHz. Of these, 51 had completed the ABR screening test. Examination of the ABR records, which included both machine and visual scoring, indicated whether they had passed or failed the screening test.

RESULTS

Forty-six of the 51 hearing impaired babies failed the neonatal ABR screen either on one or both ears (five false negatives), and 42 failed the test on both ears (nine false negatives). This resulted in field sensitivities of 90% and 82%, respectively. Two cases of suspected progressive hearing loss have been included in the numbers of false negative results. The percentage of babies passing the screen on both ears and subsequently having normal hearing (specificity) is typically 93%.

CONCLUSIONS

Neonatal hearing screening in an at-risk population using a highly automated ABR test is a viable and effective tool for identification of hearing impairment. Although the field sensitivity of the test is high, it is unable to identify all babies with a criterion level of hearing loss. There are a number of possible explanations as to the origin of false negative results: configuration of the pure-tone audiogram, a progressive hearing loss, acquired sensorineural or conductive loss, retrocochlear deafness, or an incorrect interpretation of the screening test. Passing a neonatal screening test, therefore, does not exclude the possibility of subsequent hearing impairment and highlights the need for further surveillance.

Epidemiology of permanent childhood hearing impairment in Trent Region, 1985-1993

This retrospective study of permanent childhood hearing impairment (PCHI) > or = 40 dB HL in children born between 1985 and 1993 and resident in Trent Health Region, achieved an ascertainment of 92.9% of that expected from previous studies and 100% for the subset of children born between 1985 and 1990. The prevalence rate of all permanent hearing impairment > or = 40 dB HL for the birth cohort 1985-90 is 133 (95% confidence interval, (ci) 122-145) per 100,000 live births (1 in 750). Sixteen per cent of PCHI were postnatally acquired, late-onset or progressive impairments. Excluding these, the prevalence rate for congenital impairments is 112 (ci 101-123) per 100,000 (1 in 900). The rate for profound impairments > or = 95 dB HL is 24 (ci 20-30) per 100,000 live births (1 in 4150). Prevalence was increased sixfold for children with a history of neonatal intensive care and 14-fold for children with a family history, compared with children with no risk factors. A more than two-fold increase in prevalence was seen in Asian children. For the congenitally-impaired children born between 1985 and 1990, 29% had a stay in neonatal intensive care > or = 48 hours, 30% had a family history of permanent childhood hearing impairment, and 12% had a cranio-facial abnormality (CFA). Over 59% were potentially detectable by a targeted neonatal screening programme using these three high-risk factors. For 1985-1993, the overall yield of the targeted neonatal screening programmes available in three of the 11 health districts was 15% but increased over time. The overall yield from the Health Visitor distraction test was 30% but lower in districts with neonatal screening programmes. Only 59% of children had a stated aetiology, classified by time of onset into genetic, including syndromes and CFA (41%), pre- or peri-natal (10%), post-natally acquired (6%), and uncertain onset (2%). Just under 40% of the children were said to have another clinical or developmental problem, about half of whom had at least two additional problems. The median age at referral, confirmation of the impairment, prescription of the hearing aid and fitting of the hearing aid were, respectively, 10.4 months, 18.1 months, 24.4 months and 26.3 months. A more severe impairment was associated with earlier age. Small improvements in the median age of hearing aid prescription and fitting were seen over time. Twenty-five per cent of children were referred for genetic counselling, the proportion increasing systematically with the severity of the impairment. Based on evidence of the yield from hearing screens we suggest a wider implementation of neonatal screening and further consideration of the role of the health visitor distraction test in the identification of children with PCHI. To facilitate further assessment of services for hearing-impaired children we suggest implementation of a co-ordinated shared list of children with permanent hearing impairment on a region-wide basis to provide adequate numbers for comparison over time, and the routine collection of a minimum set of data for each child.