Permanent hearing loss is one of the commonest
congenital disorders with the incidence being much more than the
conditions newborns are routinely screened for. Most neonatal hearing
loss is sensorineural and a known genetic cause can be found in only
50%. Universal Neonatal Hearing Screening (UNHS) is restricted to
developed countries due to cost of delivery and manpower required in
screening. It has been conclusively shown to significantly lower the age
of diagnosis of children with hearing loss [1]. Targeted screening of
high risk infants would miss 50% of babies that would have been
identified by UNHS [2]. In the absence of a screening program, hearing
loss is typically identified with language delay around 24 months of age
in contrast to three months or younger in the screened population with
intervention by six months. Screening has reduced the age, at which
infants receive hearing aids, from 13-16 months to 5-7 months in
developed countries [3].
Auditory stimuli during the first 6 months of life
are critical for the development of speech and language skills. Several
studies have shown that infants who receive intervention before the age
of 6 months have better school outcomes, and improved language and
communication skills by ages 2 to 5 years [4]. Without early
intervention, children with hearing loss will show irreversible deficit
in communication, psychosocial skills and literacy. They are more likely
to have academic underachievement, problems with employment and
psychological distress.
Screening can be performed by otoacoustic emissions
(OAE) or automated auditory brainstem response (AABR) testing. OAE is
technically easier and faster to perform. It is cheaper but has higher
false positive rates of about 15%. It also requires a quite or a
soundproof room. In comparison, AABR has less false positives and can
also detect patients with auditory neuropathy unlike OAE. It is best to
screen after 24 hours as pass rate increase from 70% to 82% if done
after 24 hours [5]. This may be attributed to obstruction of ear canal
with vernix, debris and amniotic fluid in the early period.
There are limitations with hearing screening. UNHS
will not identify progressive and late onset hearing loss as well as
less severe hearing loss (<40dB). The false positive rate is around 2%
that is similar to thyroid screening. This can cause anxiety in parents
[6]. An effective program needs a large amount of organization and
should have an integrated diagnosis, intervention and follow-up plan. In
developed world where the state pays for health care, the benefits of
UNHS outweigh the costs. However, the cost effectiveness has not been
established in developing countries.
The study in this issue by Augustine, et al.
[7] used BERAphone (AABR) for screening the infants. They found that the
BERAphones were easy to use and worked well even in high ambient noise.
First screening was achieved in 97.7 % infants that is above 95%
recommended by the Joint Committee on Infant Hearing (JCIH) [2]
suggesting that screening is feasible and effective. Confirmatory
testing was done between 1 to 3 months but there was a big drop in the
number who attended, with just under one-third undergoing the
confirmatory test. This problem has been sighted in other programs,
including those in the developed countries. Studies have shown the main
reasons for a drop-out to be: lack of communication with parents, lack
of booking of appointments, problems in transportation and lack of
understanding of parents about importance of early diagnosis and
intervention [8].
The authors have shown that UNHS using BERAphone is
feasible. However, the large loss to follow-up is a big hurdle for any
screening program to achieve its objective. This is compounded by the
fact that babies with previous risk factors are more likely to attend
follow-up, making universal hearing screen not much more effective
compared to targeted screening. To be really effective, screening needs
to be coupled with an early intervention program without which there
would be no benefit in early diagnosis. In developing countries like
India with the high attrition rate in follow-up, the cost effectiveness
of UNHS as well as its comparison with targeted screening needs to be
evaluated.
Funding: None; Competing interest: None
stated.
References
1. Nelson HD, Bougatsos C, Nygren P. Universal
newborn Hearing screening: systematic review to update the 2001 US
Preventive Services Task Force Recommendation. Pediatrics.
2008;122:e266-76.
2. American Academy of Pediatrics, Joint Committee on
Infant Hearing Year 2007 position statement: Principles and guidelines
for early hearing detection and intervention programs. Pediatrics.
2007;120:898-921.
3. Canale A, Favero E, Lacilla M, Recchia E,
Schindler A, Roggero N, et al. Age at diagnosis of deaf babies: A
retrospective analysis highlighting the advantage of newborn hearing
screening. Int J Pediatr Otorhino-laryngol. 2006:70:1283-9.
4. Pimperton H, Kennedy CR. The impact of early
identification of permanent childhood hearing impairment on speech and
language outcome. Arch Dis Child. 2012;97:648-53.
5. Vohr BR, White KR, Maxon AB, Johnson MJ. Factors
affecting the interpretation of transient evoked otoacoustic emission
results in neonatal hearing screening. Semin Hearing. 1993;14:57-72.
6. Patel H, Feldman M. Universal newborn screening.
Paediatr Child Health. 2001;16:301-5.
7. Augustine AM, Jana AK, Kuruvilla KA, Danda S,
Lepcha A, Ebenezer J, et al. Neonatal hearing screening –
Experience from a tertiary care hospital in Southern India. Indian
Pediatr. 2014;51:179-83.
8. Mukhari SZ, Tan KY, Abdullah A. A pilot project on
hospital-based universal newborn hearing screening: Lessons learned. Int
J Pediatr Otorhinolaryngol. 2006;70:843-51.