Identification of permanent hearing loss in children: are the targets for outcome measures attainable?

Study of the hearing loss in children and adolescents, comparing the periods of 1990-1994 and 1994-2000

INTRODUCTION

In 1994, a study was performed with 200 children and adolescents suffering from hearing loss. It concluded that the diagnostic confirmation of hearing loss within 2 years of age occurred in just 13% of the cases, although 56% were suspected in that phase. The loss of time of over 2 years between suspicion and confirmation of hearing loss occurred in 42% of the cases.

OBJECTIVES

The comparison of the main hearing loss etiologies-genetic cause, consanguinity, congenital rubella, meningitis, perinatal events and unknown causes-in children and adolescents in the periods of 1990-1994 and 1994-2000; comparison of incidence, in males and females, for each etiology and among the others; comparison of age at the first consultation, for each and among them; and the investigation as to whether the time between suspicion and diagnosis of hearing loss was different for each etiology and among the others.

METHODS

During the period of 1990-2000, of the 519 children and adolescents with hearing loss, 442 individuals were selected, in the two moments of the study: 1990-1994 and 1994-2000. The variables used were: sex, age at first consultation, suspected etiology and time between suspicion and confirmation of hearing loss.

RESULTS

Congenital rubella, genetic and perinatal causes, meningitis, consanguinity and unknown causes were responsible for over 80% of all etiologies, in both periods. There were no differences between the sexes in the periods studied. There was no relation among age, sex and etiology. Among the etiologies studied, there were no differences in the lengths of times between suspicion and confirmation of hearing loss, in each period separately. The comparative study showed that congenital rubella, genetic and unknown causes took longer times between suspicion and confirmation of hearing loss, for the period of 1990-1994, as compared with 1994-2000.

CONCLUSIONS

Congenital rubella remains as an important etiology, as well post-meningitis deafness. Age at first consultation did not show relationship to the hearing loss etiology nor to sex. Independently of whether the etiology being pre-natal, perinatal or post-natal, congenital or acquired, the length of time between suspicion and confirmation of hearing loss did not differ between the periods studied, separately.

Comparing the clinical effectiveness of different new-born hearing screening strategies. A decision analysis

Background

Children with congenital hearing impairment benefit from early detection and treatment. At present, no model exists which explicitly quantifies the effectiveness of universal newborn hearing screening (UNHS) versus other programme alternatives in terms of early diagnosis. It has yet to be considered whether early diagnosis (within the first few months) of hearing impairment is of importance with regard to the further development of the child compared with effects resulting from a later diagnosis. The objective was to systematically compare two screening strategies for the early detection of new-born hearing disorders, UNHS and risk factor screening, with no systematic screening regarding their influence on early diagnosis.

Methods

Design: Clinical effectiveness analysis using a Markov Model.

Data Sources: Systematic literature review, empirical data survey, and expert opinion. Target Population: All newborn babies.

Time scale: 6, 12 and 120 months.

Perspective: Health care system.

Compared Strategies: UNHS, Risk factor screening (RS), no systematic screening (NS). Outcome Measures: Quality weighted detected child months (QCM).

Results

UNHS detected 644 QCM up until the age of 6 months (72,2%). RS detected 393 child months (44,1%) and no systematic screening 152 child months (17,0%). UNHS detected 74,3% and 86,7% weighted child months at 12 and 120 months, RS 48,4% and 73,3%, NS 23,7% and 60,6%. At the age of 6 months UNHS identified approximately 75% of all children born with hearing impairment, RS 50% and NS 25%. At the time of screening UNHS marked 10% of screened healthy children for further testing (false positives), RS 2%. UNHS demonstrated higher effectiveness even under a wide range of relevant parameters. The model was insensitive to test parameters within the assumed range but results varied along the prevalence of hearing impairment.

Conclusion

We have shown that UNHS is able to detect hearing impairment at an earlier age and more accurately than selective RS. Further research should be carried out to establish the effects of hearing loss on the quality of life of an individual, its influence on school performance and career achievement and the differences made by early fitting of a hearing aid on these factors.

Neonatal screening for hearing impairment

Over the last 25 years, technological developments have facilitated the implementation of neonatal screens for hearing impairment. Restricting tests to 10% of the cohort with risk factors enables detection of around 40% of congenital impairments. Critical review has therefore recommended universal screening targeting for identification all neonates with moderate or worse impairment. Both oto-acoustic emission and auditory brainstem response (ABR) recording make this possible. The emission test is very sensitive to mild impairments. Specificity critically depends upon the age of maternity testing, but a false positive rate of 8% at discharge is typical. This is reduced to <1% by implementing a second outpatient test, or an ABR before discharge. Both tests are required to identify auditory neuropathies. Widespread implementation will follow pilot trials that are currently being undertaken. The accurate assessment of screen positives, and appropriate habilitation for those identified, is also required. These needs are complex, and require further study if universal screening is to become routine.

A Two-stage bipodal screening model for universal neonatal hearing screening

OBJECTIVE

A model is proposed for universal neonatal hearing screening.

METHODS

The screening model is two-staged because it consists of a first test and, in case of failure (1.4% of the subjects), of a retest 3 weeks later. It is bipodal because it involves both the hospital audiologic department and a central Well Baby Organization. The idea is to have a maximal number of newborns tested at the maternity by trained audiologists and to have the Well Baby Organization trace and chase the missing subjects. The model has been evaluated during 1 calendar year (1999) in a maternity with 2,012 newborns.

RESULT

The result is a coverage of 99.3%. Most newborns (97.3%) were tested at the maternity ward with a total time investment of less than 15 minutes per child. The actual test time is 2 minutes, 12 seconds (median value). The Well Baby Organization keeps track of all the results and has to test no more than 2% of the newborns. Sensitivity and specificity were not the primary outcomes of this evaluation, but they were similar to those of a previous study evaluating the screen procedure on a larger scale, giving a sensitivity of approximately 100% and a false alarm rate of 1/1,000.

CONCLUSION

These figures demonstrate that universal neonatal hearing screening is feasible within the existing health care structure, with unprecedented coverage, sensitivity, and specificity.

How do we identify hearing impairment in early childhood?

This review discusses the need for universal neonatal hearing screening. Historical background is given concerning conventional childhood hearing screening programmes in western countries. Direct studies on the effects of very early habilitation programmes on speech and language development are cited. Measurement of otoacoustic emissions (OAE) as a tool for neonatal hearing screening is presented. The state of neonatal hearing screening programmes in the US and in Europe, particularly in Sweden, is discussed.