| Abstract|| |
Background: Two thirds of the burden of hearing loss is predominantly in low- and middle-income countries. The World Health Organization estimated about 642 million (10.6%) of the world's population has any level of hearing impairment in 2005. It becomes, therefore, imperative to gather data for the purpose of planning prevention strategies for hearing impairment and for monitoring and evaluation of these programs at primary and national levels. Aim: The aim of this study was to determine the prevalence of hearing impairment and report our findings on hearing screening in a rural setting. Materials and Methods: A total of 37 persons with hearing impairment were identified out of 650 seen with ages ranging from 3 to 60 years in a rural setting. They all had full clinical examination, tuning fork, and voice tests to assess hearing levels and otoscopy. Results: An overall hearing loss prevalence of 5.7% was observed, with commonest causes of hearing loss identified as febrile illness 48.6%, ear infections 32.4%, congenital and meningitis 8.1% each, and measles 2.7%. Conclusion: Prevalence studies and hearing screening programs are necessary to help formulate policies geared toward primary ear and hearing care. This will help reduce the burden of hearing loss as well as help to provide cheap and affordable hearing aids to the needy.
Keywords: Hearing impairment, otoscopy, prevalence, screening, tuning fork
|How to cite this article:|
Ahmed AO, Tsiga-Ahmed FI, Hasheem MG, Ajiya A. Hearing screening techniques for referral purposes: Our experience from a rural setting. Ann Trop Med Public Health 2013;6:173-8
|How to cite this URL:|
Ahmed AO, Tsiga-Ahmed FI, Hasheem MG, Ajiya A. Hearing screening techniques for referral purposes: Our experience from a rural setting. Ann Trop Med Public Health [serial online] 2013 [cited 2020 Jul 14];6:173-8. Available from: http://www.atmph.org/text.asp?2013/6/2/173/116500
| Introduction|| |
In most developing countries, routine screening programs for hearing impairment does not exist and there is perpetual lack of funds to procure much needed equipment for screening and training of skilled manpower. The World Health Organization (WHO) estimated the global burden of "disabling hearing impairment" in 1985 at 42 million, 1995 at 120 million after just 10 years. In 2005 it rose to 278 million, approximately 4.6% of the world's population with moderate to severe hearing impairment and about 642 million (10.6%) have any level of hearing impairment  of which 28% are children. Two thirds of the burden of hearing loss is predominantly in low- and middle-income countries. Disabling hearing impairment in adults is defined as,''a permanent unaided hearing threshold level for the better ear of 41dB or greater measured at 0.5, 1, 2, and 4 kHz" while in "children under the age of 15 years is taken as permanent unaided hearing threshold levels for the better ear of 31dB or greater" at same frequencies as for the adult (WHO, 1997). A new classification has been proposed by the expert group working for the new initiative on the global burden of disease (Global burden, 2008) but is yet to be accepted.
The prevalence of disabling hearing loss increases markedly with age; especially adult-onset this is mainly due to age-related hair cell changes. In a systematic review of prevalence of hearing impairment in sub-Saharan Africa, , it was estimated that the prevalence amongst adults was 15.7% and children 1.9% with men having a higher prevalence compared with women. Against this background, it becomes imperative to gather data for the purpose of planning prevention strategies and for monitoring and evaluation of this programs at primary and national levels. For a proper survey to be conducted and valid for these purposes, certain criteria have been laid down by the WHO program for the prevention of blindness and deafness (WHO/PBD).  Data collected in this way can then be used to carry out economic analysis studies in developing countries with respect to cost of the burden of hearing impairment and the cost-effectiveness of different intervention strategies against it. And by implication will justify and encourage allocation of increased resources by policy makers and relevant ministries in developing countries to this recalcitrant problem.
This may not, however, be that straight forward in some developing countries where health resources are so small that the detection/screening for hearing impairments takes very low priority. Also coupled with the fact that skilled manpower for the management of hearing impairment is scarce, especially in northern Nigeria. In particular, Kano state with a population of over 10 million (2006 census) boasts of one audiometrician, five trained ear, nose and throat (ENT) surgeons to serve three other neighbouring Jigawa, Katsina, and Bauchi states as well.
Furthermore, hearing impairment as a sensory disability is not as recognized as blindness, as evidenced by the amount of blindness programs. Needless to say, many community health extension workers/community health officers are trained for blindness campaigns with little or no exposure/training in primary ear and hearing care. The utilization of these set of health workers can be modelled like the key informant method program in Bangladesh to detect/refer hearing impaired adults and children within communities thereby helping to reduce the untoward effect of hearing loss in these societies.  This approach is still in use in Bangladesh with good results. Similarly, training the community healthcare worker in our environment for the sole purpose of ear and hearing care and the political will to do so is lacking and as such sourcing for funds for deafness prevention programs is equally a herculean task.
Against this background, an attempt was then made during a recent community outreach health program by the Nigerian Medical Association (NMA) Kano state branch in Gwarzo local government area (LGA), to try to get data in order to assess the prevalence of hearing impairment in this community and in the long term to utilize this as a tool for planning and devising cost-effective public health hearing prevention programs.
Gwarzo LGA is one of the 44 LGA of Kano state, it covers an area of 393 km 2 with a population of 183,987 (population census-2006) within coordinates 11 0 55 ' N 7 0 56'E. Like Kano city, the major occupation of its inhabitants is petty trading/business on market days and subsistence farming.
It is worthy of note to emphasize that simple techniques to screen for hearing impairment such as the tuning fork can be an invaluable tool for hearing assessment. It is a noninvasive, qualitative test and combined with basic techniques of aural examination can help to detect persons with hearing loss. , We did not have the luxury of an audiometer, the only one available is located at the tertiary center some 60 km away in the state capital. From time immemorial, tuning forks have been used for screening for hearing impairment and determining to a variable extent the type of hearing loss and determining the need for referral.  The standard tuning fork used is the 512 and 256 Hz, these instruments may have their limitations and many have tried to evaluate their reliability. , Some of which are its unreliability in assessing degree of loss, subjectivity in interpretation, inaccuracy due to uncontrolled sound fields, variability in technique and most of all in children, ability to assess effect of hearing loss on speech.
The combinations of tuning forks have been found to improve the reliability of the Weber and Rinne test and recommended as an initial screening tool within a primary care setting to decide whether to refer for further care or audiometric testing. 
| Materials and Methods|| |
This was a cross-sectional population-based study carried out for a whole day in Gwarzo LGA of Kano state-Nigeria, by volunteer members of the NMA, Kano state branch, as part of its annual health week campaign in October 2010; the otologic evaluations were carried out by ENT specialists and senior trainees. A total of 650 patients were seen, out of which 37 had hearing impairment. This campaign was carried out after obtaining clearance from the local government chairman, the village head, and meetings with community elders by the health week organizing committee of the NMA and afterward announcements were made regularly via the news media (Radio) to the entire community a month prior to the date of the campaign.
All patients presenting with complaints of hearing impairment and other otologic complaints were promptly directed to the ENT consulting post and were usually escorted by a "significant other" for communication purposes. They all had a general physical examination and assessment of hearing via, conversational voice (CV: 45-60 dB loss) and loud voice (LV: 60-80 dB loss) while avoiding cues for lip-reading and masking the non-test ear, complimented with a tuning fork test. This was undertaken without initial otoscopy for removal of wax, otorrhea, or foreign body, as an initial testing according to WHO criteria. Afterward otoscopy was performed and intervention (such as aural toileting, foreign body, and wax removal) given where necessary. Ambient noise was kept to a minimum as physically allowed by locating the post in a remote section about 50 m from the main point of congregation. We did not have a sound-level meter or audiometer. Patients who do not know their cause of deafness but attributed it to a fever were labeled febrile illness/unknown.
For the purpose of hearing assessment during this survey, the population was divided into two groups, those below 15 years of age and those above, based on WHO, 2005 criteria. Hearing impairment for the purpose of this survey, was defined as any loss of hearing identified by patient or "significant others" enough to warrant repetitions of calls/command. Patients with a tympanic membrane perforation with or without ear discharge of greater than 12 weeks duration were labelled chronic suppurative otitis media (CSOM), while intact but thickened, dull/opalescent tympanic membrane or tympanic membranes with increased vascularity with or without fluid levels were tentatively labelled otitis media with effusion (no pneumatic/ Siegel's speculum, no tympanometry). Patients with ear discharge up to or less than 2 weeks were labelled acute suppurative otitis media and those with discharge in the range of 2-12 weeks as subacute otitis media. Testing children below 4 years of age may be cumbersome and rates of false negatives quite high; therefore, some modification of behavioural audiometry/distraction test was implemented.
Furthermore, our armamentarium also consisted of Jobson-Horne probes, battery- operated ENT headlights, generator-operated portable suction machine, a Heine mini 3000 otoscope, antiseptics (Savlon, etc.), otic agents (antibiotics, antifungals, and ceruminolytics/olive oil) cotton wool and gauze.
To assess hearing with the tuning fork if a patient cannot hear 512 Hz tuning fork-we assumed an approximate loss of 20-30 dB, on the contrary if they can hear 512 Hz tuning fork but not 256 Hz tuning fork-an approximate loss of 10-15 dB was inferred. The Weber and the Rinne's test was also performed with the 512 and 256 Hz tuning fork. The testing was initially explained to each patient and that it was not a painful or uncomfortable test before starting, Rinne's test was performed by gently knocking the tuning fork on a bony prominence and quickly holding it up beside the pinna approximately 2.5 cm away while keeping the prongs in-line with each other. Care was taken not to allow the fork make contact with the ear, to eliminate tactile response. Then the base of the still vibrating tuning fork is placed on the mastoid process, to transmit the sound through bone to the inner ear. The patient is then asked to say which sound is louder the 1st or the 2nd that is air or bone conduction respectively in the native dialect.
The Weber test was then carried out via the same approach of knocking the prongs on a bony prominence (in our case the elbow usually) and placing the base of the fork on the vertex or midline of forehead depending on response and thickness of hair. The patient is then asked which ear is the sound loudest or better heard. Where the 512 Hz detects lateralization, the 256 Hz is then used to further localize the finding. All those with a positive finding were referred to the tertiary center for further/proper evaluation via audiometry. A bus was made available for all those requiring further care with preferential treatment protocols in place at the hospital.
IBM SPSS (for windows, version 19) software was used to analyse this data. Using a confidence interval of 95% for judging significance, association between variables was explored with a two-tailed chi-square test. Prevalence rate was calculated manually.
| Results|| |
A total of 37 persons with hearing impairment were identified out of 650 seen in total giving a prevalence of 5.7% in Gwarzo LGA. Their ages ranged from 3 to 60 years with a mean of 27.4 years (+16.3 standard deviation). Seventy-eight point 4% were males (29) and 21.6% (8) females with a male: Female ratio of 3.6:1. The prevalence of hearing impairment in children below 15 years of age was 1.2%, while in adults it was 4.5%. Prevalence according to gender was equally 4.5% males and 1.2% females. Some patients responded equivocally to voice tests and were, therefore, further tested and typed with the tuning fork.
The commonest causes of hearing loss identified in this community were febrile illness/unknown, congenital/since birth, measles, meningitis, and ear infections with a frequency of 48.6% (18), 8.1% (3), 2.7% (1), 8.1% (3), and 32.4%(12), respectively [Figure 1].
|Figure 1: Spectrum of major causes of hearing impairment in the community|
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Infective and otoscopic findings seen in the community and contributing to severity of hearing loss were CSOM 18.9% (7), wax 16.2% (6), glue ear, and otomycosis had 2.7% (1), respectively. However, majority had apparently normal otoscopic findings 59.5% (22) [Figure 2].
|Figure 2: Profile of otologic disorders contributing to hearing impairment in the community|
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With the aid of the tuning fork, 48.6% (18) persons were predicted to have conductive hearing loss (CHL), 45.9% (17) with sensorineural hearing loss (SNHL) and only in 5.4% (2) persons was the tuning fork not heard at all [Figure 3]. Eight persons (21.6%) had unilateral hearing losses, while 29 (78.4%) had bilateral losses. There was a significant association between age and hearing loss, Fisher's exact test; P= 0.023. An attempt to find a relationship between type of loss and age groups showed no association, Fisher's exact test; P = 1.000.
|Figure 3: Tuning fork finding versus percentage of subjects found with different types of hearing loss|
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| Discussion|| |
Our study found a prevalence rate of 5.7% with more males being affected; the commonest cause of hearing loss was due to febrile illnesses followed by ear infections.
Despite the lack of trained manpower for epidemiological screening of hearing impairment in our setting, our study represents the first attempt to quantify and possibly reduce the disability associated with hearing loss and for intervention purposes as well.
While we recognize that audiological tests are the standards to diagnose hearing impairment, this requires testing the patient's ability to hear sound tones in a soundproof room with standardized equipment. These equipment's are expensive, require dedicated staff, time- consuming, and not widely available for mass screening especially in low-income settings such as ours. Our strength was in the resolve to use basic clinical skills/clinical manoeuvres to screen for hearing impairment and refer where necessary so that these patients get the much-needed treatment/rehabilitation after a population-based survey.
This study, however, has certain weaknesses. The non-availability of screening audiometer, the so called "lack of reliability" of the tuning fork test and voice test may all lead to poor standardization and reproducibility. Furthermore, our inability to utilize screening questionnaires (e.g., Hearing Handicap Inventory questionnaires) to measure social and emotional issues, and /or standardized (WHO) survey forms may also weaken the strength of this study. Similarly, the number of people seen may not reflect the actual number of people with disability and as such may not adequately represent the true situation. In addition to the above, since there is no survey without service, we were unable to provide free hearing aids to deserving patients outside of routine treatment due to lack of affordable hearing aids. We realized later that some patients could not maintain follow-up visits at the tertiary health center due to severe financial constraints and inability to take time off going to the farm/market.
Several studies have attempted to show the unreliability of the Weber and Rinne tests for general screening, , but in the study of Burkey et al., it was shown that in the Rinne test, sensitivity improved considerably when the test was performed by an otolaryngologist.  In our study, these tests were performed by trainee otolaryngologist and otolaryngologists. Each subject was tested thrice, first by the trainee then followed by two consultants consecutively, allowing for client exhaustion and inter-clinician variability, thereby increasing accuracy of the test.
Hearing loss is perhaps one of the most prevalent sensory disabilities all over the world. It is also the second most common cause of years lived with disability (YLD) accounting for 4.7% of the total YLD. It is estimated that the prevalence of hearing impairment in India is 6.3%,  while that of some states in Nigeria (Akwa Ibom, Benue, Katsina states) during a WHO survey in 2000 was found to be 6.2%.  Nigeria and India have a lot in common and in terms of population, poverty levels and general health indices both countries score may be at par. This probably accounts for why they have almost similar prevalence rates. In the African continent, the most recent survey carried out in Madagascar in 2004 revealed a prevalence of 29.9% of all types of hearing impairment and for disabling hearing impairment of 6.85%.  Against this background, our rate of 5.7% is not too far from the current prevalence rate on record for Katsina state in the North-western region of Nigeria, even though it appears low. This may be due to the fact that a larger sample size was used during the WHO survey compared to our study population (8975 vs. 37). Coincidently, the study area, Gwarzo LGA in Kano state, shares borders with Katsina state. Therefore, 5.7% prevalence rate in a single local government area is quite high compared to the value found for the whole of Katsina state. This may mean that hearing impairment has actually increased exponentially within a 10-year period (2000-2009).
Furthermore, these value were found to be quite low in countries with better health indices for ''disabling'' hearing impairment such as Saudi Arabia (0.9%-Riyadh 1988), Sweden (3.3%-1998), and the United Kingdom (3.9%-1980-1986.) However, the prevalence of mild or all types of hearing impairment is high for both Sweden and the UK, but because these are high- income countries these disabilities are easily identified and addressed appropriately.
With regard to age, from our study childhood onset of hearing loss was 1.2% this is about half of what was obtained with studies in India at 2%, while in adults our value of 4.5% is a far cry from 7.6% as recorded in India by Garg et al.,  However, according to the study of Stevens et al., the prevalence rate for the children in sub-Saharan Africa compares favorably with our value but adult-onset hearing impairment (15.7%) more than tripled our value (4.5%). This disparity may not be unrelated to the issue of sample size, availability of manpower, testing equipment, and so on. Some authors have posited that these high rates may be due to pre- and postnatal childhood infections such as meningitis, measles, rubella, and ototoxic drug use.  Similarly, our study showed a higher prevalence rate in men versus women as alluded to by Stevens report for sub-Saharan Africa.  This may also be attributed to factors such as more exposure of men to noise (noise-induced), trauma-related causes (occupational and motor vehicle accidents).
The study area lies in the meningitis belt where the risk of long-term disabling sequelae is highest as is also commonly seen in some low- and high-income countries. , The major causes of hearing loss in our study were febrile illnesses closely followed by ear infections, but due to low literacy levels and lack of qualified personnel for proper diagnosis, meningitis may actually rank higher than is depicted in [Figure 1]. Similarly, these health centres do not have proper patient records, and in those who have had recent illness may not present with classical neck stiffness to be documented as such. In addition, some patients who reported neck stiffness also allude to copious otorrhea preceding the neck stiffness (probable otogenic meningitis) thereby making it difficult to adequately place the patients. This was resolved by placing patients based on most probable identifiable cause of deafness. During this study, we could not establish causes due to ototoxicity.
While ear wax is usually reported as the commonest cause of reversible hearing impairment, our study revealed CSOM closely followed by ear wax [Figure 2]. ,, The Rinne, Weber, and voice tests were used successfully as a quick assessment of hearing acuity in our patient population despite the shortcomings of these tests. The predictive value of the tuning fork tests  was clearly depicted [Figure 4], where almost half (48.6%) of the sample population of all ages were diagnosed with conductive losses as described by Chole and Cook.  This also agrees with evidence that CHL in the form of glue ear (OME-otitis media with effusion) is commoner in children under 15 years of age. , Although Behn et al.,  argue that the overall accuracy of the Rinne and Weber tests in predicting CHL associated with OME in children is poor, most studies, however, agree that they were an invaluable tool for rapid hearing assessments. Furthermore, adult-onset SNHL is said to manifest as age increases this is our observation as well since the number rose sharply in the adult groups. See cluster bar chart [Figure 4]. Although, a lot of factors may have contributed to this such as genetic, nutritional, and ototoxic drug ingestion which were unfortunately not detected.
|Figure 4: Tuning fork findings versus age groups of subjects with childhood- or adult-onset hearing loss|
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We are aware that the tuning fork may have its limitations and their results can only be used as a quick guide for assessing the status of the hearing acuity of the ear which is what we set out to achieve at the outset, and this in combination with voice tests was used to successfully screen these patients. But we must emphasize that they cannot be used solely for screening purposes it may only act as a guide toward other audiological assessment.
Future areas of research/studies
Repeated prevalence studies and screening for hearing impairment is generally needed particularly in regions with high rates so that more accurate estimates of trends in hearing impairment can be made.
The voice test as a screening tool is simple and may be used in a primary care setting; although, accuracy may differ due to the different ways in conducting the test such as tester variability, therefore there is a need for standardization among clinicians so as to increase sensitivity especially in children.
| Conclusion|| |
Prevalence studies are lacking in developing countries, our study may have just scratched the surface by producing a figure of 5.7%. However, in the long term, we hope this study will help policy makers, the National Primary Healthcare Development Agency, Ministry of Health, non-governmental agencies appreciate the level of hearing impairment and take necessary actions toward preventive care with proper funding and formulation of policies geared toward primary ear and hearing care to help reduce the burden of hearing loss. This will in the long term make available statistics to help in providing cheap and affordable hearing aids to the needy.
There is no doubt whatsoever that more and better population-based surveys are required in order to determine hearing loss prevalence in the African subcontinent.
| Acknowledgement|| |
We are profoundly grateful to the entire community and all members of the NMA, Kano state branch that participated in the outreach program.
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Abdulazeez O Ahmed
Consultant ENT Surgeon/Hearing and Balance Disorders, P. O. Box 14529. Main Post Office, Kano
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]