Keywords Hearing - Hearing Loss - Hearing Tests
Introduction
Hearing loss is among the three most prevalent conditions worldwide, with around 636.5
million people suffering from a certain degree of hearing loss[1 ]. It is estimated that in Brazil, 6.8% of the population suffers from disabling hearing
loss, i.e., a hearing threshold level for the better ear of 41 dB HL or greater, averaged
at frequencies of 0.5, 1, 2, and 4 kHz. Of these individuals, 5.3% are children between
4 and 9 years old, 36.2% are elderly, and 19.5% are adults between 20 and 59 years
old[2 ]. In the state of São Paulo, a population-based study showed that the prevalence
of hearing loss was 44%, being higher for elderly male individuals[3 ]. A population-based cross-sectional study performed in Rio de Janeiro showed that,
for the elderly, the prevalence of hearing loss in the better ear was 42.9%[4 ].
Hearing loss can hinder or even impede acquisition and development of oral language,
as well as academic and social development in children. In addition, it can decrease
the quality of life and work and educational opportunities of adult individuals. This
condition also has an impact on society in terms of loss of productivity of affected
individuals as well as costs of treatment, education, and rehabilitation of people
with special needs. Thus, healthcare actions focused on prevention, early identification,
and treatment of hearing problems also have social and economic implications.
The Brazilian National Health System (Sistema Único de Saúde, SUS) has incorporated
the treatment of the hearing impaired in previous decades. Such action was supplemented
by the establishment of the National Hearing Healthcare Policy in 2004[5 ] and, more recently, by the Care Network for People with Disabilities within the
SUS[6 ]. This network is organized into the components of primary care, specialized rehabilitation
care, and emergency hospital care. Primary care services are provided through Healthcare
Basic Units (UBS), which prioritize certain strategic actions intended to enhance
access for and attention to people with disabilities, including the promotion of early
identification services.
In Brazil, newborn universal hearing screening has been enforced by law since 2010[7 ]. However, progressive or late onset hearing losses are not detected at birth. It
is estimated that 9–10 out of 1000 school aged children have permanent hearing loss
in at least one ear[8 ]. The Health in School Program (PSE), initiated in 2007 as a joint action between
the Ministries of Health and Education, aims to incorporate the school community into
projects and programs that make use of healthcare and education in order to comprehensively
deal with the issues that compromise the development of Brazilian children and teenagers.
The primary task of the PSE is the assessment of the health condition of students,
including hearing status. In order to do so, audiometric procedures, among others,
are recommended[9 ].
For adults and the elderly, hearing loss onset is often insidious, complicating self-perception
of the problem and, consequently, the request for treatment. Performing hearing screening
in this population would enable timely identification and corresponding referral to
rehabilitation services, in order to minimize secondary consequences such as functional
decline, depression, and social isolation.
In Brazil, there are still no large scale hearing screening programs targeting school
aged children, adults, and the elderly. When screenings are conducted in this population,
they are isolated events. The reasons for this scenario are multifactorial and include
the costs of the procedure. The related costs can be attributed to the cost of the
professional performing the procedure, the necessary time to perform it, and the cost
of the necessary equipment. In order to decrease screening costs, a simple, fast,
and effective method using low cost equipment that can be easily operated by a primary
care professional must be utilized[10 ].
It is also necessary to emphasize the difficulty of access to hearing health for populations
living far from urban centers. Thus, a relevant aspect of this scenario is the development
of computer-based systems that can be used in telehealth models. Different low cost
systems for conducting audiometric screening[11 ]
[12 ]
[13 ] or audiological assessment at distance (14-15) have been published in the literature.
Such systems use TDH-39 supra-aural headphones or ER3A insert phones, which can increase
device cost. One study was found on the use of a software-based screening audiometer
that utilized a conventional circumaural phone with a 3.5 mm plug. However, this system
was automatic and hearing responses were queried with 3 dB increments, making the
test relatively lengthy with a duration of about 15 minutes (10).
The Telessaúde (TS) audiometer was developed to perform audiometric screening using
off-the-shelf USB interface headphones. This characteristic has a relevant impact
on acquisition and replacement costs (the prototype costs less than 50 USD) and also
facilitates access of the user to the TS audiometer. A wide variety of USB headphones
are available and the user can chose a model that is considered more convenient, once
that set of headphones has been calibrated for use with the TS audiometer. The fact
that only off-the-shelf electronic devices are used also facilitates the availability
of the TS audiometer, as the eventual manufacturer will not require a specific infrastructure
for manufacturing and distribution. The aim of this study was to evaluate the TS audiometer
for use during audiometric screening.
Method
This randomized prospective study was conducted in the Speech Language Pathology and
Audiology Clinic of the X School, University X, and was approved by the relevant research
ethics committee (process number 021/2010). This clinic is currently accredited by
the SUS as a tertiary hearing healthcare service.
Once an informed consent form was signed by 60 individuals, aged 18 years or older,
they were voluntarily enrolled in the study and segregated into 2 groups ([Table 1 ]):
Group A: for this group, employees and graduate students of the Bauru School of Dentistry
were invited to participate in the study. This group was composed of 30 adults with
age varying from 18 to 41 years old. None of these individuals presented a hearing
complaint.
Group B: for this group, individuals who had ENT or audiological complaints and were
referred to the clinic were invited to participate in the study. This group was comprised
of 30 individuals with age ranging from 23 to 85 years old. There were 12 adults and
18 elderly subjects (aged 60 years or older). None of these individual had had their
hearing assessed previously.
Table 1.
Demographic data of the participants.
Group
Number of ears tested
Age in years (mean ± SD)
Gender
Complaint
Male
Female
Tinnitus
Dizziness
Hearing difficulty
A (n = 30)
60
23.2 ± 5.6
26
4
—-
—-
—-
B (n = 30)
60
59 ± 18.2
16
14
11
3
18
The TS audiometer is integrated by software developed in Visual Basic.NET 2005 (Net
Framework 2.0) for Windows XP and a set of USB headphones. It is supported by a multiuser
database system managed by an administrator. The system can store the registration
information of the location where screening is performed, the information of the healthcare
professionals (users) and screened populations, as well as the corresponding evaluation
results. [Figure 1 ] shows an example of a TS audiometer user interface.
Figure 1. TS audiometer user interface.
With regards to hardware, the audiometer uses a Microsoft LifeChat LX-3000 headset
with the following specifications: (a) bilateral earphones (20 Hz–20 kHz); (b) embedded
microphone (100 Hz–10 kHz); (c) embedded USB sound board with 16 bit precision; (d)
plug and play , i.e., no other software installation is needed for normal use; and (e) incorporated
volume control. As for every USB device, the headset is identified by the host computer
by its Vendor ID and Product ID, therefore allowing the software to apply the corresponding
calibration parameter or impede the performance of the audiometric procedure if the
corresponding parameters are not available.
Following FDA recommendations for signature of electronic records [16 ], the identity and electronic signature of the healthcare professional are protected
by a password only known and modifiable by the healthcare professional. Additionally,
a change control, or audit trail, is not deemed necessary, as once they are electronically
signed, the assessment results can no longer be modified.
In this study, the TS audiometer was installed and tested in an ASUS EeePc900 laptop,
given its relatively low cost and portability. This laptop has a 8.9" screen, a Celeron
M353 processor, a 4 GB hard drive, 1 GB of DDR II RAM, an Intel UMA video board, a
1.3 megapixel webcam, a Windows® XP operating system, 802.11b/g WLAN, USB/VGA/Earphone/Mic/Network inputs/outputs,
embedded loudspeakers, a battery autonomy of approximately 2.5 hours, dimensions of
22.5 × 17 × 2 cm, and a weight of 0.99 kg.
The TS audiometer includes a calibration user interface. This interface is only accessible
for the testing prototype. Through this interface, the calibration parameters of a
certain headset model can be determined and stored. These values are stored in the
system parameters database and they are used every time an audiometric screening is
performed. The device (computer and headphones) was calibrated by an engineer with
experience in conventional audiometer calibration according to the applicable requirements
of the standard project ABNT/CB 03/CE-03:029.01-022/1. The frequencies 250–8000 Hz
were used to calibrate the left and right earphones of the Microsoft LifeChat LX-3000
headset. During calibration, the TS audiometer software was used to provide acoustic
stimulation. With regard to the calibration, it must be noted that the USB headset
included its own sound board, i.e., its own analog and digital input/output stages.
Therefore, the calibration parameters were characteristic of the headset model and
independent of the host computer model or type. The frequencies 250, 500, 1000, 2000,
3000, 4000, 6000, and 8000 Hz were calibrated ranging from 10 dB HL (minimum stimulation
level) to 70 dB HL (maximum stimulation level) in 5 dB steps for both the right and
left channels.
Another feature contemplated during development of the TS audiometer was the real-time
estimation of ambient noise levels during performance of the screening procedure.
As audiometric screening is not necessarily conducted in an audiometric booth or an
acoustically prepared room, the TS audiometer uses the microphone embedded in the
headset, placed in the upright position, to determine the ambient noise level. The
software application converts the sampled noise level into a dB scale in order to
assess if the real-time ambient noise level allows screening to be performed. The
system will automatically display a message to the evaluator when the ambient noise
level is greater than 60 dB SPL to make him/her aware that minimization of noise level
is desirable. The system user interface will flag the responses obtained under an
ambient noise level greater than 60 dB SPL and also stores the average ambient noise
level measured during an evaluation on its database. This is intended to minimize
the occurrence of false positives induced by the lack of an appropriate acoustic environment.
As the screenings were conducted in a sound booth, this feature of the TS audiometer
was not evaluated in the present study.
Audiometric screening was conducted in groups A and B with 2 different pieces of equipment:
the SD 50 audiometer (Siemens) coupled with supra-aural THD-39 headphones and the
TS audiometer. The screenings were conducted on the same day by 2 different audiologists,
each one operating one audiometer. The audiologists did not share the results obtained
with each other and they were not aware of the patients' hearing complaints. The procedures
were conducted in a randomized order.
Audiometric screening was based on the ASHA protocol[17 ]. Pure tones at frequencies of 500, 1000, 2000, and 4000 Hz were presented at a 25 dB
HL level. The participant was instructed to raise his/her hand each time the acoustic
stimuli were heard. In the audiometric screening, a “pass” result was considered when
the subject responded to the stimuli presented. The result was considered “fail” when
the subject did not respond to one or more stimuli presented in one or both ears.
Following audiometric screening, and regardless of the result (pass or fail), all
participants underwent otologic inspection, pure-tone threshold audiometry, and speech
audiometry procedures. For such purposes, SD 50 (Siemens) or Midimate 622 (Madsen)
audiometers were used. Air conduction hearing thresholds were obtained with TDH-39
earphones for the inter-octaves of the frequencies between 250 and 8000 Hz, for both
ears. When the air conduction hearing thresholds were greater than 20 dB HL, bone
conduction audiometry was also performed for the frequencies 500, 1000, 2000, 3000,
and 4000 Hz.
Hearing thresholds were determined by applying the ascendant-descendant strategy.
At each pure-tone detection response, the presentation level was reduced by 10 dB
until the individual no longer responded to the stimuli. Then, the presentation level
was increased in 5 dB steps until a response was detected. The hearing threshold,
at each frequency, was the lowest level at which the individual could detect 50% of
the stimuli presented.
All procedures were performed in a sound booth, where the noise levels were within
the specified ranges of the ANSI 1999 standard [18 ].
Concordance analysis and Cohen's kappa coefficient were used to analyze the screening
results between the conventional and TS audiometers for groups A and B.
The precision of the TS audiometer screening instrument was evaluated through specificity,
sensitivity, positive predictive value, and negative predictive value analysis. The
sensitivity was defined as the percentage of ears that failed screening with the TS
audiometer among those in which hearing loss was observed with pure-tone threshold
audiometry. The specificity was defined as the percentage of ears that passed screening
among those with normal hearing results. In this study, air conduction audiometric
thresholds less than or equal to 20 dB HL were considered as normal hearing. The positive
and negative predictive values were defined as the probability of a patient having
hearing loss if they failed screening and the probability of a patient having normal
hearing if they passing screening, respectively.
Results
With regard to group B, the number of individuals that failed the screening was 27
with the TS audiometer and 26 with the conventional audiometer.
Within group B, 4 participants presented normal hearing at all frequencies. The other
26 participants presented different degrees of sensorineural hearing loss ([Figure 2 ]), as per the pure-tone and speech audiometry results.
Figure 2. Mean and standard deviation of audiometric thresholds for participants who presented
hearing loss (n = 26).
Discusion
In group A ([Table 2 ]), all tested ears passed the screening. Although the sample size was limited, this
observation is supported by the fact that the participants were predominantly young
females, a population for which the prevalence of hearing loss is smaller [2 ]
[3 ]. The concordance between the screening results obtained with the conventional and
TS audiometers was excellent.
Table 2.
Audiometric screening and concordance results for group A (n = 60 ears).
Frequency (Hz)
TS audiometer
Conventional audiometer
Concordance (%)
Pass
Fail
Pass
Fail
500
60
0
60
0
100
1000
60
0
60
0
100
2000
60
0
60
0
100
4000
60
0
60
0
100
Total (%)
240 (100)
0 (100)
240 (100)
0 (100)
100
In group B ([Table 3 ]), most ears failed the screening with both audiometers. It is worth noting that
this group of participants had some kind of otologic complaint, with 18 of them reporting
hearing difficulties. This group was also mostly composed of elderly subjects, for
whom a greater prevalence of hearing loss is observed [2 ]
[3 ]
[4 ]. Thus, a considerable number of failures were expected.
Table 3.
Audiometric screening and concordance results for group B (n = 60 ears).
Frequency (Hz)
TS audiometer
Conventional audiometer
Concordance (%)
Kappa coefficient
Pass
Fail
Pass
Fail
500
32
28
32
28
98.31
0.97
1000
24
36
28
32
93.33
0.86
2000
20
40
22
38
96.67
0.93
4000
06
54
10
50
96.33
0.71
Total (%)
82 (34.2)
158 (65.8)
92 (38.3)
148 (61.4)
96.67
0.84
The number of failures at the frequency of 500 Hz was less than that for the other
frequencies, which contradicts results reported in the literature [10 ]. This can be explained by the fact that the screening was conducted in a sound booth,
this being a limitation for the generalization of the data from the current study.
In fact, hearing screening is generally conducted in a non-acoustically isolated room.
Consequently, ambient noise can exert a masking effect over emitted signals, which
is more significant at low frequencies, thus affecting screening results at these
frequencies. For this reason, several screening protocols exclude the 500 Hz test,
although this frequency is relevant for the assessment of the impact of middle ear
condition on hearing sensitivity.
In [Table 3 ], the kappa coefficients show an excellent concordance between the evaluators for
the screening results obtained with the conventional and TS audiometers at the frequencies
of 500 Hz to 3000 Hz, and substantial concordance for the frequency of 4000 Hz [19 ]. The inter-evaluator reliability allows verification of the degree of correspondence
between the independent evaluations of 2 or more evaluators classifying the same phenomena.
Therefore, it is a relevant indicator of the quality of the screening procedure with
the TS audiometer. Previously, kappa coefficients of 0.79–0.93 were observed when
evaluating the concordance between audiometric screenings conducted with a portable
audiometer and a conventional audiometer[20 ]. Another study[10 ] indicated a kappa coefficient of 0.20 between screening performed with a software-based
audiometer and a conventional one. The fact that this result is lower than the one
obtained in the current study could be related to the population characteristics (school
aged children) and the impact of ambient noise at the frequency of 500 Hz, since when
this was excluded from the analysis, a kappa value of 0.62 was obtained. Another important
difference is that an automatic screening procedure was employed in the previous study,
in contrast with the conventional procedure utilized in the current study.
In [Table 4 ], it can be observed that audiometric thresholds for group A were within normal values.
Audiometric thresholds greater than 25 dB HL were found for at least one frequency
in 65.4% of the ears tested in group B. For this group, 26 participants (86.6%) presented
sensorineural hearing loss, with a greater involvement of the high frequencies ([Figure 2 ]). This high incidence of hearing loss is due to the fact that the participants of
this group were recruited from a specialized hearing healthcare clinic. It is relevant
to note that all of the subjects who presented hearing loss underwent a complete audiological
assessment and received corresponding treatment, including fitting of hearing aids.
Table 4.
Distribution of the number of ears with normal thresholds and hearing loss in both
groups.
Frequency (Hz)
Group A (n = 60 ears)
Group B (n = 60 ears)
Normal
Hearing loss
Normal
Hearing loss
500
60
0
29
31
1000
60
0
29
31
2000
60
0
19
41
4000
60
0
6
54
Total (%)
240 (100)
0 (0)
83 (34.6)
157 (65.4)
Pure-tone audiometry is currently the gold standard for assessment of hearing sensitivity.
Therefore, the sensitivity and specificity of the screening procedures with the conventional
and TS audiometers ([Table 5 ]) were calculated using the results obtained with pure-tone threshold audiometry
as a reference. It was not possible to calculate the sensitivity of the procedures
for group A due to the fact that none of the participants failed the screening or
presented hearing loss with pure-tone audiometry. The specificity of this group equaled
100% for both procedures. For group B, the sensitivity and specificity values of the
TS audiometer were similar to those of the conventional audiometer ([Table 5 ]). Elevated sensitivity and specificity values avoid the occurrence of false negatives
and false positives, respectively. However, it must be remembered that no procedure
is entirely accurate, i.e., no procedure has a sensitivity and specificity equal to
100%.
Table 5.
Specificity, sensitivity, positive predictive value, and negative predictive value
for TS and conventional audiometers.
Audiometer
Group
Sensitivity
Specificity
Predictive value
Positive
Negative
TS
A
——
100%
——
100%
B
95.5%
90.4%
94.9%
91.5%
Conventional
A
——
100%
——
100%
B
91.1%
94%
96.6%
84.8%
The sensitivity and specificity values of the TS audiometer were similar to those
found in the literature. The sensitivity and specificity of a portable screening audiometer
were reported to be 91.8–98.5% and 88.0–96.3%, respectively[20 ]. Studies involving the Audioscope device with pure-tone sweep (500 to 4000 Hz) for
hearing screening demonstrated a sensitivity of 94–97% and a specificity of 69–80%[11 ]. With regards to affordable audiometers, the TS audiometer presented higher sensitivity
and specificity values than those found in the literature. Sensitivity and specificity
values of 86.7% and 75.9% were verified with a remote automatic audiometric screening
method (20 dB HL pure-tone sweep), based on the use of a computer and TDH-39 earphones
[13 ]. Automatic hearing screening conducted with a low cost audiometer and a circumaural
phone showed a sensitivity of 100% and a specificity of 49% [10 ]. The differences observed between the literature and the present study can be related
to the stimuli loudness level applied in the current study (25 dB HL), attenuation
differences in the earphones utilized, and, mainly, the screening method (automatic
vs. manual) and screening room acoustics (non-acoustically isolated room vs. audiometric
booth) used.
Under operational conditions (field application), the performance indicators of a
test procedure are modified by the frequency of occurrence of a medical condition
within the population (prevalence). Therefore, the predictive value of the procedure
has a significant relevance, i.e., the probability of occurrence of a medical condition
given a positive or negative result. In the current study, the positive and negative
predictive values of the TS audiometer were equal to 94.9% and 91.5%, respectively,
being similar to those obtained with a conventional audiometer ([Table 5 ]). This means that if a subject fails screening with the TS audiometer, there is
a 94.9% chance of them actually suffering from hearing loss and a 5.1% (100 - 94.9)
chance of them having normal hearing. If the subject passes screening, there is 91.5%
chance of them having normal hearing and an 8.5% (100 - 91.5) chance of them having
hearing loss.
For group B, the observed predictive values of the TS audiometer were greater than
those found in the literature for other affordable audiometers, which presented positive
and negative predictive values of 48.1% and 95.7%[13 ] and 56% and 43%[10 ], respectively. These findings are justified by the differences observed in the sensitivity
and specificity of the TS audiometer when compared to other audiometers, and the fact
that the screened population was from a specialized hearing healthcare clinic, where
a higher number of subjects with hearing loss were registered.
Screening programs are justified if there is evidence that sustains 3 standard criteria:
(a) negative consequences of the medical condition must be sufficiently significant
in order to justify the screening effort; (b) an effective treatment for the detected
medical condition is available; and (c) an accurate, practical, and convenient screening
test is available[11 ]. Although this study is limited by the number of participants, the results obtained
suggest that the TS audiometer meets the necessary criteria for a screening procedure.
Conclusion
The specificity, sensitivity, and positive and negative predictive values of audiometric
screening conducted with the TS audiometer were high and similar to those obtained
with a conventional audiometer.
