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.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.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. Shows an example of a TS audiometer user interface. 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, 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. 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.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. 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. 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, 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. 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. Another study 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, 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. 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. 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 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. Elevated sensitivity and specificity values avoid the occurrence of false negatives and false positives, respectively.
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However, it must be remembered that no procedure is entirely accurate, i.e., no procedure has a sensitivity and specificity equal to 100%. 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. 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%. 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.
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Automatic hearing screening conducted with a low cost audiometer and a circumaural phone showed a sensitivity of 100% and a specificity of 49%. 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. 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% and 56% and 43%, respectively.