1Department of Veteran Affairs Black Hills Healthcare System, Vermillion, South Dakota

2College of Arts and Sciences, University of South Dakota, Vermillion, South Dakota

Prior to the fitting of hearing aids, clinicians and patients must discuss the best treatment options for the physical and audiologic needs of the patients. To be able to confidently make these decisions, the clinician should complete a medical and audiological case history. Additionally, clinicians need accurate results from a comprehensive audiologic evaluation. The evaluation should include the following: pure-tone testing, word recognition testing, speech-in-noise testing, and loudness discomfort level measures. This article will outline the process and procedures for acquiring this information in line with the Audiology Practice Standards Organization (APSO) Guidelines for Adult Hearing Aid Fittings Standards 1 and 4. This article will also discuss how results can affect decision-making during the hearing aid selection and fitting process.

The completion of a comprehensive audiologic evaluation is the initial step that a clinician must take when beginning the hearing aid selection and fitting process and is part of the Audiology Practice Standards Organization (APSO) Guidelines for Adult Hearing Aid Fitting Standards 1 and 4. This evaluation will guide clinicians in their clinical decision-making. Furthermore, the comprehensive evaluation determines whether or not a patient would be an appropriate candidate for hearing aids or if that patient's needs would be better suited by other technology, such as a cochlear implant ( editor's note : a comprehensive evaluation which may include other tests, e.g., tympanometry, will be conducted for the purpose of differential diagnosis to ensure the patient is guided to medical treatment when necessary or appropriate). In this article, the components of a comprehensive evaluation will be discussed. These components include the case history, pure-tone air-conduction, pure-tone bone-conduction, and word recognition testing. In addition, the importance of completing speech in noise testing and measuring loudness discomfort levels will be discussed. Each aspect of the comprehensive audiologic evaluation is critical in the hearing aid selection and fitting process. These tests should be completed in a sound booth, as it is standard practice to ensure a proper testing environment.

Throughout the process of obtaining a case history, clinicians can build significant rapport with their patients and begin to determine the specific hearing needs of their patients. 1 In addition, this initial interaction can foster trust between the clinician and the patient. This can enhance patient care and result in improved outcomes because the patient's thoughts and opinions are valued, and the patient sees engagement from the clinician, which increases their feeling of being valued. When interacting with patients, clinicians must focus on the effectiveness of their communication. This can be accomplished by actively listening to patients and their families, utilizing open-ended questions, and pausing while waiting for the patient to respond. These methods also allow for the development of patient-centered care.

In the initial consultation, the reason for the visit should be determined. 2 This will allow the clinician to determine the expectations of the patient. Furthermore, clinicians can use this time to gather information on the patient's lifestyle, needs, and motivation level, as patient preferences are an influential aspect of the hearing aid selection process. 3 The patient's dexterity level and visual acuity need to be taken into consideration. Clinicians should also determine what type of telephone a patient primarily utilizes as that can impact what type of hearing aid is pursued. All of the information obtained will then influence the hearing aid selection process.

For instance, an in-the-ear style hearing aid will be easier for patients with dexterity concerns to use and maintain than a completely-in-the-canal, behind-the-ear, or receiver-in-the-canal style hearing aid. 4 In addition, clinicians should note which hearing aids may be easier for patients to use, maintain, and clean. Patients who are more motivated and accepting of pursuing amplification will be more satisfied with hearing aids than patients who are not. Patients who have positive attitudes toward amplification tend to use their hearing aids full-time when compared with patients who have a negative outlook on hearing aids. These examples demonstrate why clinicians must always be aware of their patients' needs and expectations.

In addition to building rapport with patients, the clinical consultation is essential in obtaining information regarding a patient's medical history. All information obtained from a patient during the case history must be critically analyzed, as the case history is one factor that helps determine an appropriate diagnosis for the patient. 2 Information regarding possible hearing loss, tinnitus, dizziness, balance issues, otalgia, otologic drainage, aural pressure or fullness, otologic surgery, and history of excessive noise exposure should be obtained from the patient. This information will help the clinician determine whether or not a patient has indicators for any of the “red flags” that may warrant a medical referral. The following statements in Fig. 1 are considered “red flags” for possible ear disease by the Food and Drug Administration (FDA). 5

FDA “red flags” for hearing loss.

In addition to the “red flags” created by the FDA, the American Academy of Otolaryngology—Head and Neck Surgery (AAO-HNS) also has developed a list of “red flags.” 6 The statements in Fig. 2 are considered “red flags” by AAO-HNS.

AAO-HNS “red flags” for hearing loss.

If a patient has any of these “red flags,” the provider should recommend that the patient be medically evaluated by a physician to determine if there is an underlying disease of the ear that needs to be addressed prior to that individual pursuing amplification. It is important to note that medical clearance by a physician is no longer required by the FDA prior to the purchasing of hearing aids. 5 As a result, clinicians must use their best judgment and know when to refer to a physician when an ear disease is suspected. To assist patients and clinicians in identifying a possible ear disease, self-administered questionnaires that examine the “red flags” for ear disease have been developed. 7 These questionnaires can be extremely beneficial for providers in communities where specialty physicians, audiologists, or hearing instrument specialists are not present. 8 If left untreated, ear diseases can have long-term consequences for patients, which is why clinicians must take all steps necessary to identify these “red flags” and ensure that proper follow-up actions are taken. 9

Prior to any testing, otoscopy should be completed in both ears. Clinicians should determine if a foreign body, active drainage, or a visible abnormality is present in the external auditory canals. 5 6 If cerumen is noted and the clinician is comfortable, cerumen management should be performed. If the clinician detects a foreign body that is unable to be removed or active drainage, a referral to an appropriate provider should be made. If the tympanic membrane appears abnormal, it should be extensively documented. If warranted, the provider should make a referral.

During otoscopy, clinicians should make note of the size and shape of the patient's external auditory canal, as it can influence the style of hearing aid pursued. 3 For instance, a custom style hearing aid may not be feasible for a patient with an extremely narrow external auditory canal. Any malformations of the pinna should also be documented. Depending on the malformation of the pinna, that patient may not be an appropriate candidate for a behind-the-ear or receiver-in-the-canal style hearing aid. Once otoscopy has been performed and the external auditory canals are free of debris, pure-tone air conduction testing can begin.

Pure-tone air conduction testing could be considered one of the most important aspects of a comprehensive audiologic evaluation. It is performed to determine the softest level at which an individual responds to a stimuli 50% of the time, which is also known as a threshold. 2 Pure-tone air conduction testing examines the entire auditory pathway. These thresholds indicate the hearing sensitivity of an individual. Pure-tone audiometry typically assesses the frequency range from 500 to 8,000 Hz. Given that current evidence-based hearing aid fitting algorithms use HL threshold data converted to SPL threshold data as input to the formulae, threshold data are essential to a hearing aid fitting. In a comprehensive audiologic assessment, the following frequencies should be examined: 250, 500, 1,000, 2,000, 4,000, 6,000, and 8,000 Hz. If there is a difference of greater than 15 dB HL between 500 and 1,000 Hz or 1,000 and 2,000 Hz, then the frequencies of 750 and 1,500 Hz should also be tested.

It is recommended that pure-tone air-conduction testing be completed using supra-aural earphones or insert earphones. Pure-tone air conduction testing should be completed in the patient's better ear first as that will determine the need for masking in the poorer ear. When the initial threshold search has begun, clinicians should either begin well below threshold or with a suprathreshold tone. 10 Pure-tones can be presented in a pulsed or manual presentation. If using a manual presentation, the tone should be presented for 1 to 2 seconds. It is important to note that pulsed tones are favored over manual presentation, as pulsed tones are preferred by patients and help them differentiate between the presented stimulus and their possible tinnitus. 11 Thresholds are then obtained using a modified method-of-limits procedure. 2 Clinicians need to mask thresholds whenever masking is indicated (i.e., cross hearing can be perceived by the non-test ear).

Bone-conduction testing is another component of a comprehensive audiologic assessment that needs to be performed prior to the hearing aid selection process. Bone-conduction testing is completed by placing a bone vibrator on the skull, which then stimulates the cochlea directly through vibration. 2 Bone-conduction testing bypasses both the outer ear and middle ear. It is recommended that mastoid placement be used with the bone-vibrator, as it results in lower thresholds than forehead placement. 12 Bone-conduction thresholds should be obtained at several frequencies. The following frequencies are the most common frequencies that bone-conduction thresholds are measured at: 500, 1,000, 2,000, and 4,000 Hz. 10 A threshold also can be obtained at 3,000 Hz as needed. If indicated, appropriate masking for these thresholds should be used to obtain accurate ear-specific thresholds. Bone-conduction thresholds are obtained in the same manner as air-conduction thresholds.

Once bone-conduction testing has been completed, the site-of-lesion or etiology of a hearing loss can be determined. 2 If air-conduction thresholds are elevated and bone-conduction thresholds are in the normal hearing sensitivity range, an individual has a conductive hearing loss. If both air-conduction and bone-conduction thresholds are elevated but within 10 dB HL of each other, an individual has sensorineural hearing loss. If both air-conduction and bone-conduction thresholds are elevated but bone-conduction thresholds are 15 dB HL or lower than air-conduction thresholds, an individual has a mixed hearing loss. If a conductive component is present, the clinician should make a referral to a physician prior to the discussion of amplification options as medical treatment may be warranted. 5 Clinicians also can use other audiologic tests to help confirm the results of pure-tone air-conduction and bone-conduction testing. If a conductive component is present, one may want to consider performing tympanometry or acoustic reflex threshold testing. 2 This will help clinicians determine specific diagnoses and confirm the need for a referral to a physician.

The results of pure-tone testing will have a significant impact on the hearing aid selection process. For instance, clinicians can use the results of pure-tone air-conduction and bone-conduction testing to determine the strength of receiver required for an individual's hearing loss. 13 Clinicians can use the results of pure-tone testing to determine the coupling method for behind-the-ear or receiver-in-the-canal style hearing aids. Additionally, an individual with normal hearing sensitivity through the low- to mid-frequencies will likely not prefer the sound quality of a style of hearing aid that creates occlusion. Individuals with this type of hearing loss typically find more benefit from an open fit hearing aid. If an earmold or custom hearing aid is chosen for this type of patient, the earmold or custom hearing aid should have a larger vent to help reduce the effects of occlusion. Furthermore, an individual with profound hearing loss would not be appropriate candidate for a completely-in-the-canal style of hearing aid. Behind-the-ear hearing aids with earmolds would be more appropriate for this type of patient as long as the patient benefits from the device. If a patient does not find benefit from traditional amplification, other technologies, such as a cochlear implant, should be pursued. As a result, clinicians must be specific and intentional with their recommendations during the hearing aid selection process. The recommendations given can impact on an individual's success with hearing aids, and possibly his or her satisfaction with hearing aids.

Speech audiometry is another important aspect of a comprehensive audiologic evaluation. The two primary types of speech audiometry include speech recognition thresholds (SRTs) and word recognition testing. 2 A SRT is the softest level that a spondaic word can be repeated back 50% of the time. A spondaic word consists of two syllables that have equal stress. 14 An SRT should be obtained for each ear during the evaluation. 2 Masking for SRTs must be completed when appropriate. SRTs can be obtained and used as a cross-check principle for the pure-tone average of air-conduction testing to help clinicians ensure accurate results. In addition, SRT then assists clinicians in determining the level at which word recognition testing should be completed.

Word recognition testing is completed at suprathreshold levels and a score is determined using the percent of words correct. 2 This test is completed to determine how well an individual can understand speech in a quiet environment. Word recognition testing is typically completed 30 to 40 dB above the SRT. However, research by Mueller and Hornsby suggests that the presentation level should be based on the threshold obtained at 2,000 Hz. 15 Fig. 3 displays the decibel sensation level (dB SL) values that clinicians can use for presentation levels using the 2,000-Hz threshold.

Decibel sensation level (dB SL) values that clinicians can use for presentation levels using the 2,000-Hz threshold.

Clinicians should remember that word recognition testing should be completed at a level that is loud enough to obtain a maximum possible score. This level is extremely variable between individuals and can be dependent on the wordlists used. 2 In addition, the completion of word recognition testing at multiple levels will help determine a better estimation of the maximum possible score. The most common stimuli used for word recognition testing are monosyllabic words. Clinicians should administer word recognition testing in accordance with the protocol of the specific test that is used. Word recognition testing can assist clinicians in making decision when selecting amplification. 15 If a patient has asymmetrical word recognition scores, a traditional hearing aid may not be beneficial for the ear that has the poor word recognition score. 13 In cases of asymmetric hearing loss that warrant unilateral amplification, a contralateral routing of signal (CROS) system may be recommended if bilateral hearing is not beneficial. This helps the patient overcome the head shadow effect that would have attenuated sounds from the unaided side and get better access to auditory information in their environment. While word recognition testing in quiet provides information for clinical decision-making, performance in complex listening situations is also important.

Research suggests that hearing and understanding conversations in challenging listening environments is one of the primary complaints of individuals who have hearing loss. 16 Speech in noise testing is one method by which clinicians can evaluate an individual's ability to understanding speech when background noise is present. However, it is important to note that speech in noise testing should only be completed if appropriate. Patients who have poor word recognition scores in quiet will subsequently have poor scores for speech in noise testing. As a result, speech in noise testing may not be indicated for these individuals.

For those cases where speech in noise testing is deemed to be appropriate, standardized test materials should be utilized. 17 The protocols for those tests need to be followed to ensure that the test is administered in an appropriate manner. Some examples of speech in noise tests that clinicians can choose from included the following:

Speech in noise testing should be initially completed unaided as it allows for a baseline measurement. 17 Once an individual is fit with hearing aids, speech in noise testing can be completed again to help determine a level of improvement. In addition, speech in noise testing may assist clinicians when making gain adjustments on hearing aids. 27 For instance, low-frequency gain may be decreased, and high-frequency gain may be increased for patients who score low on aided speech in noise testing. The results of both unaided and aided speech in noise testing can assist clinicians in establishing realistic expectations with hearing aids for patients. 17 27 Hearing aid benefit and user satisfaction may increase as a result of the additional counseling provided on realistic expectations with hearing aids.

The measurement of loudness discomfort levels has been a part of the hearing aid selection and fitting process for many years. 28 Loudness discomfort levels (LDLs) can be used clinically to measure the highest end of the auditory dynamic range. 29 During the hearing aid fitting process, the patient's dynamic range is utilized to fit the devices by ensuring that the sound is audible, but not too loud. 30 Individuals with hearing loss typically have a higher level of discomfort than individuals with normal hearing. However, LDLs can vary significantly among individuals with hearing loss. 28 Clinicians must acknowledge that specific, unaided LDL measurements must be completed with every patient and average LDLs cannot be used among patients for the hearing aid fitting process.

LDLs can be measured using various different methods. An absolute estimate of loudness discomfort can be obtained by instructing patients to press a handheld response button when the presented signal becomes uncomfortable. 29 The initial presentation level of the stimulus is typically between 60 and 70 dB HL (decibels hearing level) when utilizing this method. The stimulus is increased by 5 dB HL until the patient reports that the sound has become uncomfortably loud. A relative estimate of loudness discomfort can be obtained by using the Contour Test. 31 With the Contour Test, subjects rate different sound levels according to the following seven categories of loudness: (1) very soft; (2) soft; (3) comfortable, but slightly soft; (4) comfortable; (5) comfortable, but slightly loud; (6) loud, but okay; and (7) uncomfortably loud. During this method, the stimulus is initially presented at 20 dB HL and increased in 5-dB HL increments until the patient rates the stimulus as “uncomfortably loud,” or a category 7 rating. 29 31

Both of these methods yield statistically comparable results in the same listeners. 29 As a result, both methods can be utilized to appropriately determine LDLs, as each method is effective and reliable. Research by Mueller and Bentler suggests that these frequency-specific LDL measurements can then be utilized when determining the maximum power output levels of hearing aids. 28 When LDLs are used in the fitting process, patients require fewer programming adjustments. 27 In addition, patient satisfaction with hearing aids remains more stable over time.

The basis of hearing loss management is the audiologic evaluation and is why they are the Standards 1 and 4 of the APSO Guidelines for Adult Hearing Aid Fittings. When clinicians have access to complete and accurate results, they have the information needed to counsel patients and their families. In addition, it allows clinicians and patients to begin the process of aural (re)habilitation. There are various decisions by clinicians and patients that affect the hearing aid selection process. Recognizing these decisions is essential in providing exceptional service that leads to positive patient outcomes. Audiologists should always strive to complete comprehensive audiologic evaluations in accordance with best practices and current standards.

Conflict of Interest None declared.