By Harvey Abrams

In a recent MarkeTrak report, Kochkin and colleagues (2010) presented compelling evidence suggesting that the success of patients in real-world settings is directly correlated with the extent to which their hearing care provider adheres to a best-practice protocol for selecting and fitting hearing aids. This protocol, as outlined in clinical practice guideline documents such as those from the American Academy of Audiology (AAA, 2006), emphasizes two fundamental elements: verification and validation. However, clinicians often face confusion regarding the distinction between these two aspects. Simply put, verification focuses on the device itself, while validation takes into account the patient’s perspective.

Understanding the Verification Process

Verification involves assessing the extent to which a hearing aid meets specific measurable specifications or expectations. One aspect of verification is measuring the hearing aid’s response in a test chamber (known as the coupler response) to ensure that it aligns well with the manufacturer’s specifications. This process serves as a quality control measure, ensuring that the received device matches the intended specifications.

Another crucial component of verification is the probe-tube measurement battery, which evaluates whether the hearing aid achieves the predetermined gain or output levels (targets) when measured in the ear canal. Since different ears can exhibit distinct frequency/gain characteristics, it is imperative to measure the hearing aid response in real-time in the actual ear to obtain an accurate assessment of its gain and output characteristics.

However, it is important to note that real-ear verification procedures extend beyond mere target matching. Additional aspects to consider include verifying that the hearing aid’s output does not exceed the patient’s discomfort level, ensuring that compression operates as intended, confirming that directional performance meets expectations, validating the effectiveness of the feedback-cancellation algorithm, and assessing the proper functioning of noise reduction capabilities.

It is worth mentioning that not all verification measures need to be performed in the ear. For instance, pediatric audiologists often fit the hearing aid in the coupler after determining the discrepancy between the coupler’s response and the child’s ear canal response (referred to as the real-ear-to-coupler difference or RECD). In such cases, only one measure—the real-ear unaided response—needs to be obtained in the ear, while the remaining verification measures can be conducted in the test chamber, providing relief for both the child and the audiologist.

However, achieving a close match between the real-ear target and the hearing aid response in fitting software does not necessarily guarantee a fully verified fitting. While such software-based targets are based on average ear canal responses and predicted hearing aid responses, individual variations can lead to over- or under-amplification at specific frequencies, resulting in insufficient audibility, compromised sound quality, or uncomfortable loudness.

Understanding the Validation Process

Validation, in contrast, focuses on assessing the patient’s perception of treatment success. It entails measuring the extent to which treatment goals have been achieved from the patient’s perspective. Various validation tools are available, although they may not all measure the same aspects. Indirect validation measures, such as the Hearing Handicap for the Elderly (HHIE) and the Abbreviated Profile of Hearing Aid Benefit (APHAB), gauge perceived benefit but may not fully capture the relative importance patients attribute to specific communication situations described in the questionnaires.

Direct validation measures, such as the Client Oriented Scale of Improvement (COSI) or Glasgow Hearing Aid Benefit Profile (GHABP), are designed to identify the communication situations that cause the most frustration for patients and those they are most eager to resolve. By assessing the extent to which these critical situations are perceived as resolved following treatment, these measures provide validation of the relative success of the intervention. Treatment goals may encompass interventions beyond amplification, such as assistive technology, auditory training, or group hearing rehabilitation.

While measures of aided speech recognition in quiet and noise can offer patient-specific benefit information, they do not necessarily indicate the resolution of real-world communication difficulties. While in-clinic performance measures, such as speech recognition improvement in quiet or noise (e.g., the Hearing in Noise Test), are valuable, they do not comprehensively validate the success of treatment.

The Essential Role of Verification and Validation

In summary, both verification and validation play pivotal roles in a best-practice protocol for selecting and fitting hearing aids. Verification ensures that the device meets specifications and functions as intended, while validation takes into account the patient’s perspective and perception of treatment success. By adhering to a comprehensive protocol that incorporates both verification and validation, hearing care providers can maximize the likelihood of achieving successful treatment outcomes for their patients.

Harvey Abrams, PhD, is the Director of Audiology Research at Starkey Laboratories. Previously, Dr. Abrams served in clinical, research, and administrative capacities with the Department of Veterans Affairs and the Department of Defense. He also teaches distance-learning courses for the University of South Florida and University of Florida.  He received his master’s and doctoral degrees at  the University of Florida. His research has focused on treatment efficacy and improved quality of life associated with audiologic intervention. He has authored and co-authored several recent papers and book chapters and frequently lectures on outcome measures, health-related quality of life, and evidence-based audiologic practice.

REFERENCES

• American Academy of Audiology (2006): Guidelines for the audiological management of adult    hearing   impairment. Audiol Today 18:32-36.
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