Feb 2019 The Hearing Journal
Clinical evaluation of hearing is often focused on hearing sensitivity despite evidence showing that depressed sensitivity alone does not reflect everyday listening and communication difficulties. Assessment of auditory processing should be encouraged, along with the education of audiologists, in providing a more comprehensive evaluation.
BEYOND PURE TONE AUDIOGRAM
The pure tone audiogram remains the gold standard of hearing evaluation despite its limitations. While the audiogram is the primary tool for determining the type, degree, and configuration of hearing loss, this measure does not provide information beyond hearing sensitivity to a limited range of frequencies:
1 It does not reveal the physiological state of the entire (peripheral and central) auditory system (the auditory nerve included) nor the complete physiological state of the cochlea. Auditory neuropathy provides a well-known example of the disconnect between the pure tone audiogram and auditory processing.
2 The audiogram explains only a small part of the variance in speech understanding performance and self-reported hearing ability of neurologically normal older adults.
3 Moreover, adults with central auditory nervous system (CANS) pathology (e.g., due to stroke, traumatic brain injury, degenerative disease) and children with auditory processing disorder (APD) and learning problems present with difficulty understanding speech in noise or competing message environments despite normal pure tone audiograms.
GOLD STANDARDS FOR APD AND HEARING LOSS
The gold standard for the diagnosis of a disorder is defined as the best available evidence-based methodology for diagnosis. Current clinical practice guidelines depend on the use of test batteries due to the inherent complexity of any given disorder. This enables a more accurate diagnosis.
The auditory processing test battery approach is the best available gold standard approach to APD diagnosis. Moreover, there are several parallels between this APD gold standard and pure tone audiogram as the gold standard for diagnosing hearing loss, including (1) the subjective nature of testing, (2) results dependent on the clinician's ability to elicit behavioural responses that reflect an individual's true auditory ability, and (3) the need for the test results to be interpreted within the context of medical history to arrive at a conclusion regarding an individual's “hearing” status. Pure tone audiometry results may not always agree with objective (i.e., electroacoustic or electrophysiological) audiological tests, yet this does not lead to questioning the pure tone audiogram as a gold standard for determining hearing sensitivity and hearing loss. The same logic and standard apply to clinically used auditory processing testing. In addition, all behavioural tests impose a degree of cognitive load, including attention, executive function, and working memory.
