Comparing First Fit and Verified Hearing Aid Prescriptions
Beck and Duffy (2007) reported that real-ear probe microphone measures (REM) represent the only objective measure of sound between the medial end of the hearing aid and the tympanic membrane. Unfortunately, they also reported that REMs are only used in (approximately) one of four hearing aid fittings. With regard to the accuracy of measured REMs versus predicted (i.e., "first fit") responses, Beck and Duffy noted that Aarts and Caffee reported on 41 subjects and their characterization that "less than 12 percent of the predicted REARs were comparable to actual REARs." Aarts and Caffee further stated that it is inappropriate to use predicted REARs (based on their observations) as the basis of individual hearing aid fittings. Beck and Duffy reported that "the only way to know what’s really going on in the ear canal is to measure it!"
Abrams et al (2012) reported that "While it is evident that the initial fit approach consistently fails to approximate the prescribed response as verified with a probe microphone, the question remains, does it matter?" They evaluated 22 experienced hearing aid users via the Abbreviated Profile of Hearing Aid Benefit (APHAB, Cox and Alexander, 1995) while comparing "predicted" (i.e., "first fit") to "verified" (probe-microphone measured responses) NAL-NL1 prescriptions. To evaluate the differences, half the subjects were fit with new hearing aids using the predicted fitting and half were fit using the verified fitting. Some 4 to 6 weeks later, initial APHAB results were acquired and the fittings were reversed. After a second 4 to 6 week period, a second APHAB result was acquired.
In essence, with regard to the APHABs three subscales (Ease of Communication, Reverberation and Background Noise), a statistically significant greater benefit was obtained using the verified protocol. With regard to the APHABs fourth subscale (aversiveness), the same trend was true (greater benefit was obtained using the verified protocol), although this subscale measure did not reach statistical significance. Finally, 15 of the 22 subjects preferred the sounds of their hearing aids programmed to the verified prescription. Abrams et al concluded "clinical use of a verified prescription does matter as it will likely yield better self-perceived hearing aid fitting outcomes than currently available initial-fit approaches."
For More Information, References, and Recommendations
Aarts NL, Caffee CS. (2005) The Accuracy and Clinical Usefulness of Manufacturer Predicted REAR Values in Adult Hearing Aid Fittings. Hearing Review 12(12):16-22.
Abrams HB, Chisolm TH, McManus M, McArdle R. (2012) Initial Fit Approach Versus Verified Prescription- Comparing Self-Perceived Hearing Aid Benefit. Journal of the American Academy of Audiology 23:768-778.
Beck DL, Duffy J. (2007) Visible Speech – A Patient-Centered Clinical Tool. Hearing Review.
Cox RM, Alexander GC. (1995) The Abbreviated Profile of Hearing Aid Benefit. Ear & Hearing 16:176-186.