Accuracy of Manufacturer First Fittings
Beck and Duffy (2007) reported that "the only way to know what’s really going on in the ear canal is to measure it!" They reported that real-ear measures (in 2007) were only used in only one of four fittings, and, based on Aarts and Caffee "less than 12 percent of the predicted REARs were comparable to actual REARs."
Recently, 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 concluded that the "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."
Aazh et al (2012) reported the accuracy of manufacturers "first-fit" initial fittings prescribed by NAL-NL1 across 51 initial fittings from 30 consecutive patients (10 female, 20 male, mean age 67 years, 21 people fitted bilaterally). They note, the rationale of NAL-NL1 is to maximize speech intelligibility and to keep loudness at normal (or below normal) levels.
Of the 51 fittings, 36 (71 percent) failed to come within 10 dB of the NAL-NL1 real ear insertion gain (REIG) target at one or more frequencies between 250 and 4000 Hz using the "first-fit" prescription. Aazh et al concluded that "when the manufacturer’s software was used to program the open-fit hearing aids…71 percent of the first fittings failed to achieve a match within +/- 10 dB…of the target…" at one or more frequencies between 250 and 4000 Hz..
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.
Aazh H, Moore BCJ, Prasher D. (2012) The Accuracy of Matching Target Insertion Gains With Open-Fit Hearing Aids. American Journal of Audiology 21:175-180.
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.