Question
What are the most popular methods used to calculate ''percentage of hearing loss?'' Please give examples
Answer
Usually, what is estimated in hearing loss compensation cases is called
''hearing handicap'' (HH) or ''binaural hearing impairment'' (BHI or BI) with
the basic concept being interference with activities of daily living, especially speech communication. Since the 1950's, most states and federal
agencies that award compensation calculate HH from the pure-tone audiogram. At first, this was considered a temporary or stopgap measure, assuming that speech tests, using words or sentences, would soon be developed to the point that they would predict self-reported HH better than pure-tone tests could. Fifty years later, we are still using the audiogram for this purpose, because speech testing has proved disappointing.
The 1959 AMA method used the pure-tone average of thresholds at 0.5, 1, and 2 kHz. If that average was less than 15 dB HL in both ears(25 dB after conversion to ISO/ANSI calibration), HH was zero. For every dB above 15 (now 25), HH increased by 1.5%, reaching a maximum at 82 (now 92)dB. If the two ears had unequal pure-tone averages, HH was calculated by a weighted average giving the better ear 5 times the weight of the worse ear. The AMA modified their method in 1979 to add 3 kHz. Most states use or permit the 1979 AMA method, a few use the 1959 method, and some have their own idiosyncratic formulas.
Here is an example of HH calculated by the 1979 AMA method:
Right (better ear) impairment = 1.5(30-25) = 7.5%
Left (worse ear) impairment = 1.5(40-25) = 22.5%
HH (or BI) =
5/6(7.5%) + 1/6(22.5%) = 10%
A more complete discussion of the history, validity, and use of these and
other methods can be found in Chapter 5 (Impairment and Handicap) of Medical Legal Evaluation of Hearing Loss, 2nd edition, 2001, Singular Thomson Learning.
BIO:
Robert A. Dobie, M.D., is Director, Division of Extramural research,
National Institute on Deafness and Other Communication Disorders, in
Bethesda Maryland. He completed medical school and residency in otolaryngology at Stanford University, as well as fellowships in neuro-otology (University of Zurich) and auditory neurophysiology (LSU Medical School). A former president of the Association for Research in Otolaryngology, he has published over 100 papers; the second edition of his book, Medical-Legal Evaluation of Hearing Loss, has recently (March 2001)been published by Singular/Delmar Thomson Learning.
