The Effect of Mild Hearing Impairment on Auditory Processing Tests

The application of auditory processing tests to patients with sensorineural hearing loss is controversial. Several studies have shown that it is difficult to separate peripheral from central hearing processes. In the present study, a Dutch auditory processing test battery was administered to 24 subjects with mild, relatively flat, symmetrical sensorineural hearing loss. Tests were administered twice; the second time, the presentation level in four out of the six tests was adjusted according to the speech reception threshold. The scores of the hearing-impaired subjects were significantly poorer than those of the subjects with normal hearing on five out of the six tests, even with the adjusted presentation level. Significant correlations were found between test scores and PTA (pure-tone average); scores on words-in-noise, filtered-speech and binaural-fusion tests were additionally corrected according to PTA. In contrast to previous studies in the literature, the present dichotic-digit and pattern-recognition tests were greatly influenced by mild hearing loss. Therefore, this auditory processing test battery cannot readily be used to diagnose central auditory processing disorders in patients with flat sensorineural hearing loss. At least, both adjustment of presentation level and additional correction are needed.