Factors affecting outcomes on the TEN (SPL) test in adults with hearing loss

Recent work using the Threshold Equalizing Noise (TEN) test as a gold standard suggests that the presence of cochlear dead regions in persons with moderate-to-severe hearing loss may be quite common. In addition, previous data suggest that certain characteristics of hearing loss, such as severe-profound high-frequency hearing loss or steeply sloping configurations may be more commonly associated with positive TEN findings. These findings, however, are based largely on studies including a relatively small number of participants and/or participants that were included based on specific audiometric criteria (e.g., the presence of severe high-frequency hearing loss). Likewise, results from many of these studies are limited to the frequency regions of 500-4000 Hz. There has been less work that has systematically evaluated the relationship between audiometric characteristics and TEN test findings, particularly in the frequency regions above 4000 Hz, on a large number of individuals with a wide range of hearing losses and hearing loss configurations.

The purpose of this study was to further examine the effects of audiometric characteristics such as degree and slope of hearing loss on the rate of positive, negative, and inconclusive findings on the TEN test over a wide frequency range (250-8000 Hz). Given that the functional impact of positive findings (i.e., findings suggestive of a dead region) may vary with the extent of potential damage, we were also interested in determining the relative occurrence of "patchy" versus contiguous positive findings on the TEN.

Fifty-nine adults (117 ears) with a wide range of SNHL participated. To examine results over a wide frequency range (250-8000 Hz), the TEN (SPL), rather than the TEN (HL), was utilized. Thresholds, in both ears, were measured in quiet and in the TEN (SPL). Results were categorized as positive (suggestive of a dead region), negative (not suggestive of a dead region), or inconclusive.

Consistent with past research, positive TEN (SPL) results were more common when hearing losses exceeded 60 dB HL; however, there was not a systematic increase in positive results with increases in threshold. In contrast to previous work, however, positive test results among individuals with milder hearing losses (< 60 dB HL) were not uncommon, suggesting a potential for false positive results. In regard to audiometric slope, also consistent with past research, slope of hearing loss was an inadequate predictor of TEN (SPL) results. Negative results (not suggestive of a dead region) were less common in participants with steeply sloping losses while positive test findings were unaffected by hearing loss slope. Although a large proportion of participants had positive results on the TEN (SPL), for most participants, these positive findings occurred in isolated (i.e., one or two frequencies) rather than in contiguous frequency regions.

The relatively large number of inconclusive results and the potential for false positive results makes interpreting the functional impact of TEN (SPL) results difficult, particularly when positive results are in the high (> 4000 Hz) frequencies. In addition, although a large proportion (84%) of study participants had positive findings on the TEN (SPL), the functional impact of these findings is not clear as, in the majority of cases, positive findings occurred at only one or two test frequencies.