Development and Evaluation of a Language-Independent Test of Auditory Discrimination for Referrals for Cochlear Implant Candidacy Assessment

Objectives: The purpose of this study was to (1) develop a Language-independent Test of Auditory Discrimination (LIT-AD) between speech sounds so that people with hearing loss who derive limited speech perception benefits from hearing aids (HAs) may be identified for consideration of cochlear implantation and (2) examine the relationship between the scores for the new discrimination test and those of a standard sentence test for adults wearing either HAs or cochlear implants (CIs).

Design: The test measures the ability of the listener to correctly discriminate pairs of nonsense syllables, presented as sequential triplets in an odd-one-out format, implemented as a game-based software tool for self-administration using a tablet computer. Stage 1 included first a review of phonemic inventories in the 40 most common languages in the world to select the consonants and vowels. Second, discrimination testing of 50 users of CIs at several signal to noise ratios (SNRs) was carried out to generate psychometric functions. These were used to calculate the corrections in SNR for each consonant-pair and vowel combination required to equalize difficulty across items. Third, all items were individually equalized in difficulty and the overall difficulty set. Stage 2 involved the validation of the LIT-AD in English-speaking listeners by comparing discrimination scores with performance in a standard sentence test. Forty-one users of HAs and 40 users of CIs were assessed. Correlation analyses were conducted to examine test-retest reliability and the relationship between performance in the two tests. Multiple regression analyses were used to examine the relationship between demographic characteristics and performance in the LIT-AD. The scores of the CI users were used to estimate the probability of superior performance with CIs for a non-CI user having a given LIT-AD score and duration of hearing loss.

Results: The LIT-AD comprises 81 pairs of vowel-consonant-vowel syllables that were equalized in difficulty to discriminate. The test can be self-administered on a tablet computer, and it takes about 10 min to complete. The software automatically scores the responses and gives an overall score and a list of confusable items as output. There was good test-retest reliability. On average, higher LIT-AD discrimination scores were associated with better sentence perception for users of HAs (r = -0.54, p <0.001) and users of CIs (r = -0.73, p <0.001). The probability of superior performance with CIs for a certain LIT-AD score was estimated, after allowing for the effect of duration of hearing loss.

Conclusions: The LIT-AD could increase access to CIs by screening for those who obtain limited benefits from HAs to facilitate timely referrals for CI candidacy evaluation. The test results can be used to provide patients and professionals with practical information about the probability of potential benefits for speech perception from cochlear implantation. The test will need to be evaluated for speakers of languages other than English to facilitate adoption in different countries.