First-language raters' opinions when validating word recordings for a newly developed speech reception threshold test

The validity of an isiZulu speech reception threshold test for use with adult isiZulu speakers

Background

This study continued the development of an isiZulu speech reception threshold (zSRT) test for use with first language, adult speakers of isiZulu.

Objectives

The objective of this study was to determine the convergent and concurrent validity of the zSRT test.

Methods

One hundred adult isiZulu first-language speakers with normal hearing and 76 first-language, adult isiZulu speakers with conductive or sensorineural hearing losses ranging from mild to severe were assessed on pure tone audiometry and a newly developed isiZulu SRT test. Convergent validity was established through agreement of the zSRT scores with pure tone average (PTA) scores. Concurrent validity was assessed by examining the steepness of the psychometric curve for each word in the zSRT test for each type and degree of hearing loss.

Results

Intraclass correlation coefficient analyses showed zSRT scores were in substantial to very high agreement with PTA scores for the normal hearing and hearing loss groups (NH – right ear ICC consistency = 0.78, left ear ICC = 0.67; HL – right ear ICC consistency = 0.97, left ear ICC consistency = 0.95). The mean psychometric slope (%/dB) at 50% correct perception for all words in the zSRT test was 4.92%/dB for the mild conductive hearing loss group, 5.26%/dB for the moderate conductive hearing loss group, 2.85%/dB for the moderately severe sensorineural hearing loss group and 2.47%/dB for the severe sensorineural hearing loss group. These slopes were appropriate for the degree of hearing loss observed in each group.

Conclusion

The zSRT test showed convergent and concurrent validity for assessing SRT in first language, adult speakers of isiZulu.

The internal and external consistency of a speech reception threshold test for isiZulu speakers with normal hearing sensitivity

Background and objectives

This study investigated reliability, particularly the internal and external consistency, of a new isiZulu speech reception threshold (SRT) test.

Methods

To examine internal consistency, 21 adult isiZulu speakers with normal hearing sensitivity completed the SRT test using the first and second halves of the SRT wordlist in the same test session. To examine external consistency, a separate 23 adult isiZulu speakers with normal hearing sensitivity completed the SRT test, using the whole word list on two occasions 4 weeks apart. Consistency of SRT test scores in these test conditions was measured using intraclass correlation coefficient analyses (a measure of the consistency or reproducibility of different observations of the same quantity) and Bland and Altman analyses of agreement (a comparison of measurement error with the expected variation amongst subjects).

Results

Intraclass correlation coefficient values ranged from 0.69 to 0.79, showing the isiZulu test scores were highly consistent between the test and retest conditions used in this study. Bland and Altman analyses showed that isiZulu speakers with normal hearing sensitivity can be expected to return isiZulu SRT test scores that differ by no more than 7.5 dB HL – 8.7 dB HL between original and repeat assessments.

Conclusion

The isiZulu SRT test was reliable, showing high internal and external consistency, when used to assess first-language speakers of isiZulu with normal hearing sensitivity. These findings warrant continued development of the isiZulu SRT test for eventual clinical use. This development should include validating this test on first-language speakers of isiZulu with and without hearing loss.