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.