Development and evaluation of a New Zealand Digit Triplet Test for auditory screening.

Abstract

The aim of this study was to develop a Digit Triplet Test (DTT) using NZ English. The DTT is a hearing screening tool that uses spoken numbers presented in background noise to estimate speech recognition thresholds (SRTn). The NZ DTT will be made available via telephone or the internet, and will provide each person who completes the screening test with information about whether they should seek a professional hearing assessment. Normal-hearing participants (22 listeners) with hearing thresholds ≤20 dB HL were tested to establish the intelligibility of the individual digits at various signal-to-noise ratios (-20; -17.5; -15.0; -12.5; -10.0; -7.5; and -5.0 dB). The mid-points of the resulting psychometric functions were then used to adjust the level of each digit to achieve the same intelligibility. A SRT of -10.40 ± 1.75 dB SNR for the broadband presentation was established for the separate ear triplet test with the average slope of 17.3%/dB ± 3.9 %/dB for the ten test lists generated. The binaural ear DTT results were compared to best ear threshold PTA and found to have a highly significant correlation (r = 0.816, p<0.001) and a significant correlation to the QuickSIN sentence-in-noise test (r = 0.668, p<0.001). The binaural triplet test was found to have a sensitivity of 100% and specificity of 85%. The separate ear DTT results were compared to the best ear threshold pure tone audiometry and found to have a highly significant correlation (r = 0.809, p<0.001). The separate ear triplet test was found to have a sensitivity of 88% and specificity of 81% (1 – specificity = 0.187). The internet version of the DTT hearing screening test will provide New Zealanders with an easily accessible and objective test that will raise awareness about hearing and hopefully reduce the length of time people take before seeking advice about their hearing.