Validation of parameters for assessing Obscure Auditory Dysfunction—robustness of determinants of OAD status across samples and test methods

Abstract

About 5% of those presenting at an ENT clinic with ear or hearing complaints are found to have normal pure-tone thresholds. Many of this group complain specifically of difficulties understanding speech in background noise. We have termed this complaint 'Obscure Auditory Dysfunction' (OAD). Previous research on OAD (Saunders and Haggard, 1992) on a sample of 50 patients and 50 matched controls showed that 83% of the deviance (binary variance) in membership of group (OAD/control) could be explained by four variables, with three underlying factors. These four variables are performance threshold in noise for speech; discrepancy between this and a self-adjusted signal-to-noise ratio value (i.e. a measure of auditory confidence); dichotic listening performance; and performance on a psychoacoustic test, the threshold for detecting a tone in a spectrally notched noise. This paper reports a study on a further 59 new OAD patients and 64 unmatched controls, using the tests in the form present in the test package, plus certain others. For routine practice, slightly differing implementations of the auditory test techniques were used. Compared to the earlier sample, the new sample had poorer measures of speech reception threshold in noise and they considered themselves more handicapped by their OAD state; however there was no significant difference between the two samples on the other performance variables. Overall, the results demonstrate the robustness of the conclusions reached from the previous study, as the test-variable determinants of OAD status (i.e. case-control differences) were similar. The items on the OAD interview questionnaire which had shown significant differences between OADs and controls were also similar for the two OAD samples, giving a consistent picture of patient profile. These were: difficulties learning to read or write as a child (which relates to dichotic listening scores); adult ear problems; and tinnitus (which relate to the psychoacoustic scores). This necessary replication confirms the validity of the three-factor model of OAD status and the utility of the clinical test package based upon it.