The clinical assessment of "Obscure Auditory Dysfunction" (OAD) 2. Case control analysis of determining factors

Obscure Auditory Dysfunction (OAD) is defined as a clinical referral for self-reported auditory disability with no audiometric abnormality by stringent criteria. In stage 2 of a case control study of OAD, we have confirmed the general finding of stage 1 that OAD is multifactorial; compared with controls, patients as a group have a genuine performance deficit for understanding speech in noise, accompanied by personality-related factors. Paired logistic regression analysis optimally differentiated the 50 patients from their 50 matched controls on the basis of variables from three different domains: masked thresholds (psychoacoustic domain), dichotic listening ability (central/cognitive domain), and underestimation of own hearing ability (personality domain). A further and influential contributing variable was understanding of speech in noise supplementing the variables in both the psychoacoustic and the cognitive domains. With this model, 82.7% of the total group deviance was explained (i.e., the binary variable of case/control). A corresponding discriminant function analysis correctly classified 80% of patients and 90% of controls. When factors underlying the performance and personality-related variables were investigated with multiple linear regression within the two groups separately, relatively little of the within-group variance among OADs was explained. This is consistent with the multifactorial nature of OAD, in that the combinations of factors leading to OAD status differ between individuals. The research findings have been used to design a clinical test package to provide diagnostic information on the basis of OAD in individuals.