Prediction of speech discrimination scores from audiometric data.

Data routinely collected in audiological evaluations were used to predict speech discrimination scores in patients with varying degrees of sensorineural hearing loss. Puretone threshold at 2000 Hz and age squared (age') gave the best prediction in the stepwise multiple regression analysis. Slope of the hearing loss did not aid in the prediction. Expected speech discrimination scores for patients with mild-to-severe hearing losses in the age range from 14 to 94 are included, and their use is discussed. Because a disproportionately low speech discrimination score relative to threshold sensitivity may indicate a retrocochlear lesion (e.g., Refs. 9, 11, and 24), its occurrence alerts the audiologist to the need for further site of lesion tests. As hearing loss increases, speech discrimination scores generally decrease, both for flat and sloping audiometric configurations (e.g., Refs. 2, 13, 16, 30). However, there are no objective criteria for determining whether an individual speech discrimination score is poorer than would be predicted from the audiogram. Although past attempts to predict speech discrimination scores from pure-tone audibility thresholds have met with limited success (7, 8, 20, 22, 25, 26, 29, 33), the generalization that retrocochlear disorders may result in disproportionately low speech discrimination scores is used by audiologists in the interpretation of test results. Presumably, each audiologist has learned through experience what range of speech discrimination scores would be expected to occur with a particular audiogram. We decided to attempt once again to quantify the relationship between speech discrimination scores and other information routinely obtained in an audiological evaluation for patients presumably having a cochlear hearing loss using word lists and test procedures typical of many medical settings. In these settings, the adult patients range in age from young to geriatric and have sensorineural hearing losses resulting from a wide variety of etiologies. Speech discrimination ability usually is measured with W-22 word lists using a monitored live voice presentation rather than tape-recorded test materials (23), and in large hospital settings, audiological evaluations are obtained by several audiologists. Our study differs from previous research in patient selection (age and etiology) and method and level of administration of the speech discrimination tests. The parameters in previous studies have been reviewed by Noble (27). The purpose of this study was to answer two questions. First, how well can speech discrimination scores be predicted from pure-tone thresholds, slope of hearing loss, speech reception threshold (SRT), and age? Second, which of these variables are most important for the best prediction of speech discrimination scores? These questions were investigated in two different analyses using multiple regression techniques. In our first analysis, we determined how well speech discrimination scores could be predicted for our sample of 136 patients based on their thresholds at 500, 1000,2000, and 4000 Hz, slope of loss, SRT, and age. This analysis allowed us to eliminate some of the predictor variables. A smaller set of predictor variables was used in our second analysis and determined how well speech discrimination scores could be predicted for a sample of 774 patients.