Confidence limits of word identification scores derived using nonlinear quantile regression

The relation between degree of sensorineural hearing loss and maximum speech identification scores (PB_max) is commonly used in audiological diagnosis and rehabilitation. It is important to consider the relation between the degree of hearing loss and the lower boundary of PB_max, as the PB_max varies largely between subjects at a given degree of hearing loss. The present study determines the lower boundary by estimating the lower limit of the one-tailed 95% confidence limit (CL) for a Dantale I, word list, in a large group of young and older subjects with primarily sensorineural hearing loss. PB_max scores were measured using Dantale I, at 30 dB above the speech reception threshold or at the most comfortable level from 1,961 subjects with a wide range of pure-tone averages. A nonlinear quantile regression approach was applied to determine the lower boundary (95% CL) of PB_max scores. At a specific pure-tone average, if the measured PB_max is poorer than the lower boundary (95% CL) of PB_max, it may be considered disproportionately poor.