誘発反応聴力測定における反応域値の決定について

抄録

The most rational procedure of determining response threshold in evoked response audiometry (ERA) is to estimate the stimulus intensity level, with which 50 per cent positive resposes (ED₅₀) can be obtained. In order to measure ED₅₀ efficiently with a small number of experiments, simplified up-and-down method (UDM) by Brownlee et al. was applied and its validity in ERA was investigated. Up-and-down method was first described by Dixon and Mood in 1947. It is a sequential procedure in which the stimulus level of any trial is determined by the preceding stimuli and responses.
1. Variability of threshold values obtained from UDM (a chip experiment)
On the basis of average rates of positive responses as a function of stimulus intensity in normal and hard-of-hearing children, a chip experiment of UDM was carried out to estimate response threshold of both groups. In normal children 85-97% of the estimated thresholds ranged between 20 and 50 dB, while in impaired children 91 -98% lay within a limit of 70dB±10 dB.
2. Determination of thresholds in ERA with UDM
Response thresholds in ERA were measured by using UDM in 3 young children during sleep and their testing processes were presented in detail.
3. Comparison of thresholds obtained from ERA and COR or play audiometry
Thresholds of ERA for young children determined with UDM were compared with those obtained from COR or play audiometry. Thirty-nine pairs of thresholds in 22 young children were used for the comparison. In normal or slightly impaired children, the mean threshold of ERA was about 10 dB higher than that of behavioral tests, whereas in severely impaired children the mean threshold of both tests almost coincided with each other