USE OF TEST-RETEST MEASURES TO EVALUATE PERFORMANCE STABILITY IN ADULTS WITH COCHLEAR IMPLANTS

Objective: This study was designed to evaluate performance stability w ith test-retest measures of electrical thresholds, electrical maximum acceptable loudness levels, sound-field thresholds, and audition-only speech tests. The hypothesis was that the standard error of measuremen t differs from one individual to another for each test, and therefore test-retest measures need to be obtained from each subject. Design: Te st-retest data were obtained in three sets. For the first two sets, da ta were obtained over 4 successive weeks to determine day-to day varia bility. The third set was obtained on 2 successive days, 2 to 10 month s later at each subject's annual evaluation. The seven subjects were r ecipients of the Nucleus cochlear implant and used the Mini Speech Pro cessor at least one year. They were selected because they were availab le for research testing. Results: The ranges of electrical thresholds and maximum acceptable loudness levels obtained from each subject duri ng the first two sets were substantially larger on some electrodes tha n on others. Between set 1 and set 2 for each subject, there were sign ificant differences between thresholds and between maximum acceptable loudness levels on some electrodes. For thresholds as well as maximum acceptable loudness levels, the standard error of measurement across t he three sets and 10 electrodes differed among subjects. The group sta ndard error of measurement for sound-field thresholds was small (2 dB) . The group standard error of measurement for the NU-6 word test score d according to phonemes (2.75%) was less than half that for the vowel (6.06%) and consonant (5.67%) tests. The standard error of measurement for each speech test differed among subjects. Conclusions: The standa rd error of measurement for thresholds as well as maximum acceptable l oudness levels varies among electrodes in the same subject and among s ubjects across electrodes. The standard error of measurement also vari es among speech tests for the group as well, as among subjects for eac h speech test. There is little variation in test-retest measures of so und-field thresholds among subjects, These results suggest the clinica l importance of obtaining test-retest measures for evaluating the stab ility of electrical thresholds, electrical maximum acceptable loudness levels, and speech tests.