Test-Retest Reliability and Minimal Detectable Change of Randomized Dichotic Digits in Learning-Disabled Children: Implications for Dichotic Listening Training.

Abstract

Evaluation of dichotic listening to digits is a common part of many studies for diagnosis and managing auditory processing disorders in children. Previous researchers have verified test-retest relative reliability of dichotic digits results in normal children and adults. However, detecting intervention-related changes in the ear scores after dichotic listening training requires information regarding trial-to-trial typical variation of individual ear scores that is estimated using indices of absolute reliability. Previous studies have not addressed absolute reliability of dichotic listening results. To compare the results of the Persian randomized dichotic digits test (PRDDT) and its relative and absolute indices of reliability between typical achieving (TA) and learning-disabled (LD) children. A repeated measures observational study. Fifteen LD children were recruited from a previously performed study with age range of 7-12 yr. The control group consisted of 15 TA schoolchildren with age range of 8-11 yr. The Persian randomized dichotic digits test was administered on the children under free recall condition in two test sessions 7-12 days apart. We compared the average of the ear scores and ear advantage between TA and LD children. Relative indices of reliability included Pearson's correlation and intraclass correlation (ICC2,1) coefficients and absolute reliability was evaluated by calculation of standard error of measurement (SEM) and minimal detectable change (MDC) using the raw ear scores. The Pearson correlation coefficient indicated that in both groups of children the ear scores of test and retest sessions were strongly and positively (greater than +0.8) correlated. The ear scores showed excellent ICC coefficient of consistency (0.78-0.82) and fair to excellent ICC coefficient of absolute agreement (0.62-0.74) in TA children and excellent ICC coefficients of consistency and absolute agreement in LD children (0.76-0.87). SEM and SEM% of the ear scores in TA children were 1.46 and 1.44% for the right ear and 4.68 and 5.47% for the left ear. SEM and SEM% of the ear scores in LD children were 4.55 and 5.88% for the right ear to 7.56 and 12.81% for the left ear. MDC and MDC% of the ear scores in TA children varied from 4.03 and 3.99% for the right ear to 12.93 and 15.13% for the left ear. MDC and MDC% of the ear scores in LD children varied from 12.57 and 16.25% for the right ear to 20.89 and 35.39% for the left ear. The LD children indicated test-retest relative reliability as high as TA children in the ear scores measured by PRDDT. However, within-subject variations of the ear scores calculated by indices of absolute reliability were considerably higher in LD children versus TA children. The results of the current study could have implications for detecting real training-related changes in the ear scores.