Intelligibility in Context Scale: Growth Curves for Typically Developing English-Speaking Children Between Ages 2;6 and 9;11

PURPOSE

The aim of this study was to quantify the clinical utility of the Intelligibility in Context Scale (ICS) English version by characterizing the growth patterns of the ICS composite scores and seven ICS individual item scores of typically developing American English-speaking children.

METHOD

Parents of 545 typically developing children aged 2;6-9;11 (years;months) completed the ICS. Using a proportional odds model, we regressed ICS composite scores on age and computed for model-estimated mean and lower quantile ICS composite scores. Logistic regression and proportional odds modeling were utilized to quantify the relationship of individual ICS items and age.

RESULTS

ICS composite scores of typically developing children changed with age, but change was small and incremental, with scores compressed between 3 and 5 across the range of ages. An average child (i.e., on the 50th percentile) is expected to have an ICS composite score of 4 beginning at 3;0 and an ICS composite score of 5 by 6;6. On average, parents gave different intelligibility ratings based on communicative partners, and the rating differences between communicative partners decreased with age.

CONCLUSIONS

Given that ICS scores increase with age, the expected score for average children also increases. A child's age is a main factor for interpreting ICS scores.

Utility of the Intelligibility in Context Scale for Predicting Speech Intelligibility of Children with Cerebral Palsy

The Intelligibility in Context Scale (ICS) is a widely used, efficient tool for describing a child's speech intelligibility. Few studies have explored the relationship between ICS scores and transcription intelligibility scores, which are the gold standard for clinical measurement. This study examined how well ICS composite scores predicted transcription intelligibility scores among children with cerebral palsy (CP), how well individual questions from the ICS differentially predicted transcription intelligibility scores, and how well the ICS composite scores differentiated between children with and without speech motor impairment. Parents of 48 children with CP, who were approximately 13 years of age, completed the ICS. Ninety-six adult naïve listeners provided orthographic transcriptions of children's speech. Transcription intelligibility scores were regressed on ICS composite scores and individual item scores. Dysarthria status was regressed on ICS composite scores. Results indicated that ICS composite scores were moderately strong predictors of transcription intelligibility scores. One individual ICS item differentially predicted transcription intelligibility scores, and dysarthria severity influenced how well ICS composite scores differentiated between children with and without speech motor impairment. Findings suggest that the ICS has potential clinical utility for children with CP, especially when used with other objective measures of speech intelligibility.

Parent rating of intelligibility: A discussion of the construct validity of the Intelligibility in Context Scale (ICS) and normative data of the Swedish version of the ICS

BACKGROUND

Intelligibility can be defined as the speakers' ability to convey a message to the listener and it is considered the key functional measure of speech. The Intelligibility in Context Scale (ICS) is a parent rating scale used to assess intelligibility in children.

AIMS

To describe normative and validation data on the ICS in Swedish and to investigate how these are related to age, gender and multilingualism.

METHODS & PROCEDURES

Two studies were included. Study 1 included ICS forms from 319 Swedish-speaking children (3:2-9:2 years:months). Study 2 included video recordings and ICS forms from 14 children with speech sound disorder (SSD) and two with typical speech. The video recordings were transcribed in the validation process, resulting in intelligibility reference scores to which ICS scores were correlated.

OUTCOMES & RESULTS

Study 1: The mean value of the ICS for the 319 children was 4.73. There were no differences in ICS score related to age or gender. The children in the multilingual group were significantly older than the monolingual group and had significantly lower ICS scores than the group of monolinguals. Study 2: There was a moderate correlation between the ICS score and the transcription-based intelligibility score, with the two children with typical speech excluded; however, this correlation was not significant.

CONCLUSIONS & IMPLICATIONS

We contribute mean scores and percentiles on the ICS for Swedish-speaking children. The finding that the ICS does not provide valid measures of intelligibility for the included children with SSD suggests that the instrument measures a different construct.

WHAT THIS PAPER ADDS

What is already known on the subject The ICS has been translated to numerous languages and validated against articulation measures in several previous studies. The validity of the Swedish version has been investigated against intelligibility based on transcription of single words. What this paper adds to existing knowledge The study provides normative values of the Swedish version of the ICS for children aged 3-9 years. This is the first study to use a gold standard measure of intelligibility in continuous speech to validate the ICS. The results show a somewhat dubious validity regarding ICS for the group of children with SSD included in the study. What are the potential or actual clinical implications of this work? The ICS's suitability as a measure of intelligibility is questionable; however, it might be of use for speech and language pathologists to give an overview of the parents' view of their child's ability to communicate, in order to make a decision on possible further assessment and intervention. The normative values of the Swedish version of the ICS could be of use in this decision process.