Validity and reliability of the Intelligibility in Context Scale: European Portuguese version

The purpose of the study was to evaluate the validity, reliability, sensitivity and specificity of the European-Portuguese version of the Intelligibility in Context Scale (ICS-EP). Seventy-six children (age: M = 60.6, SD = 8.1 months), 25 having a parent or teacher concern about how they talked and 51 with no concern, were assessed with the phonetic-phonological test (TFF-ALPE) to calculate the following severity measures: percentage of phonemes correct (PPC), percentage of consonants correct (PCC), and percentage of vowels correct (PVC). Parents also filled out a questionnaire about their child's development (e.g. concern about how the child talks). The ICS was then completed by parents to estimate their children's intelligibility with different communicative partners. The results showed that item-level scores were different according to communicative partners. The mean ICS score for the whole sample was 4.5 (SD = 0.6), showing that children were "usually" to "always" intelligible. The ICS had excellent internal consistency (α = 0.96). Children with parental concern about their speech presented significantly lower mean scores (M = 3.91, SD = 0.59) than children without parental concerns (M = 4.78, SD = 0.36). There was a positive correlation between the ICS scores and PPC (r = .655), PCC (r = .654), and PVC (r = .588). A simple linear model was also obtained between the ICS mean score and the severity measures analyzed. High values were obtained for sensitivity (0.80) and specificity (0.84), using a cut-off point of 4.36. We conclude that the ICS-EP has good psychometric properties, suggesting it to be a valid tool for estimating children's intelligibility when talking with different communicative partners. Therefore, this version of the ICS can be used as a screening measure for children's speech intelligibility.