Objective Speech-language pathologists (SPLs) collect spontaneous language samples as a key component of clinical assessment protocols through contexts such as free play, picture description, and story retelling. Another context to collect language samples is through interviews. This study aimed to validate and examine the psychometric properties of Evans and Craig’s interview protocol for Persian-speaking preschool children with and without Language impairment
Materials & Methods Using systematic random sampling, language samples were selected from 207 Persian-speaking preschool children in Semnan, Iran (51 children with language impairment, 156 children without language impairment) and analyzed. The children were assessed using the Persian version of the test of language development–3 (TOLD-P3) and Evans and Craig’s 15-minute interview protocol. Cross-cultural adaptation was conducted according to Beaton et al.’s guidelines, followed by assessment of criterion validity, diagnostic accuracy, and responsiveness to change. Linguistic indices (mean length of utterance [MLU], number of conjunctions, ratio of complex to simple sentences, and type–token ratio [TTR]) and the overall language ability (OLA) score derived from the TOLD-P3 were calculated. All scores were entered into SPSS software, version 24. The scores of the two groups were compared using appropriate statistical tests. The significance level was set at 0.05.
Results The OLA score was 102.25 in typically developing children and 75 in children with language impairment. The mean MLU (6.11 vs 5.26; P=0.034) and number of conjunctions (13.37 vs 7.53; P=0.001) were significantly different between the two groups, but the ratio of complex to simple sentences (25.71 vs 25.87; P=0.63) and TTR  (0.44 vs 0.46; P=0.30) were not significantly different. Except for TTR, the other three indices showed significant correlations with OLA score (P<0.05). Regarding responsiveness, TTR was the only index that revealed significant changes at the six-month follow-up (P=0.004). The cut-off points were determined as follows: For MLU, <4.5; for number of conjunctions, <7; for ratio of complex to simple sentences, < 14%; and for TTR, 0.45–0.65, all of which may indicate language impairment in children aged 5–6.
Conclusion The Persian version of Evans & Craig’s interview protocol can be used in Persian-speaking children aged 5–6. SPLs can use this valid and practical tool to screen for and identify language impairments in preschoolers. The interview protocol has acceptable accuracy in distinguishing syntactic and semantic differences between children with and without language impairment.