Assessing language comprehension in motor impaired children needing AAC: validity and reliability of the Norwegian version of the receptive language test C-BiLLT.

Children with severe motor impairments who need augmentative and alternative communication (AAC) comprise a heterogeneous group with wide variability in cognitive functioning. Assessment of language comprehension will help find the best possible communication solution for each child, but there is a lack of appropriate instruments. This study investigates the reliability and validity of the Norwegian version of the spoken language comprehension test C-BiLLT (computer-based instrument for low motor language testing) - the C-BiLLT-Nor - and whether response modality influences test results. The participants were 238 children with typical development aged 1;2 to 7;10 (years/months) who were assessed with the C-BiLLT-Nor and tests of language comprehension and non-verbal reasoning. There was excellent internal consistency and good test-retest reliability. Tests of language comprehension and non-verbal reasoning correlated significantly with the C-BiLLT-Nor, indicating good construct validity. Factor analysis yielded a two-factor solution, suggesting it as a measure of receptive vocabulary, grammar, and overall language comprehension. No difference in results could be related to response mode, implying that gaze pointing is a viable option for children who cannot point with a finger. The C-BiLLT-Nor, with norms from 1;6-7;6 is a reliable measure of language comprehension.