Language comprehension assessment using the computer-based instrument for low motor language testing (C-BiLLT) in children with Angelman syndrome

Angelman syndrome (AS) is a rare genetic neurodevelopmental disorder with intellectual disability, limited to no speech development, epilepsy, motor deficits, and behavioral issues. Children with AS generally demonstrate better language comprehension than expressive language skills, but language comprehension is difficult to measure since commonly used tests rely on fine motor skills and/or require a certain level of intellectual functioning. The Computer-Based instrument for Low motor Language Testing (C-BiLLT) was developed to assess language comprehension in non-speaking children with motor impairments. This study assessed the feasibility, construct validity and sensitivity of the C-BiLLT in a clinical cohort of 65 children with AS (2 to 19 years old). All participants successfully finished the test, without floor or ceiling effects. The C-BiLLT showed good construct validity, reflected by a significant correlation with the Bayley language comprehension subscale and with related constructs (expressive language measured by the Communication Matrix and the Bayley cognition subscale). C-BiLLT scores were associated with age. Finally, the C-BiLLT was sensitive to differentiate between AS genotypes. In conclusion, we demonstrate that the C-BiLLT is a feasible, valid and sensitive measurement instrument for language comprehension in children with AS. We recommend using the C-BiLLT in clinical practice and in scientific research.