The researchers conducted this study to compare the reliability, validity, and measurement properties of the Supports Intensity Scale–Children’s Version (SIS-C) in 2124 children with autism and intellectual disability and 1861 children with an intellectual disability only.

The results obtained after the careful analysis suggest that SIS-C is a valid and reliable tool in both populations with autism and intellectual disability. Furthermore, the results of multi-group confirmatory factor analyses indicated that measurement invariance can be established across children with autism and intellectual disability but that latent differences are present. Specifically, children with autism and intellectual disability tend to have higher intensities of support needs in social activities across age cohorts (5- to 6-, 7- to 8-, 9- to 10-, 11- to 12-, 13- to 14, and 15- to 16-year-olds). Children with an intellectual disability only tended to have stronger correlations among support need domains measured on the SIS-C.

The study provided implications for applying the SIS-C to assessment and support planning through the obtained findings and results that shall be used in clinical settings.