Objectives: To examine the utility of the 'Severe Impairment Battery' (SIB--Thames Valley Test Company) in assessing cognitive ability of adults with Down syndrome.
Design: A within-subject repeated measures design was used to determine test-retest reliability of the SIB and the Vineland Adaptive Behaviour Scales (Interview Edition--Survey Form, 1984) were used to establish SIB criterion validity.
Methods: Thirty-three adults with Down syndrome (from 152 known to an NHS Trust learning disability service) were selected on the basis of their or their carers' written consent. At the first administration of the SIB with the participant, a staff member completed a Vineland ABS. Thirty days later, the SIB was readministered to the participant.
Results: Test-retest reliability of the SIB was high as was criterion validity determined by correlating SIB and Vineland ABS scores. Floor effects were not encountered.
Conclusions: The SIB can successfully be used with adults with Down syndrome to assess cognitive functioning over a wide range of ability and may be useful, if used longitudinally, in assessing for deterioration in cognitive functioning associated with dementia. Methodological limitations are discussed.