Cognitive decline in Down syndrome: a validity/reliability study of the test for severe impairment.

The utility of the Test for Severe Impairment was studied with 60 older persons who had Down syndrome. Construct validity, test-retest reliability, and interrater reliability were established for the full study group and for subgroups based on degree of mental retardation and dementia status. There was no difference in scores by gender. There were some interesting findings for the group with moderate mental retardation and dementia and the group with severe mental retardation without dementia that may signal specific applications and limitations of the test for use with individuals who have Down syndrome. The internal consistency of the instrument was satisfactory. Results suggest that this test is a useful performance-based task for persons with Down syndrome.