The Validity and Reliability of Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) in Turkish Community

Abstract

Scientific Background: Alzheimer's Disease Assesment Scale (ADAS) is a scale specifically designed for assesment of the cognitive and noncognitive dysfunctions seen in Alzheimer's disease. The cognitive subscale of the instrument (ADAS-Cog) is the most widely used test in clinical trials dealing with Alzheimer's disease. The validity and reliability of the test has been investıgated for many communities. Objectives: The aim of the present study was to investigate the validity and reliability of the Turkish version of ADAS-Cog and to introduce the test for ptactical use in clinical trials of Alzheimer's disease in Turkey. Material and Methods: 26 patients with Alzheimer's Disease (AD), fullfilling DSM-IV criteria of dementia and NINCDS-ADRDA criteria of probable AD, who were in 3-6 stage according to the Global Deterioration Scale (GDS) and 23 non-demented control subjects with similar age, gender and educational status were recruited for the study. Both groups were applied Turkish version of ADAS-Cog and Standardized Mini Men tal Status examination , reliability and validity of which has already been established for the diagnosis of dementia in Turkish population. lnterrater reliability, internal consistency, test-retest reliability; face validity, differential validity and concurrent validity were statistically analyzed. Results: Both SMMT and ADAS-Cog have significantly differentiated demented and non-demented patients (p:0,000). A significant correlation has been established between SMMT and ADAS-Cog scores in AD group (r:-0,795). ADAS-Cog was also highly significantly correlated with GDS (r:0,789). For group with AD, non-demented and whole cohort coefficients of internal consistency a: 0.902, 0.516, 0.922; interrater reliability r: 0.977, 0.953, 0.988 and test-retest reliability r: 0.841, 0.849, 0.941 were found respectively. Age, gender and years ofeducation showed no impact on ADAS-Cog scores in both individual groups and in sum.Conclusion: The Turkish version of ADAS-Cog has been found highly reliable and valid in differentiating demented patients from nondemented subjects.