Development and validation of the Ascertain Dementia 8 (AD8) Thai version

The Ascertain Dementia 8 (AD8) is a brief informant-based questionnaire which reliably distinguishes patients with neurocognitive disorder (NCD) and normal cognition. Our objective was to translate the AD8 into Thai and test its validity as a potentially useful measure to detect patients with the mild stage of major NCD due to Alzheimer disease (major NCD-AD).

Evaluations of 144 informant-patient dyads were made. Participants were patients who attended the memory clinic at Ramathibodi Hospital and non-patient volunteers. The AD8-Thai version was administered separately from doctor's interviews and neuropsychological assessments. Diagnostic workups included a complete medical history, physical and neurological examinations, neuropsychological testing, the Clinical Dementia Rating Scale-Sum of Boxes (CDR-SOB), Montreal Cognitive Assessment (MoCA), blood tests and brain imaging, preferably with magnetic resonance imaging. All researchers were blinded to the AD8 results.

An AD8 score ≥3 had a sensitivity of 95.5%, a specificity of 89.5%, a positive predictive value of 84%, and a negative predictive value of 97.1% for screening major NCD-AD and those with normal cognition. A subgroup analysis with participants aged ≥65 years and with ≥12 years of education revealed comparable ability to the whole group. AD8 scores had a moderate negative relationship with MoCA scores (r = -0.470) and a strong positive relationship with CDR-SOB scores (r = 0.547). The performance of AD8 scores in differentiating mild NCD from normal cognition was not as good as for major NCD-AD.

AD8-Thai version is an acceptable screening tool for major NCD-AD. For patients aged 65 years or older, with at least 12 years of education, and with cognitive complaints in memory clinic, an AD8-Thai score of 3 or more would be sufficient to work on major NCD diagnosis. The performance of the AD8-Thai in mild NCD needs further investigation.