BACKGROUND Diagnosis of prodromal Alzheimer’s disease (AD) and AD dementia in people with Down’s Syndrome (DS) is a major challenge. The Cambridge Examination for Mental Disorders of Older People with DS and Others with Intellectual Disabilities (CAMDEX-DS) has been validated for diagnosing prodromal AD and AD dementia but the diagnostic process lacks guidance.

AIMS To derive CAMDEX-DS informant interview threshold scores to enable accurate diagnosis of prodromal AD and AD dementia in adults with DS.

METHOD Psychiatrist’s classified participants with DS into no dementia, prodromal AD and AD dementia groups. Receiver operating characteristic (ROC) analyses assessed the diagnostic accuracy of CAMDEX-DS informant interview derived scores. Spearman partial correlations investigated associations between CAMDEX-DS scores, regional Aβ binding (positron emission tomography) and regional cortical thickness (magnetic resonance imaging).

RESULTS Diagnostic performance of CAMDEX-DS Total scores were high for AD dementia (area under the curve (AUC): 0.998; 95% CI 0.953-0.999) and prodromal AD (AUC: 0.954; 95% CI 0.887-0.982) when compared to healthy DS adults. When compared to those with mental health conditions but no AD, CAMDEX-DS Section B scores, denoting memory and orientation ability, accurately diagnosed AD dementia (AUC: 0.958; 95% CI 0.892-0.984), but were unable to diagnose prodromal AD. CAMDEX-DS Total scores exhibited moderate correlations with cortical Aβ (r ∼ 0.4 to 0.6, P ≤ 0.05) and thickness (r ∼ -0.4 to -0.44, P ≤ 0.05) in specific regions.

CONCLUSIONS CAMDEX-DS Total score accurately diagnoses AD dementia and prodromal AD in healthy DS adults