Establishing diagnostic thresholds for Alzheimer's disease in adults with Down syndrome: the Cambridge Examination for Mental Disorders of Older People with Down's Syndrome and Others with Intellectual Disabilities (CAMDEX-DS)

Jessica A Beresford-Webb; Elijah Mak; Monika Grigorova; Samuel J Daffern; Anthony J Holland; Shahid H Zaman

doi:10.1192/bjo.2021.36

Establishing diagnostic thresholds for Alzheimer's disease in adults with Down syndrome: the Cambridge Examination for Mental Disorders of Older People with Down's Syndrome and Others with Intellectual Disabilities (CAMDEX-DS)

BJPsych Open. 2021 Apr 13;7(3):e79. doi: 10.1192/bjo.2021.36.

Authors

Jessica A Beresford-Webb¹, Elijah Mak¹, Monika Grigorova¹, Samuel J Daffern², Anthony J Holland¹, Shahid H Zaman¹

Affiliations

¹ Department of Psychiatry, University of Cambridge, UK.
² Department of Genetics, University of Cambridge, UK.

Abstract

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

Aims: To derive CAMDEX-DS informant interview threshold scores to enable accurate diagnosis of prodromal Alzheimer's disease and Alzheimer's disease dementia in adults with Down syndrome.

Method: Psychiatrists classified participants with Down syndrome into no dementia, prodromal Alzheimer's disease and Alzheimer's disease dementia groups. Receiver operating characteristic 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 Alzheimer's disease dementia (area under the curve (AUC), 0.998; 95% CI 0.953-0.999) and prodromal Alzheimer's disease (AUC = 0.954; 95% CI 0.887-0.982) when compared with healthy adults with Down syndrome. When compared with those with mental health conditions but no Alzheimer's disease, CAMDEX-DS Section B scores, denoting memory and orientation ability, accurately diagnosed Alzheimer's disease dementia (AUC = 0.958; 95% CI 0.892-0.984), but were unable to diagnose prodromal Alzheimer's disease. 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 Alzheimer's disease dementia and prodromal Alzheimer's disease in healthy adults with Down syndrome.

Keywords: Alzheimer's disease; CAMDEX-DS; Dementia; imaging; intellectual disability.

Abstract

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