LAUSR

OBJECTIVE Dementia frequently occurs in Down syndrome (DS) patients, and early intervention is important in its management. We have previously demonstrated a positive correlation of plasma β-amyloids Aβ42 level and negative correlations of Aβ40 and tau levels with dementia in DS. In this study, we examined more cases and constructed composite scores with both tau and amyloids to correlated with dementia in DS. METHODS Plasma Aβ42, Aβ40, and tau proteins were measured by an immunomagnetic reduction assay in DS patients. Data were randomly and repeatedly split into training and validating sets, and logistic regression was applied to calculate area under curves (AUCs) for each biomarker. RESULTS A total of 73 DS patients (among them 23 had neurodegeneration) and 77 controls were recruited. In DS patients without dementia, plasma Aβ40 and tau levels were highly elevated, but Aβ42 levels were lower than those of the healthy controls. DS patients with dementia, compared with DS patients with no dementia, had a large decline in Aβ40 and tau, but a rise in Aβ42. For biomarker scores correlating with dementia, Aβ40 revealed an AUC of 0.912; composite score Aβ40 × Tau revealed an AUC of 0.953; and a combined composite score of 0.1 Aβ40 × Tau + 0.9 Tau × Aβ40 / Aβ42 achieved the highest AUC of 0.965. INTERPRETATION Composite biomarker scores including both plasma tau and β-amyloids levels correlate with dementia in DS better than using individual biomarker scores. The pattern of tau decline and Aβ42 rise in DS patients with dementia are also different from previous findings in Alzheimer's disease.