Abstract
Objective: Biomarker-based early detection of Alzheimer’s disease (AD) and mild cognitive impairment (MCI) is important for early intervention and prevention of dementia. We previously developed an ‘MCI screening blood test’ involving the testing of triple markers (apolipoprotein A1, transthyretin, and complement protein C3) for the evaluation of cognitive impairment in older adults. In this study, we combined the MCI screening blood test with testing of plasma Aβ40 and Aβ42 levels to evaluate the clinical potential of these five markers in the diagnosis of MCI and AD.
Methods: Through an immunoassay, we measured plasma Aβ40 and Aβ42 levels and triple marker levels in samples of 178 AD, 145 MCI, and 40 cognitively healthy elderly (NDC) patients.
Results: Plasma levels of the triple markers were lower in MCI and AD than in NDC patients. Receiver operating characteristic curve analysis revealed that the composite of triple markers had relative area under the curve (AUC) values of 0.81 and 0.74 in AD vs. NDC and MCI vs. NDC, respectively. The Aβ40/42 ratio had an AUC of 0.71 (AD vs. NDC) and 0.62 (MCI vs. NDC). Furthermore, addition of the triple markers to the Aβ40/42 ratio resulted in AUC values of 0.85 (sensitivity 80%, specificity 85%) in AD vs. NDC and 0.81 (sensitivity 77%, specificity 73%) in MCI vs. NDC.
Conclusion: Blood tests determining these triple markers’ levels and the Aβ40/42 ratio may be useful during routine health checks to evaluate the progression of cognitive impairment in older adults.
