Evaluation of plasma amyloid peptides Aβ1-40 and Aβ1-42 as diagnostic biomarker of alzheimer's disease, its association with different grades of clinical severity and 18f-fluorodeoxyglucose positron emission tomography Z score in the Indian population: A case-control study

Background: We estimated plasma amyloid-peptides levels (A beta(1-42) and A beta(1-40)) as diagnostic biomarker of Alzheimer's disease (AD) and evaluated its association with clinical severity and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) Z score of the different brain regions in the Indian population. Patients and Methods: A case-control study was conducted. Diagnostic and statistical manual-IV, Dubois, and NIA-AA criteria were used for the diagnosis of AD. The plasma A beta(1-42) and A beta(1-40) concentration and 18F-FDG PET Z score were estimated for different brain regions. Results: Forty-seven cognitive impairment patients (AD = 29, mild cognitive impairment = 18) and 33 age-matched controls were enrolled. Plasma A beta(1-42) level was significantly higher in the AD group compared to controls (P = 0.046) and a cut-off >5.7 ng/mL has a specificity of 96.9%, sensitivity of 27.6%, positive predictive value 88.9%, and negative predictive value 60.4% for differentiating AD patients from controls. Significant correlation was seen between A beta(1-40)/A beta(1-42) ratio and 18F-FDG PET Z score in the bilateral-parietal, temporal, frontal-association area, and posterior-cingulate areas. Conclusion: As a diagnostic biomarker of AD, plasma A beta(1-42) level showed good specificity but low sensitivity in the Indian population.