The Evaluation of Serum Total Tau, NFL, Neurogranin, YKL-40, and FABP-3 as Screening Biomarkers for Alzheimer’s Disease

Objective: Alzheimer’s disease (AD) is a neurodegenerative disorder that causes dementia and accounts for 50-75% of all cases. Since cerebrospinal fluid sampling (CSF) is an invasive procedure, there is a need for non- or less invasive alternatives to identify new biomarkers that reflect the underlying AD pathology.Materials and Methods: Blood samples were obtained from 86 AD patients (33 mild, 29 moderate, and 24 severe AD) and 30 controls. Serum total tau, neurofilament light polypeptide (NFL), neurogranin, chitinase-3-like protein 1 (YKL-40), and fatty acid-binding protein 3 (FABP-3) were measured using enzymelinked immunosorbent assay (ELISA).Results: Serum total tau and NFL levels were higher in AD patients compared to controls, whereas neurogranin, YKL-40, and FABP-3 levels remained unchanged. In the receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity for total tau alone (cut-off point: 71.5 pg/mL) were 79.1% and 76.7% (Area under the curve (AUC): 0.865; p<0.001), while the sensitivity and specificity for NFL alone (cut-off point: 1.835 pg/mL) were 66.3% and 66.7% (AUC: 0.693; p=0.002). When total tau and NFL were concomitantly evaluated, the AUC was 0.848 (p<0.001).Conclusion: Alongside the established core AD biomarkers, serum total tau and NFL are promising biomarkers for AD, reflecting additional pathological changes during the disease.