Detection of Alzheimer's disease amyloid beta 1-42, p-tau, and t-tau assays

Introduction We aimed to provide cut points for the automated Elecsys Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers. Methods Cut points for Elecsys amyloid beta 42 (A beta 42), total tau (t-tau), hyperphosphorylated tau (p-tau), and t-tau/A beta 42 and p-tau/A beta 42 ratios were evaluated in Mayo Clinic Study of Aging (n = 804) and Mayo Clinic Alzheimer's Disease Research Center (n = 70) participants. Results The t-tau/A beta 42 and p-tau/A beta 42 ratios had a higher percent agreement with normal/abnormal amyloid positron emission tomography (PET) than the individual CSF markers. Reciever Operating Characteristic (ROC)-based cut points were 0.26 (0.24-0.27) for t-tau/A beta 42 and 0.023 (0.020-0.025) for p-tau/A beta 42. Ratio cut points derived from other cohorts performed as well in our cohort as our own did. Individual biomarkers had worse diagnostic properties and more variable results in terms of positive and negative percent agreement (PPA and NPA). Conclusion CSF t-tau/A beta 42 and p-tau/A beta 42 ratios are very robust indicators of AD. For individual biomarkers, the intended use should determine which cut point is chosen.

Automated summary

CSF t-tau/A beta 42 and p-tau/A beta 42 ratios are robust indicators of AD with higher agreement with amyloid PET scans. Individual biomarkers have worse diagnostic properties and more variable results in terms of positive and negative percent agreement.