P-tau/Aβ42 and Aβ42/40 ratios in CSF are equally predictive of amyloid PET status

Introduction: Measurement of amyloid beta (A beta 40 and A beta 42) and tau (phosphorylated tau [p-tau] and total tau [t-tau]) in cerebrospinal fluid (CSF) can be utilized to differentiate clinical and preclinical Alzheimer's disease dementia (AD) from other neurodegenerative processes. Methods: CSF biomarkers were measured in 150 participants from the Mayo Clinic Study of Aging and the Alzheimer's Disease Research Center. P-tau/A beta 42 (Roche Elecsys, Fujirebio LUMIPULSE) and A beta 42/40 (Fujirebio LUMIPULSE) ratios were compared to one another and to amyloid positron emission tomography (PET) classification. Results: Strong correlation was observed between LUMIPULSE p-tau/A beta 42 and A beta 42/40, as well as Elecsys and LUMIPULSE p-tau/A beta 42 and A beta 42/40 (Spearman's rho = -0.827, -0.858, and 0.960, respectively). Concordance between LUMIPULSE p-tau/A beta 42 and A beta 42/40 was 96% and between Elecsys p-tau/A beta 42 and both LUMIPULSE ratios was 97%. All ratios had > 94% overall, positive, and negative percent agreement with amyloid PET classification. Discussion: These data suggest that p-tau/A beta 42 and A beta 42/40 ratios provide similar clinical information in the assessment of amyloid pathology.