Plasma Phospho-tau181 In Presymptomatic And Symptomatic Familial Alzheimer’s Disease: A Longitudinal Cohort Study
O’Connor A, Karikari TK, Poole T, Ashton NJ, Lantero Rodriguez J, Khatun A, Swift I, Heslegrave AJ, Abel E, Chung E, Weston PSJ, Pavisic IM, Ryan NS, Barker S, Rossor MN, Polke JM, Frost C, Mead S, Blennow K, Zetterberg H and Fox NC.
Mol Psychiatry (2020).
Blood biomarkers have great potential to advance clinical care and accelerate trials in Alzheimer’s disease (AD). Plasma phospho-tau181 (p-tau181) is a promising blood biomarker however, it is unknown if levels increase in presymptomatic AD. Therefore, we investigated the timing of p-tau181 changes using 153 blood samples from 70 individuals in a longitudinal study of familial AD (FAD). Plasma p-tau181 was measured, using an in-house single molecule array assay. We compared p-tau181 between symptomatic carriers, presymptomatic carriers, and non-carriers, adjusting for age and sex. We examined the relationship between p-tau181 and neurofilament light and estimated years to/from symptom onset (EYO), as well as years to/from actual onset in a symptomatic subgroup. In addition, we studied associations between p-tau181 and clinical severity, as well testing for differences between genetic subgroups. Twenty-four were presymptomatic carriers (mean baseline EYO −9.6 years) while 27 were non-carriers. Compared with non-carriers, plasma p-tau181 concentration was higher in both symptomatic (p < 0.001) and presymptomatic mutation carriers (p < 0.001). Plasma p-tau181 showed considerable intra-individual variability but individual values discriminated symptomatic (AUC 0.93 [95% CI 0.85–0.98]) and presymptomatic (EYO ≥ −7 years) (AUC 0.86 [95% CI 0.72–0.94]) carriers from non-carriers of the same age and sex. From a fitted model there was evidence (p = 0.050) that p-tau181 concentrations were higher in mutation carriers than non-carriers from 16 years prior to estimated symptom onset. Our finding that plasma p-tau181 concentration is increased in symptomatic and presymptomatic FAD suggests potential utility as an easily accessible biomarker of AD pathology.