Cerebrospinal fluid biomarkers and proximity to diagnosis in preclinical familial Alzheimer's disease

Abstract

Background/aims: Biological markers of utility in tracking Alzheimer's disease (AD) during the presymptomatic prodromal phase are important for prevention studies. Changes in cerebrospinal fluid (CSF) levels of 42-amino-acid β-amyloid (Aβ(42)), total tau protein (t-tau) and phosphorylated tau at residue 181 (p-tau(181)) during this state are incompletely characterized.

Methods: We measured CSF markers in 13 carriers of familial AD (FAD) mutations that are fully penetrant for causing AD (PSEN1 and APP) and in 5 non-mutation-carrying family members.

Results: Even among the entirely presymptomatic mutation carriers (n = 9), Aβ(42) was diminished (388.7 vs. 618.4 pg/ml, p = 0.004), and t-tau (138.5 vs. 50.5 pg/ml, p = 0.002) and p-tau(181) (71.7 vs. 24.6 pg/ml, p = 0.003) were elevated. There was a negative correlation between Aβ(42) levels and age relative to the family-specific age of dementia diagnosis.

Conclusions: Our data are consistent with a decline in CSF Aβ(42) levels occurring at least 20 years prior to clinical dementia in FAD.

Fig. 1

Levels of CSF biomarkers with age adjusted for family-specific age at disease diagnosis. Lines represent quadratic fit lines with 95% confidence intervals. a Aβ₄₂ levels drop between 20 and 10 years prior to the expected age of diagnosable dementia. b t-tau. c p-tau₁₈₁.