Our results suggest that while CSF 14-3-3β is less accurate than CSF p-tau and CSF t-tau in discriminating CN Aβ− from Alzheimer’s disease Aβ+ or MCI Aβ+ individuals, CSF 14-3-3β performs similarly to plasma p-tau and plasma NfL. Here, MAPT is linked to early-onset autosomal dominant Alzheimer disease.