For example, in Alzheimer’s disease (AD), protein-based biomarkers such as phosphorylated tau (p-Tau) and the Aβ42/Aβ40 ratio are typically measured in cerebrospinal fluid (CSF) using sensitive immunoassays, with detection limits in the low pg/mL range [31]. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.