MAPT and Alzheimer disease: In Study 2, a significant higher concentration of ubiquitin was identified in the AD group compared to the control group (p < 0.001), see Figure 1B. In the control group correlations were found between T‐tau and ubiquitin (ρ = 0.84, p < 0.001) and P‐tau181 and ubiquitin (ρ = 0.80, p < 0.001), but not between Aβ1–42 and ubiquitin; see Supporting Information Figure S12.