Development of a High-Sensitivity Method for the Measurement of Human Nasal Aβ(42), Tau, and Phosphorylated Tau

Cost-effective and feasible methods for early diagnosis of Alzheimer’s disease (AD) are needed. We present two methods to measure AD-related biomarkers simultaneously from one nasal smear for the purpose of diagnosing AD. Japanese men and women aged 63–85 years old were recruited in 2015–2016 for this case–control study. A total of 25 AD cases and 25 controls (22 men and 28 women) participated in this research. Nasal smears were collected from the common nasal meatus, inferior concha, middle nasal meatus, and olfactory cleft, and the proteins in the samples were analyzed by two methods, which we named PGD (Pre-treatment with guanidine- n-Dodecyl-beta-D-maltoside solution) method 1 (PGD-I) and 2 (PGD-II). The PGD-I method measured total tau and amyloid-β (Aβ)(42), but no differences in median levels of total tau and Aβ(42) between AD cases and controls were found in any of the nasal locations. The PGD-II method measured Aβ(42), total tau, and phosphorylated tau, but levels of Aβ(40) in all nasal locations of both groups were near zero. Median levels of phosphorylated tau to total tau (p-tau/t-tau) ratios in the middle nasal meatus and in the olfactory cleft were significantly higher in AD cases than in controls, and could significantly predict AD. To assess diagnostic reliability, areas under the ROC curve were 0.74 (95% CL = 0.52–0.95, p = 0.030) for the middle nasal meatus and 0.72 (95% CL = 0.52–0.92, p = 0.029) for the olfactory cleft. Thus, PGD-I and PGD-II can detect AD-related biomarkers in nasal smears and PGD-II may be a useful tool for diagnosing AD.