Thus, the performance of our biomarker models was increased by which cathepsin D had a positive effect on AUC with good diagnostic accuracy based on AUC interpretation criteria (0.9–1.0 = excellent, 0.8–0.9 = very good, 0.7–0.8 = good, 0.6–0.7 = sufficient, 0.5–0.6 = bad, <0.5 = not useful) [36,37].Taken together, our findings suggest that plasma cathepsin D could be developed as a potential biomarker for the diagnosis of AD. Here, CTSD is linked to Alzheimer disease.