CDK5 and Alzheimer disease: From ROC analysis and Youden’s index, the area under curve (AUC) for Cdk5 was 0.90 for differentiating AD vs. GC (24.97 ng/μL cutoff, 89.66% sensitivity, and 80.65% specificity), 0.67 AUC for differentiating AD vs. MCI (26.75 ng/μL cutoff, 66.07% sensitivity, and 56.45% specificity), and 0.85 AUC for differentiating MCI vs. GC (24.26 ng/μL cutoff, 79.31% sensitivity, and 71.31% specificity).