MMP9 and Alzheimer disease: When distinguishing between the MCI group and the AD group, the six biomarkers, in the order of the highest to lowest AUC values, were MMP9 (AUC = 0.8680), UBR5 (AUC = 0.8592), APOE (AUC = 0.8496), STAT5B (AUC = 0.8272), S100A8 (AUC = 0.7856) and PLA2G7 (AUC = 0.7800) (Figure 6(i)).