TREM2 has been reported to be associated with Alzheimer's disease (AD). Here, we 
evaluated TREM2 mRNA and protein expressions in peripheral blood from AD 
patients and healthy controls. Higher levels of TREM2 mRNA (p = 0.002) and 
protein (p < 0.001) were identified in AD patients. We observed a significant 
correlation between TREM2 expressions and MMSE score (mRNA: r = -0.482, protein: 
r = -0.582; p < 0.01). According to ROC curve analysis, the diagnostic accuracy 
for TREM2 protein levels on monocytes was 70%, with the sensitivity and 
specificity 68% and 72%, respectively. Our results indicate that TREM2 might 
serve as a novel noninvasive biomarker for AD diagnosis.