Elevated expression of specific microRNAs (miRNA) in peripheral blood-derived 
mononuclear cells (PBMC), particularly miR-146a and miR-155, is associated with 
rheumatoid arthritis (RA). Whole blood has not been explored as a potential 
clinical material for monitoring the expression of miRNAs in RA. We sought to 
determine whether miRNA levels detected in whole blood samples correlated with 
those detected in simultaneously isolated peripheral blood-derived mononuclear 
cells (PBMC) from the same individuals, thus establishing the feasibility of 
using whole blood as a viable clinical material for monitoring miRNA expression 
in RA and other disorders. We demonstrated a highly significant linear 
correlation between miR-146a and miR-155 expression in PBMC and whole blood, 
from both healthy individuals and RA patients. Whole blood samples accurately 
reflect miRNA levels in PBMC and would be useful in monitoring the expression of 
miRNAs as biomarkers. The detection of miRNA levels in samples that are readily 
obtained in routine clinical practice, such as whole blood, enhances their 
potential utility in detecting changes in the immunological mechanisms 
underlying autoimmune diseases such as RA.