Background Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterised by autoantibody production, complement activation and deposition of immune complexes in tissues and organs. Its pathogenesis is still unknown but recent studies reveal the biological and clinical relevance of altered microRNAs (miRNAs) expression in SLE – in serum, peripheral blood (PB) monocytes, T- and B-cells. The aim of our study was to evaluate the diagnostic and prognostic value of PB expression levels of miR-146a and miR-155 in SLE patients.

Materials and methods 40SLE patients according to the 1981 ACR criteria were included in the study. miR-155 and -146a expression levels in whole PB samples were determined by PCR (SYBR Green technology) and 2^-∆∆Ct method was used for analysis. 32 healthy donors were usedas controls. SPSS v20 was used for ROC curve and Spearman correlation analysis.

Results ROC curve analysis showed that the expression levels of miR-146a (AUC-0.711, p = 0.002) in PB better discriminate SLE patients from HCs with 82.5% sensitivity and 56.2 % specificity in comparison to miR-155 (AUC-0.691, p = 0.005, 77.5% sensitivity and 50.0% specificity). Diagnostic accuracy did not improve much when combination of the studied miRNAs was used in multimarker ROC curve analysis (AUC-0.716, p = 0.002, 82.5% sensitivity and 56.2% specificity). miR-146a and miR-155 showed statistically significant correlation with diagnosis (r_s = 0.363 and 0.330, respectively) and age (r_s = 0.239 and 0.366, respectively). miR-155 showed also correlation with the presence of secondary Raynaud syndrome with Spearman correlation coefficient 0.250.

Conclusions Our data showed that the expression levels of miR-146a and miR-155 in PB could be used as diagnostic biomarkers for SLE in Bulgarian patients but larger study is needed to confirm these results.

Acknowledgement The study was supported by Grant 53/2014 funded by Medical University – Sofia, Bulgaria.