Objective  To detect the serum level of microRNA (miR)-155-5p in IgA nephropathy patients and examine its clinical significance.

Methods  The patients with IgA nephropathy followed up for 3 years were selected. Serum level of miR-155-5p was detected by real-time fluorescent quantitative polymerase chain reaction (PCR). Based upon declining rate of renal function (RF), they were assigned into two groups of RF progression (A, n=42) and relatively stable RF (B, n=63). Inter-group differences in clinical and laboratory parameters were compared. Logistic regression analysis was performed for identifying the risk factors for RF progression. Pearson’s or Spearman’s correlation analysis was performed for assessing the correlation between serum level of miR-155-5p and baseline estimated glomerular filtration rate (eGFR), urinary protein quantification, declining rate of RF and renal pathological data. Receiver operating characteristic (ROC) curve was plotted for evaluating the capability of miR-155-5p level for judging the progress of RF.

Results  As compared with group B, group A had a higher prevalence of hypertension (88.09% vs 19.05%), greater baseline urinary protein quantification (3.11±2.16)g/24 h vs (1.07±0.87)g/24 h, higher baseline blood creatinine (106.74±51.27)μmol/L vs (86.90±36.90)μmol/L and higher total kidney pathology T score (61 vs 13, P<0.05). Baseline eGFR (74.76±32.74)mL·min⁻¹·（1.73m²）⁻¹ vs (92.28±29.65)mL·min⁻¹·（1.73m²）⁻¹ and serum level of miR-155-5p (489.19±123.13)fmol/L vs (792.60±199.44)fmol/L were lower in group A (P<0.05). Variables with statistically significant inter-group differences were included for multifactorial Logistic regression analysis. It indicated that hypertension, urinary protein quantification, baseline eGFR, pathology score T and serum level of miR-155-5p were independent risk factors for RF progression of IgA nephropathy. Serum level of miR-155-5p was correlated negatively with declining rate of eGFR (r=−0.456, P<0.001). ROC curve for miR-155-5p in predicting RF progression had an area under the curve (AUC) of 0.918 with a sensitivity of 0.841, a specificity of 0.881 and an optimal cutoff value of 582.04 fmol/L.

Conclusion  Correlated negatively with RF progression, serum level of miR-155-5p may serve as a novel biomarker for predicting RF progression in IgA patients.