Diagnostic value of three urine miRNAs composite score in BK virus nephropathy

Noninvasive detection of BK virus, for early detection of BK polyomavirus-associated nephropathy post-renal transplantation, is currently an active subject of investigation. In this study, we developed and validated a novel risk score diagnostic assay (PymiR Score) based on measurements of three urine miRNAs, including BKV-related miRNA (bkv-miR-B1-5p), polyomavirus-related miRNA (bkv-miR-B1-3p) and renal tubular injury-related miRNA (miR-21-5p), by quantitative polymerase chain reaction. The limit of detection of the three miRNAs was 2 × 10³ copies/mL, while the intra- and inter-assay coefficients of variation were in the ranges of 2.13 %-3.59 % and 2.30 %-3.35 %, respectively. In the training set, we identified that at a PymiR Score of 71.78, the maximum sensitivity and specificity for the detection of BKVAN were 76.9 % and 100 % respectively, with the receiver-operator characteristic (ROC) analysis showing an area under the curve of 0.8681. In the validation set, we observed a significant difference in the PymiR Score between BKV infection and biopsy-proven BKVAN (P ＜ 0.05), with the ROC analysis showing a sensitivity of 72.73 %, specificity of 100 %, and an AUC of 0.8571. Compared with the area under the ROC curve of plasma BK virus DNA load (AUC = 0.7266), the PymiR Score exhibited higher discrimination capacity (P＜0.05) between BKV infection and biopsy-proven BKVAN. Overall, this non-invasive approach offers a robust and convenient alternative for the diagnosis of BK polyomavirus-associated nephropathy.