Prognosis of BK polyomavirus nephropathy: 10-year analysis of 133 renal transplant recipients at a single center

Background: BK virus-associated nephropathy (BKVN) is an important cause of chronic allograft dysfunction. The objective of our study was to evaluate the prognosis of BKVN. Methods: We retrospectively reviewed the data of 133 renal transplant recipients with BKVN treated at the First Affiliated Hospital of Sun Yat-Sen University between July 2007 and July 2017. BK viral loads, graft function, and pathologic indexes were compared between initial diagnosis and last follow-up. Results: After a mean follow-up period of 14.4 (range, 0.3–109.6) months after diagnosis of BKVN, BK viruria, and BK viremia become negative in 19.5% and 90.2% of patients, respectively. The mean estimated glomerular filtration rate (eGFR) at last follow- up was lower than at diagnosis of BKVN (18.3 ± 9.2 vs. 32.8 ± 20.6 mL·min^-1·1.73 m^-2, t= 7.426, P < 0.001). Eight (6.0%) patients developed acute rejection after reducing immunosuppression. At last follow-up, the eGFR was significantly lower in patients with subsequent rejection than those without (21.6 ± 9.8 vs. 33.5 ± 20.9 mL·min^-1·1.73 m^-2, t= 3.034, P= 0.011). In 65 repeat biopsies, SV40-T antigen staining remained positive in 40 patients and became negative in the other 20 patients. The eGFR (42.6 ± 14.3 vs. 26.5 ± 12.3 mL·min^-1·1.73 m^-2), urine viral loads (median, 1.3 × 105vs. 1.4 × 107 copies/mL), and plasma viral load (median, 0 vs. 0 copies/mL) were all significantly lower in patients with negative SV40-T antigen staining than those with persistent BK involvement (all, P < 0.05). Five (3.8%) recipients lost their graft at diagnosis of BKVN, and 13 (9.8%) lost their graft during the follow-up period. The 1-, 3-, and 5-year graft survival rates after diagnosis of BKVN were 99.2%, 90.7%, and 85.7%, respectively. Higher pathologic stage correlated with lower allograft survival rate (χ^2= 6.341, P= 0.042). Conclusion: Secondary rejection and persistent histologic infection in BKVN lead to poor prognosis.

Combined detection of urine specific gravity and BK viruria on prediction of BK polyomavirus nephropathy in kidney transplant recipients

Background:BK polyomavirus(BKPyV)-associated nephropathy(BKPyVAN)is an important cause of dysfunction and failure of renal transplants.This study aimed to assess the diagnostic performance of morning urine specific gravity(MUSG)in diagnosing BKPyVAN in kidney transplant recipients.Methods:A total of 87 patients,including 27 with BKPyVAN,22 with isolated BKPyV viruria,18 with T cell-mediated rejection(TCMR),and 20 with stable graft function,were enrolled in the First Affiliated Hospital of Sun Yat-Sen University from March 2015 to February 2017.MUSG at biopsy and during a follow-up period of 24 months after biopsy was collected and analyzed.Receiver operating characteristic(ROC)curve analysis was used to determine the ability of MUSG to discriminate BKPyVAN.Results:At biopsy,the MUSG of BKPyVAN group(1.008±0.003)was significantly lower than that of isolated BK viruria group(1.013±0.004,P<0.001),TCMR group(1.011±0.003,P=0.027),and control group(1.014±0.006,P<0.001).There was no significant difference in MUSG among the isolated BK viruria group,TCMR group,and control group(P=0.253).In BKPyVAN group,the timing and trend of MUSG elevate were consistent with the timing and trend of the decline of viral load in urine and plasma,reaching a statistical difference at 3 months after treatment(1.012±0.003,P<0.001)compared with values at diagnosis.ROC analysis indicated that the optimal cut-off value of MUSG for diagnosis of BKPyVAN was 1.009,with an area under the ROC curve(AUC)of 0.803(95%confidence interval[CI]:0.721–0.937).For differentiating BKPyVAN and TCMR,the optimal MUSG cut-off value was 1.010,with an AUC of 0.811(95%CI:0.687–0.934).Conclusion:Combined detection of MUSG and BKPyV viruria is valuable for predicting BKPyVAN and distinguishing BKPyVAN from TCMR in renal transplant recipients.