Abstract
Background: Identification of risk factors for BK virus (BKV) replication and BKV -associated nephropathy(BKVAN) may improve renal transplant outcome. We investigated risk factors for different type of BKV infection and BKVAN through observation of clinical course of BKV infection. Methods: Between 2006 and 2013, renal transplant graft biopsies combined with BKV screening were performed in 491 patients. A total of 39 (7.9%) cases of BKVAN were diagnosed by simian virus 40 (SV40) staining and quantitative PCR assay for BKV DNA load in urine and plasma and quantitative assay of urine cytology by light microscopy or electron microscopy.39 patients with BKVAN and 30 patients with BKV infection were treated with immunosuppression reduction and were monitored for BKV every 1-4 weeks. Potential variables were compared and analyzed by Logistic regression model multivariate analysis to assess and rank the BKV infection related factors. Results: Multivariate analysis showed that Tac, high Tac trough level(>6.5ng/ml), and severe pneumonia early after transplant were risk factors for BK decoy cells, BK viruria, viremia, and BKVAN respectively. During 7(1-84) months follow-up after immunosuppression reduction, the rates of BK viruria clearance were higher in non-BKVAN group(93.3%) than that in BKVAN group(32.4%, p<0.001). BKVAN patients had longer BK viruria(16.4 vs 2.4 months, p=0.002) and viremia(3.9 vs 0.5 months, p=0.001) clearance time, compared with non-BKVAN patients. Defining BK viruria clearance as an event, BKVAN compared with non- BKVAN was associated with slow viral reduction (P<0.001).The renal function in the patients with non-BKVAN remained stable at the end of follow-up. Conclusions: Tac and high Tac trough level are independent risk factors for BKV infection and BKVAN. BKVAN is inclined to the patient with longer BKV clearance time despite of immunosuppression reduction.Figure: No Caption available.
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