Abstract
Introduction:BK virus (BKV) infection in renal transplant patients may cause kidney allograft dysfunction and graft loss. Accurate determination of BKV viral load is critical to prevent BKV-associated nephropathy (BKVAN) but the cut-off that best predicts BKVAN remains controversial.Objective:To evaluate the performance of a commercial and an in-house qPCR test for quantitative detection of BK virus in kidney transplant recipients.Methods:This was a prospective study with kidney transplant recipients from two large university hospitals in Brazil. Patients were screened for BKV infection every 3 months in the first year post-transplant with a commercial and an in-house real time polymerase chain reaction (qPCR) test. BKVAN was confirmed based on histopathology. The area under the curve for plasma qPCR was determined from receiver operating characteristic analysis.Results:A total of 200 patients were enrolled. Fifty-eight percent were male, 19.5% had diabetes mellitus, and 82% had the kidney transplanted from a deceased donor. BKV viremia was detected in 32.5% and BKVAN was diagnosed in 8 patients (4%). BKVAN was associated with viremia of 4.1 log copies/mL, using a commercial kit. The cut-off for the in-house assay was 6.1 log copies/mL. The linearity between the commercial kit and the in-house assay was R2=0.83.Conclusion: Our study shows that marked variability occurs in BKV viral load when different qPCR methodologies are used. The in-house qPCR assay proved clinically useful, a cheaper option in comparison to commercial qPCR kits. There is an urgent need to make BKV standards available to the international community.
Highlights
BK virus (BKV) infection in renal transplant patients may cause kidney allograft dysfunction and graft loss
Commercial tests based on quantitative real time polymerase chain reaction may be expensive for routine use in clinical practice and limited data is available on the performance of in-house qPCR BKV tests
Graft loss occurred in seven patients (3.5%) but BKV-associated nephropathy (BKVAN) was considered the cause for graft loss in only one patient (14.3%; overall incidence 0.5%)
Summary
BK virus (BKV) infection in renal transplant patients may cause kidney allograft dysfunction and graft loss. Patients were screened for BKV infection every 3 months in the first year post-transplant with a commercial and an in-house real time polymerase chain reaction (qPCR) test. Since no effective antiviral therapy is available to treat BKV infection, the best strategy relies on BKVAN prevention This may be achieved by frequent monitoring of BKV DNA load in urine and/or plasma samples, followed by a reduction of immunosuppressive therapy whenever significant viral replication is detected.[9] International societies have recommended 4 log of BKV DNA in the plasma as the cut-off value that best predicts BKVAN. Commercial tests based on quantitative real time polymerase chain reaction (qPCR) may be expensive for routine use in clinical practice and limited data is available on the performance of in-house qPCR BKV tests. It is critical for institutions to conduct clinical validation studies to certify that their methods are useful to accurately guide clinical decisions.[10,11,12,13,14,15,16,17]
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