Advances in TransplantationKidney transplantationFeasibility of BK Virus Real-Time PCR Testing in Renal Graft Biopsies With Negative SV40 Staining

•Accepted technology (liquid BKV qPCR) is applied to a new medium (tissue).•qPCR from paraffin-embedded tissue is sensitive for ruling in/out BKV infection.•Implication is great in uncertain cases (negative SV40 IHC and positive serum/urine).

BackgroundBK virus (BKV)-associated nephropathy (BKVAN) is often associated with renal graft dysfunction. When renal transplant recipients present with high clinical suspicion for BKVAN (high serum and urine BKV titer with graft dysfunction) but their graft biopsies stain negatively for BKV, non-correlated situations between the two tests often lead to a dilemma about how to treat them.MethodsThis retrospective investigation was conducted to determine how real-time quantitative PCR (qPCR) for BKV, routinely applied to serum and urine, could be helpful in identifying the existing BKV in biopsy tissue stained negatively for BKV.ResultsDNA was extracted from each specimen through the use of five 10-μm curls from the tissue block with use of the QIAamp DNA FFPE Tissue Kit (Qiagen), followed by BKV qPCR to determine copies of BKV/μg of biopsy tissue DNA. Group 1 (11 negative renal controls for BKV) demonstrated 0 to 9 BKV copies/μg DNA. Except for 3 focally staining cases showing low BKV, the remaining 10 positive renal controls in group 2 (13 positive transplant biopsies staining positively) demonstrated elevated BKV up to 160 million copies/μg DNA. Group 3 transplants (13 uncertain transplants with negative BKV staining but positive liquid BKV) were negative for BKV (0-12 copies/μg) in 4 of 13, had low BKV copies (36-346 copies/μg) in 5 of 13, and had high BKV copies (17,240-526,945 copies/μg) in 4 of 13 cases, through the use of qPCR.ConclusionsThe data indicate that qPCR from paraffin-embedded tissue as a backup test is sensitive for ruling in/out BKV infection in renal transplant biopsies, particularly in uncertain cases.