Management of BK Virus Infection in Kidney Transplant Recipients

Diagnosis and Screening Protocol

Regular quantitative BK viral load monitoring is recommended for all kidney transplant recipients, using nucleic acid-based viral load assays of urine and/or blood, according to the American Journal of Transplantation 1, 2
Screening schedule should include monthly monitoring for the first 6 months post-transplant, testing at months 9 and 12, every 3 months during the second year, and annually thereafter, as recommended by the American Journal of Transplantation 2, 3
Additional testing should be performed for any unexplained rise in serum creatinine, as suggested by the American Journal of Transplantation 1, 2

BK virus infection is defined as quantitative BK viral DNA load in blood or urine above the detection threshold, and should be classified as either BK viruria, viremia, or both, according to the American Journal of Transplantation 1, 4
Viremia is more predictive of BKVAN than viruria alone, as reported by the American Journal of Transplantation 1, 2
Proven BKVAN requires renal biopsy showing acute tubular necrosis-like picture, interstitial nephritis mimicking rejection, or chronic allograft nephropathy, with confirmation of BK virus by electron microscopy, immunohistochemistry, or in-situ hybridization, as described by the American Journal of Transplantation 1, 4

Regular monitoring of BK viral load to assess response to immunosuppression reduction is recommended, along with concurrent monitoring of renal function to detect potential rejection, as suggested by the American Journal of Transplantation 1, 2
Repeat kidney biopsy may be necessary if renal function continues to deteriorate despite viral load reduction, according to the American Journal of Transplantation 1

BK virus infection is not limited to kidney transplant recipients; native kidney involvement can occur in recipients of non-renal solid organs, as reported by the American Journal of Transplantation 1, 5
Children may experience primary BK infection rather than reactivation, according to the American Journal of Transplantation 1, 5
The emergence of BKVAN is associated with more potent modern immunosuppressive regimens, as described by the American Journal of Transplantation 1

Relying solely on urine cytology (decoy cells) without confirmatory PCR testing may lead to false positives, as warned by the American Journal of Transplantation 1, 2
Mistaking BKVAN for acute rejection on biopsy can lead to inappropriate increased immunosuppression, worsening BK infection, according to the American Journal of Transplantation 1, 4