BK polyomavirus in the urine for follow-up of kidney transplant recipients

Objectives: After kidney transplantation, human BK polyomavirus (BKPyV) can induce a progressive disease, in three stages: viruria, viraemia, and then nephropathy after a few months of viral replication. Therapeutic intervention is recommended when BKPyV is detected in the plasma. The objective of our study was to assess urinary BKPyV nucleic acid test as a predictor for developing viraemia. Methods: We first defined a viruria threshold based on 393 time-matched urine and plasma samples collected after kidney transplantation; to validate this threshold, we followed-up a cohort of 236 kidney transplant patients. Results: A BKPyV viruria threshold of 6.71 log(10) copies/mL best discriminated between plasma-positive and plasma-negative patients (sensitivity 90.9% (95% CI 86.5-95); specificity 90.3% (95% CI 86.3-94.3); area under the curve 0.953 (95% CI 0.933-0.974). In the validation cohort, the risk of developing BKPyV viraemia at 1 year was 16.5% (39/236) and rose to 90.7% (39/43) if BKPyV viruria remained above the threshold of 6.71 for more than 1 month. Conclusions: Sustained BKPyV viruria is a reliable, early marker of patients at high risk of developing BKPyV viraemia. This marker should alert the clinician early, and thus allow timely therapeutic intervention. (C) 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.