Staged Screening of BK Virus-Associated Nephropathy using Urine Cytology and Serum Quantitative Polymerase Chain Reaction: Hong Kong Experience

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IntroductionThis study aims to determine the prevalence/incidence of BK virus viruria, viraemia and BK virus associated nephropathy (BKVAN), and identify risk factors in local renal recipientsMaterials and MethodsKidney transplant recipients who were under the care of our centre were recruited. Recruited patient had urine cytology test. The frequency of tests were determined by their duration of transplantation: every 3 months from the time of transplantation until the end of the first year post-transplantation and then annually till 5-year post-transplant. Additional urine cytology tests were performed in patients after anti-rejection therapy. Quantification of serum BK viral load by qPCR was performed in patient who had urinary decoy cell. In patients who had serum BK viral load >104 copies/ml, allograft biopsy was be arranged for definitive diagnosis of BKVAN.Results467 kidney transplantation patients (268 male, 519 patient-years) were included. 35 patients were transplanted <1 year and 73 patients were transplanted between 1 and 5 year. 16, 7 and 3 patients had urinary decoy, BK viraemia >104 copies/ml and BKVAN respectively. The incident rate of urinary decoy cell, significant viraemia and BKVAN were 3%, 1.6% and 0.6% respectively. 71.4% viraemic (n=7) and all (n=3) BKVAN patients were transplanted within 1 year. 4 (57.1%) viraemic and 2 (66.7%) BKVAN patient receive induction therapy with IL-2R/ATG. All viraemic and BKVAN patients were on mycophenolate based therapy at time of diagnosis. 3 (42.9%) viraemic and 1 (33.3%) BKVAN patients were on cyclosporine A. 4 (57.1%) viraemic and 2 (66.7%) BKVAN patients were on tacrolimus. None of these patients were on mTOR inhibitor.ConclusionsBK virus infection was not uncommon in kidney transplantation in first post-transplant year. Routine BK virus screening with urine cytology and BKV qPCR could identify early infection without evidence of BKVAN.This project is funded by Hong Kong Society of Nephrology.

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