Clinical courses of renal transplant recipients with high BK viremia

We sought to investigate the clinical courses of renal transplant recipients with plasma BK viral loads >10(4) copies/mL.

A single-center retrospective review was performed of 88 kidney transplant patients in whom high BK viremia (defined as plasma BKV load >10(4) copies/mL) was detected more than once from January 1, 2004, to December 31, 2011.

At the time of transplantation, the mean recipient and donor ages were 44.5 ± 11.1 and 43.9 ± 11.3 years, respectively, and 59 subjects (67.0%) were male. The median times to first BK positivity and high BK viremia after transplantation were 44 and 136 days, respectively. Within 3 months after transplantation, we detected, 56 cases of high BK viremia (63.6%). The mean duration of high BK viremia was 8.2 ± 7.7 months. When plasma BKV load was first >4 logs, the mean log BKV load was 5.50 ± 1.11 log copies/mL, which rose to a maximum of 5.82 ± 1.11. At these times, mean serum creatinine concentrations were 1.67 ± 0.79 and 2.64 ± 2.78 mg/dL, respectively. There were 31 cases (35%) of biopsy-proven BK nephropathy patients among 51 (58%) biopsies. Treatment modalities included discontinuation or dose reduction of mycophenolic acid drugs (n = 68) and switch from tacrolimus to cyclosporine (n = 9), cidofovir (n = 9), and leflunomide (n = 3). Based on the serum creatinine elevation after high BK viremia, patients were divided into group 1 (n = 27; 30.1%), whose maximal creatinine change was <0.5 mg/dL, and group 2, with a greater alteration. On multivariate logistic regression analysis, the maximal plasma BK viral load was significantly associated with a greater serum creatinine elevation (P < .001).

High BK viremia mostly occurred within 3 months after kidney transplantation. About 30% of renal allograft recipients with high BK viremia maintained stable renal function. Maximal plasma BK viral load was the only independent risk factor for high serum creatinine elevation.