Outcomes of screening for BK viraemia and BK nephropathy in renal transplant recipients: A single centre cohort study.

Background and Aims: BK virus is an important cause of renal allograft loss in the renal transplant population. There is limited data regarding intermediate to long-term outcomes in patients with BK viraemia. Effects of routine screening are not well established, with prevalence in prospectively screened cohorts ranging from 11 to 43%. Our aim was to describe the burden of BK viraemia (BKV) and BK nephropathy (BKN) in a large single transplant centre. Method(s): We conducted a retrospective cohort study of 526 patients transplanted between 2008 and 2015, when routine screening (at 3 and 12 months post transplantation) was established. Result(s): 71 patients (13%) developedBKVand 20 (4%) developed BKN during the study period. The median follow-up was 50.9 months (IQR 28.4-82.2) with a minimum follow-up of 12 months. More than 95% of patients were screened for BK at 3 months. All but two patients with BKN had intermediate or high levels of BKV>1000copies/ml. Themajority of patients had basiliximab induction (73%) and maintenance tacrolimus, mycophenolate and prednisolone (94%). Race was strongly associated with BKV (p<0.001), with Asian/ Indian and Aboriginal/Pacific Islander groups both having an increased risk compared to Caucasian (OR Asian/Indian compared to Caucasian 2.49; 95%CI 1.20-5.16). Therewas a trend toward higher rates ofBKV with increasing HLA mismatch (p=0.065). Acute rejection and thymoglobulin use were not associated with BKV (OR 1.16, p=0.751; OR 0.71, p=0.349 respectively). Conclusion(s): BKV was detected in 13%of our cohort and Asian and Indian race was associated with a significantly increased risk. Routine screening for BKV is effective and enables optimal management of immunosuppression to minimise progression.