Prospective screening for BK viremia (BKV) in renal transplant recipients (RTR) may allow earlier detection of BKV reactivation and prevent BKV nephropathy (BKVN). However, utility of long term screening is unknown. Purpose: To determine the incidence and time to BKV with use of protocolized BKV screening. Methods: In Jan 2008, we implemented quantitative BKV plasma screening for all RTR (including kidney-pancreas) patients (pts) at 3,6 and 12 months (mos) then yearly. Detectable BKV was defined as ≥ 2.6 log copies/mL. BKVN was defined as biopsy light microscopy changes consistent with BKVN, positive VP-1 capsid and SV40 immunostaining. RTR received induction with rabbit anti-thymocyte globulin (majority of pts), or basiliximab (low-immunologic risk pts) and maintenance w/ tacrolimus (TAC), mycophenolate mofetil (MMF) and steroids. MMF was discontinued upon BKV detection, followed by TAC dose decrease if BKV persisted. Biopsies were only performed for graft dysfunction. Retrospective analysis was performed for any RTR transplanted Jan 2008-December 2011 who had ≥1 BKV load drawn until June 2012 at a protocol time-point. Results: 622/691 (90%) RTR pts had BKV screening with ≥ 1 value by protocol [473 values at 3 mos, 448 at 6 mos, 394 at 12 mos, 171 at 24 mos, 92 at 36 mos and 10 at 48 mos]. At least 1 BKV ≥ 2.6 log copies/mL occurred in 106 (17%) pts.

A pt with first BKV detected at 24 mos had a negative screen at 12 mos. Two pts first detected at 36 mos had negative screens at 3 and 24 mos respectively. BKV detection/RTR yr for screened pts was: 28 (19%) in 2008, 31 (18%) in 2009, 27(19%) in 2010 and 20 (13%) in 2011 (screened until June 2012). BKVN occurred in 8 pts (1%) during the screening period. Median time to BKVN was 6.5 (2-12 mos) post- transplant and 7/8 (88%) pts had BKV >4.0 log copies/mL at diagnosis. Conclusions: Detection of BKV rates of ≥ 2.6 log copies/mL/year remained consistent from 2008-2010 and BKVN rates remained low. BKV ≥ 2.6 log copies/mL were most often detected at the 3 mo screen. New onset BKV at ≥ 24 mos was rare, questioning the utility of protocol screening beyond 12-24 mos unless renal dysfunction is present. Follow-up is ongoing.

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