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Purpose: Prospective screening for BK viremia (BKV) post renal transplant (RTR) may prevent BKV nephropathy (BKVN). We sought to: 1) Determine incidence and time to BKV with use of protocolized screening; (2) Examine effect of screening on biopsy proven rejection and BKVN.
Methods: In January 2008, we implemented quantitative BKV plasma screening for all RTR (including kidney-pancreas) patients at 3,6,12 mos then yearly. Detectable BKV was ≥ 2.6 log copies/mL. Patients received induction with rabbit anti-thymocyte globulin (majority of patients), or basiliximab, and maintenance w/ tacrolimus, mycophenolate mofetil (MMF) or enteric coated mycophenolate sodium (ECMS), and steroids. MMF/ECMS was discontinued upon BKV detection, followed by tacrolimus dose decrease if BKV persisted. Biopsies were performed for graft dysfunction. BKVN was defined as light microscopy changes consistent w/ BKVN, and positive VP-1 capsid and SV40 immunostaining. Retrospective analysis was performed for patients transplanted Jan 1, 2008-Sept 31, 2010 who had ≥ 1 BKV results until Dec 31, 2010 and were HIV negative.
Results: Ninety-three percent of 452 patients were screened with: 75%, 66%, 54%, 16% patients having data at 3 6, 12 and 24 months respectively. Nine percent had ≥1 BKV values ≥ 4.0 log/copies/mL, (first detected most often at 3 mos), which has been shown to be associated w/ BKVN. 111 pts transplanted 2005-2007 had biopsies performed during 3 yr pre-screening period vs 111 pts transplanted during screening period. Despite immunosuppression reduction, there was no significant increase in rejection/total RTR patients in pre vs post screening (8% vs 11%, p =0.06). BKV screening decreased BKVN/total RTR patients to 1% from 2% pre-period (p = 0.37). All 5 BKVN patients had BKV ≥4.0 log/copies/mL.
Conclusion: There is currently no effective treatment for BKVN. BKV screening and reduction of immunosuppression did not increase rejection rates and prevented BKVN on clinically indicated biopsies.