The Case for Laboratory Developed Procedures: Quality and Positive Impact on Patient Care

Kaul, Karen L.; Sabatini, Linda M.; Tsongalis, Gregory J.; Caliendo, Angela M.; Olsen, Randall J.; Ashwood, Edward R.; Bale, Sherri; Benirschke, Robert; Carlow, Dean; Funke, Birgit H.; Grody, Wayne W.; Hayden, Randall T.; Hegde, Madhuri; Lyon, Elaine; Murata, Kazunori; Pessin, Melissa; Press, Richard D.; Thomson, Richard B.

BK virus infection is very common, with a seroprevalence in the adult population of *90%. After primary infection, the virus colonizes the renal and urinary tracts; healthy individuals will occasionally shed virus in their urine without consequence. However, in renal transplant recipients, BK virus is the major cause of polyomavirus-associated nephropathy (PVAN), putting 1% to 15% of kidney transplant patients at risk of premature allograft failure. 11 Given the lack of effective antiviral therapy for BK virus, the key to preventing allograft loss is to identify at-risk renal transplant recipients early and reduce immunosuppressive therapy before PVAN develops. Reduction of immunosuppressive therapy helps control viral replication and in most cases prevents the development of PVAN. 12 There is a critical balance between too much immunosuppressive therapy, which can lead to PVAN, and too little immunosuppression causing rejection. The ability to monitor BK virus levels in the blood allows for informed clinical decisions. Studies have shown that monitoring patients with viral load testing during the first 2 years after transplant can dramatically reduce the development of PVAN. Consensus guidelines recommend that screening for BK replication be performed at least every 3 months during the first 2 years posttransplant and then annually until the fifth year posttransplant. 13 When the plasma viral load value rises above a threshold (10 000 to 50 000 copies/mL), a renal biopsy may be performed to assess for PVAN, and immunosuppressive therapy is reduced based on the results of the biopsy. Viral load testing is also done if there is an increase in serum creatinine, as the level of BK virus aids in distinguishing rejection from PVAN.