NDT Advance Access published online on May 25, 2008
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn289
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Monitoring of BK virus replication in the first year following renal transplantation
1 Dipartimento di Sanità Pubblica e Microbiologia, Laboratorio di Virologia, Università di Torino 2 Dipartimento di Medicina Interna, Unità Trapianto Rene, Ospedale Molinette, Torino, Italy
Correspondence and offprint requests to: Cristina Costa, Dipartimento di Sanità Pubblica e Microbiologia, Laboratorio di Virologia, Università di Torino, Italy. E-mail: cristina.costa{at}unito.it, rossana.cavallo{at}unito.it
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Abstract |
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Background. BK virus-associated nephropathy (BKVAN) is one of the most common viral diseases affecting renal allografts. Screening for viral replication may allow for earlier intervention with reduced allograft loss. A plasma viral load >104 copies/mL of BKV DNA is recommended for a presumed diagnosis of BKVAN.
Methods. We monitored BKV load on serum and urine samples by Real-Time TaqMan PCR in 229 renal transplant recipients in the first year post-transplantation. Overall, 2025 serum and 2025 urine samples were evaluated. A graft biopsy was performed in 47/229 patients to investigate the declining renal function. Operating characteristics [sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV)] and receiver operating characteristic (ROC) curve analysis at different viral load values were calculated.
Results. Serum BKV viral load was >104 in 5/229 patients (2.2%). A histological diagnosis of BKVAN was made in 3/229 patients (1.3%): 3/5 (60.0%) among those with serum viral load >104 and 3/4 (75.0%) in those with >1.6 x 104. Operating characteristics of a serum BK load of 104 for the diagnosis of BKVAN were as follows: sensitivity, 100%; specificity, 99.1%; NPV, 100%; PPV, 59.4%. Specificity and PPV rose to 99.6% and 75.0% when using a cut-off level of 1.6 x 104 copies/mL.
Conclusions. The recommended level of BK viraemia of 104 copies/mL is useful to identify patients at risk of BKVAN, although specificity and PPV increase by using a cut-off level of 1.6 x 104 copies/mL. BK replication may occur in the first 3 months post-transplantation and subsequently recede. Therefore, the temporal profile of BKV replication has to be accurately evaluated and occasionally elevated values should prompt a closer monitoring.
Keywords: BKV-associated nephropathy; monitoring; polyomavirus BK; renal transplantation
* Cristina Costa and Massimiliano Bergallo equally contributed to this work and share first authorship.
Received for publication: 7. 2.08
Accepted in revised form: 24. 4.08