Screening for polyomavirus associated nephropathy in renal transplantation with blood viral load measurement

BackgroundPolyomavirus associated nephropathy (PVAN) is an important cause of graft failure in the renal transplant population. It has been shown that viremia precedes PVAN, suggesting that measurement of blood viral load could be used for PVAN screening.ObjectivesTo verify the utility of BK virus (BKV) blood viral load measurement for PVAN screening in the renal transplant population, establish a threshold value, and determine the sensitivity and specificity of the test.Study designWe developed a real-time PCR assay for BKV blood viral load measurement and included this assay in the PVAN screening protocol of the renal transplant recipients of our institution. We report results for 60 patients who had a blood viral load measurement concomitantly with an allograft biopsy with immunohistochemistry for polyomavirus.Results14 patients were found to have a PVAN on allograft biopsy together with a viral load above 3.0 × 103 copies/ml. None of the patients with a viral load under 3.0 × 103 copies/ml had a PVAN on allograft biopsy. The area under the receiver operating characteristic (ROC) curve was 0.95 (95% CI: 0.91–1.00) and using a threshold value of 3.0 × 103 copies/ml yielded a sensitivity of 100% (95% CI: 76.8–100%) and a specificity of 89.6% (95% CI: 77.3–96.5%) for PVAN screening.ConclusionsBKV blood viral load measurement is sensitive and specific for PVAN screening when a threshold value is precisely determined.