Diagnostic accuracy of blood qualitative nucleic acid testing for polyomavirus-associated nephropathy in kidney recipients

Aim: Polyomavirus-associated nephropathy (PVAN) is an important cause of graft loss following kidney transplantation and may only be diagnosed with kidney transplant biopsy. Early detection may improve outcomes by enabling early intervention. Serum polyomavirus polymerase chain reaction (PVPCR) has been used to identify patients at risk of PVAN, but prior studies have not assessed all patients with negative PVPCR with transplant biopsy, potentially overestimating test performance. Methods: We assessed the diagnostic accuracy of qualitative PVPCR for detection of PVAN in a population undergoing protocol biopsies. We included all patients receiving kidney or kidney-pancreas transplants and followed at Westmead Hospital, Sydney, Australia, between May 2002 and March 2007, excluding those with graft loss prior to 1 month post transplant or without PVPCR testing in the first 12 months. We compared PVPCR to contemporaneous transplant biopsies assessed with light microscopy and immunohistochemistry. Results: Of the 257 included patients, 246 (96%) underwent biopsy within 30 days of PVPCR. Eight of 36 patients with positive PVPCR had PVAN and one of 210 patients with negative PVPCR had PVAN. The point prevalence of PVAN was therefore 3.7%, with PVPCR sensitivity 89% (95% CI 57% to 99%) and specificity 88% (95% CI 83% to 92%). The negative predictive value is 99.5% (95% CI 97.3% to 100.0%). Conclusion: Qualitative PVPCR on serum is a reliable triage test for excluding the presence of PVAN. Screening for PVAN need not include biopsy in patients with negative PVPCR.