Real-time RT-PCR assay for the quantitation of polyomavirus BK VP1 mRNA levels in urine.

In renal transplant recipients, polyomavirus BK can reactivate resulting in graft nephropathy. Screening for BK virus replication may allow for earlier interventions with reduced allograft loss. The measurement of urinary cell BKV VP1 mRNA for identify viral replication levels at risk of developing nephropathy has been proposed. In this article, the development, optimization, and standardization of a Taqman real-time RT-PCR assay for the quantitation of BKV VP1 mRNA levels in urine is described. Subsequently, the method has been validated on urine specimens obtained from renal transplant recipients. The use of VP1 mRNA measurement as a marker for viral replication and a tool for noninvasive diagnosis of nephropathy should be regarded with great caution, given the potentially limited positive predictive value and the drawbacks associated with the complexity of the real-time RT-PCR assay requiring an expert well trained operator and the relatively poor cost-efficiency ratio.