A qualitative seminested PCR assay as an alternative to urine cytology for BK polyomavirus screening after renal transplantation.

OBJECTIVE Polyomavirus-associated nephropathy (PVAN) is a major cause of graft dysfunction after kidney transplantation. Therefore, routine screening for BK polyomavirus (BKV) infection with urine cytology or quantitative PCR-based assays has been recommended. Although less expensive than quantitative tests, qualitative PCR assays are not recommended for screening based on the assumption that their diagnostic accuracy is inferior to urine cytology. However, studies comparing the performance of both methods are scarce. METHODS We compared the accuracy between a qualitative seminested PCR (snPCR) assay and urine cytology for the screening of BKV viruria in 104 renal transplant recipients. RESULTS The snPCR assay was more sensitive than cytology (100 and 61%, respectively), yielding better negative predictive value (100 vs. 90%). In 7 (39%) of the 18 PVAN cases, BKV infection was detected exclusively by snPCR. Although the specificity of snPCR (63%) was lower than cytology (74%), their positive predictive values were similar (36 vs. 33%, respectively). In ROC curve analysis, the accuracy of snPCR was significantly higher (p = 0.03). CONCLUSION This qualitative snPCR assay was more accurate than urine cytology for the detection of BKV viruria in renal transplant patients.