Polymerase Chain Reaction Detection of BK Virus and Monitoring of BK Nephropathy in Renal Transplant Recipients at the University Hospital La Fe

IntroductionReactivation of BK infection occurs in immunocompromised hosts causing tubulointerstitial nephropathy (BKVN). Approximately 5% of kidney transplant recipients (KTR) develop BKVN, special half of whom lose their grafts. However, BKVN morphologic diagnosis on a renal biopsy is complicated, because the cytopathic changes can sometimes mimic rejection. Thus, BKV DNA–polymerase chain reaction (PCR) assay on serum, urine, and renal tissue is useful for early detection and monitoring of BKV.Materials and methodsWe performed routine monthly urine cytologies looking for decoy cells as a marker of virus replication. Then, we performed a qualitative PCR on urine and serum in all recipients (independently of positive or negative cytology). We amplified 3 BK viral genome regions, LT (early transcription region) and VP1 (late transcription region) seeking a more accurate virus detection, and the TCR (control transcription region) region to perform a polymorphism sequence analysis to identify the BK genomic variant. Finally, the BKVN diagnosis was confirmed using renal biopsy.ResultsAt present, 132 patients have been monitored. Thirteen of 40 (33%) were PCR-urine–positive cases (5 LT+/VP1− and 8 LT+/VP1+), and 10 of 132 (7.5%) were PCR-serum–positive cases (7 LT+/VP1− and 3 LT+/VP1+). When we compared PCR-urine and cytology results, 11 of 40 (27.5%) patients showed a positive cytology, 6 of whom were PCR- urine–positive (1 LT+/VP1− and 5 LT+/VP1+); whereas, 29 patients showed a negative cytology, 7 of whom were PCR-urine–positive(3 LT+/VP1− and 4 LT+/VP1+). Thus, comparison of PCR- urine and cytology results revealed false-positive and false-negative cases. Finally, TCR sequence analysis was performed in 9 patients to identify the BK genomic variants.ConclusionTesting for BKV DNA in urine and serum is a noninvasive early detection assay and monitoring tool.