Diagnostic utility of urine cytology in early detection of polyomavirus in transplant patients

Polyomavirus-associated nephropathy (PVAN) is one of the most common disease affecting transplant patients, mainly caused by BK polyomavirus (BKV) and with5% of the cases caused by JC polyomavirus (JCV). Screening and early intervention, including appropriate reduction in immunosuppressive therapy, are critical to reduce allograft loss. The presence of decoy cells in the urine is a characteristic cytopathic effect of polyomavirus. The goal of this study was to investigate the significance of decoy cells in urine cytology in transplant patients, comparing with the plasma viral replication level detected by the real-time quantitative BK virus polymerase chain reaction test (Qt-BK PCR).A cohort of post-transplantation patients with serum BKV level monitored by Qt-BK PCR from 2008 to 2013 was studied. Among them, 35 patients had both urine cytology (UC) analysis and Qt-BK PCR performed. The clinical presentation along with the available UC slides were retrieved and reviewed.Compared with Qt-BK PCR, the sensitivity, specificity, positive predictive value, and negative predictive value of urine cytology analyzed within one week apart were 92%, 71%, 85%, and 83%, respectively. The accuracy of the UC was 84%. More interestingly, UC played a key role in identifying a case of JCV associated PVAN whereas Qt-BK PCR from both urine and plasma failed to detect this virus.Our data suggests that urine cytology is a sensitive surveillance test for early detection of polyomavirus in transplant patients, and it is particularly useful to screen for rare JC polyomavirus.