Influence of surveillance renal allograft biopsy on diagnosis and prognosis of polyomavirus-associated nephropathy

Background. Polyomavirus-associated nephropathy (PVAN) is an increasingly prevalent cause of allograft dysfunction. Methods. In 18 histologically proven cases of PVAN managed by reduced immunosuppression, monitoring of serum creatinine, and repeated biopsy, graft outcomes were correlated with clinical and histologic indices. Six months postdiagnosis the status of each graft was classified as poor (N = 7) or satisfactory (N = 11). Poor transplant status was defined as graft loss, increased severity of PVAN on repeat biopsy, or serum creatinine >3.0 mg/dL. Diagnosis resulted from either surveillance allograft biopsies (N = 8) or biopsies performed for increased serum creatinine (nonsurveillance, N = 10). Results. The surveillance biopsy group was more likely than the nonsurveillance group to have satisfactory graft status at 6 months (eight of eight vs. three of ten, P = 0.004) and had significantly lower serum creatinine at diagnosis, 3, and 6 months. Histologic scoring for chronic interstitial and tubular injury was lower in diagnostic surveillance biopsies compared to non-surveillance biopsies (P = 0.01). Satisfactory transplant status was also associated with reduced or absent virus on repeat biopsy (P = 0.01). Poor transplant status was associated with a higher frequency of recipient^neg/donor^pos cytomegalovirus (CMV) serology (71% vs. 9%, P = 0.01). Conclusion. Surveillance allograft biopsy provides an important means for earlier detection of PVAN and permits timely alterations to immunosuppression. Early diagnosis is associated with a lesser degree of interstitial fibrosis at diagnosis and lower baseline and subsequent serum creatinine.