Repeat true surveillance biopsies in kidney transplantation.

Background. Protocol biopsies are assigned to fixed points in time after transplantation irrespective of renal function. Usually, it is not known whether there is graft dysfunction at the time of biopsy. This study analyzes repeat protocol biopsies in the absence of any clinical signs of graft dysfunction at the time of biopsy (i.e., "true surveillance biopsy"). Methods. Observational single center study. Kidney transplant recipients with protocol biopsies after 3 and 6 months were analyzed. Results. Three hundred seventy patients had protocol biopsies after 3 and 6 months. One hundred forty-eight patients (40%; 296 biopsies) with a median follow-up of 3.4 years (range, 0.95-7.7 years), fulfilled the criteria of repeat true surveillance biopsies. Graft survival censored for death was 100% at 1 year, 96% at the end of follow-up. One hundred eighty-four biopsies (62%) revealed pathological findings, mainly subclinical rejection (3/6 months: 41% vs. 45%; P = 0.2) and chronic lesions (3/6 months: 22% vs. 44%; P<0.001). Grafts with repeat pathological findings at 3 and 6 months had a significant decline in graft function at end of follow-up compared with grafts with no or only singular pathology (median delta estimated glomerular filtration rate: -10.24 vs. -0.19; P = 0.005). Ninety-three of 148 patients (63%) had a therapeutic intervention as a consequence of the biopsy. Conclusions. Less than 50% of protocol biopsies were performed in the absence of any clinical signs of graft dysfunction. A high proportion of these biopsies revealed pathological findings that were associated with a significant decrease in long-term graft function.