Significance of Functional Graft Survival Rate

Kim, Myoung Soo; Kim, Yu Seun; Cho, Ok Ku; Kim, Soon Il; Chung, Ku Yong; Oh, Chang Kwon; Moon, Jang Il; Han, Dae Suk; Park, Kiil

Abstract

Patient death with a functioning graft(DFG) has been a predominant cause of graft loss. According to conventional graft survival(C-GS) analysis, DFG is considered as a graft failure. However, such survival analysis may obscure immunologic graft loss and distort the overall graft results as well as risk factors affecting the graft survivals. In functional graft survival(F-GS) analysis, the DFG is considered as censored data(in which the graft survived until patient death) which is more closely related with the immunologic graft loss. We designed our study to identify the differences and significance of F-GS compared to C-GS. From April 1984 to October 1995, 1242 living donor kidney transplantations under cyclosporine were performed at Yonsei University Medical Center. At least a 1-year follow-up was possible in all the patients. The graft survival rate was calculated by both C-GS and F-GS analyses. The recipient's and the donor's ages, the donor-recipient relationship, the degree of HLA matching, the degree of ABO blood type matching, the episodes of acute rejection within 1 year, and the presence of diabetes mellitus were monitored as risk factors affecting the graft survival in the two analysis methods. Univariate and multivariate analyses for risk factors were done by the Kaplain-Meier method and the Cox proportional harzard model. The C-GS rate were 96.3% at 1 year, 81.8% at 5 years, and 58.4% at 10 years compared to 98.5%, 88.1%, and 67.9%, respectively in the F-GS analysis. Elderly recipients(> or =50), elderly donors(> or =50), presence of acute rejection within 1 year post-transplant, ABO blood type minor mismatching, and diabetic recipients were risk factors affecting long-term graft survival in the C-GS analysis. However, elderly recipients and diabetic recipients were no longer considered as risk factors in the F-GS analysis. In fact, elderly recipients or diabetic recipients showed equal or even better graft survivals in the F-GS analysis compared with younger or non-diabetic recipients. The differences between the C-GS and the F-GS analyses in such subgroups suggests that the primary cause of graft loss in these groups was non-immunologic. Death with functioning graft(DFG) needs to be considered in analyzing kidney-transplant outcomes. Hence, we propose that all transplant graft survival data be presented in two ways, by conventional and functional graft analyses.