Participants
This study analyzed 643 cases of living-donor kidney transplantations performed between 1 January 1997 and 31 December 2021, at participating facilities, including Iwate Medical University Hospital. Using a shared database, the outcomes of kidney transplantations with blood- and non-blood-related donors were retrospectively examined. Furthermore, in spousal kidney transplantations, the outcomes of WTH and HTW transplantations were analyzed independently. As the six participating facilities were not affiliated, their immunosuppressive drug regimens and doses were not identical. However, all facilities primarily used TAC as the primary calcineurin inhibitor (CNI) and introduced a regimen of four drugs (TAC, methylprednisolone, basiliximab, and mycophenolate mofetil) during the perioperative period. Additionally, various recipient-related factors were included in the analysis, including age, sex, body mass index (BMI), presence of comorbidities including diabetes and hypertension, history of renal replacement therapy, blood relation to the donor, presence of ABO incompatibility, number of HLA mismatches, type of CNI used, results of flow cytometric panel reactive antibody assay (PRA), presence of donor-specific antibody (DSA), plasmapheresis status, use of rituximab (RIT), use of everolimus (EV), occurrence of transplant rejection, and occurrence and time to graft loss. Rejection was defined on the basis of the clinical diagnosis of rejection, which is based on each facility’s criteria and does not necessarily require histopathology, and required therapeutic intervention. Donor-related factors such as age, sex, BMI, preoperative renal function, height, weight, estimated glomerular filtration rate (eGFR), serum creatinine level, donor kidney side (left or right kidney), method of donor nephrectomy, kidney weight, and the presence and types of marginal donor factors were also included in the analysis. The marginal donor-related factors refer to those that may affect the suitability of a donated kidney for transplantation. These factors included age ≥ 70 years, presence of hypertension, presence of diabetes, BMI ≥ 30 kg/m2, and creatinine clearance rate ≤ 80 mL/min or an eGFR ≤ 70 mL/min.
Statistical analyses
Propensity score matching on the bais of various recipient- and donor-related factors were used to compare the engraftment periods of transplantations with blood- and non-blood-related donors. These factors included recipient age, BMI, presence of diabetes, history of renal replacement therapy, presence of ABO incompatibility, number of HLA mismatches, type of CNI used, use of RIT, use of EV, donor age, eGFR, BMI, kidney side, and presence of marginal donor-related factors. Based on these factors, 84 cases were selected from blood- and non-blood-related transplantation groups. Similarly, 58 cases each were selected from the WTH and HTW groups, and the engraftment periods were compared. Engraftment period was analyzed using the Kaplan–Meier method, and intergroup clinical factors were analyzed using the log-rank test. The analyses were conducted using JMP version 14.0.0 (JMP Statistical Discovery, Cary, NC, USA), and statistical significance was set at p < 0.05.
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