Most calcineurin inhibitor (CNI)‐based protocols reduce blood trough goals approximately 2–3 months post‐transplant in clinically stable kidney transplant recipients. The CNI target trough level to prevent rejection, after reduction, is unknown. Using a multivariate Cox proportional hazards model, we determined the association of time‐varying tacrolimus (TAC) trough levels with acute rejection (AR) occurring in the first 6 months post‐transplant, but specifically we assessed this association after 3 months. A total of 1930 patients received TAC‐based immunosuppression prior to AR in a prospective study. Of the 151 (7.8%) who developed AR, 47 developed AR after 3 months post‐transplant. In an adjusted time‐varying multivariate model, each 1 ng/ml decrease in TAC trough levels was associated with a 7.2% increased risk of AR [hazards ratio (HR) = 1.07, 95% confidence interval (CI) (1.01, 1.14) P = 0.03] in the first 6 months. There was an additional 23% increased risk of AR with each 1 ng/ml decrease in the TAC trough levels in months 3–6 [HR = 1.23, 95% CI (1.06, 1.43) P = 0.008]. In conclusion, lower TAC trough levels were significantly associated with increased risk of AR in the first 6 months post‐transplant with additional risk of AR between months 3 and 6 post‐transplant. The timing and practice of TAC dose reduction should be personalized based on the individual's risk factors.

The performance of glomerular filtration rate (GFR) equations incorporating both cystatin C (CysC) and serum creatinine (Creat) in living kidney donors has not been studied before. From a population of 3,698 living kidney donors, 257 donors were randomly selected to undergo GFR measurement (mGFR) by the plasma disappearance of iohexol. GFR was estimated with the Modification of Diet in Renal Disease (MDRD) equation and the Chronic Kidney Disease Epidemiology Collaboration study eGFR(CKD-EPI-Creat) in 257 donors and the two newly developed equations using CysC with and without Creat, eGFR(CKD-EPI-CysC) and eGFR(CKD-EPI-Creat+CysC), in 215 donors. Mean mGFR was 71.8±11.8 mL/min/1.73 m. The eGFR(MDRD) exhibited least and only negative bias and the three other models were comparable in terms of bias. The eGFR(CKD-EPI-Creat+CysC) equation was most precise; r=0.64. Both eGFR(MDRD) and eGFR(CKD-EPI-Creat+CysC) had high percentage (94.4% and 92.6%, respectively) of estimates falling within 30% of mGFR versus estimates by eGFR(CKD-EPI-Creat) and eGFR(CKD-EPI-CysC) equations (87.2% and 85.1%, respectively). The eGFR(MDRD) was by far most accurate in identifying those with mGFR less than 60 mL/min/1.73 m whereas the CKD-EPI models were extremely accurate in classifying those with mGFR greater than or equal to 60 mL/min/1.73 m. eGFR(CKD-EPI-Creat+CysC) equation provides comparable accuracy to the eGFR(MDRD) in overall estimation of mGFR, but with higher precision. However, eGFR(CKD-EPI-Creat+CysC) clearly misses many of those with a post-donation GFR less than 60 mL/min/1.73 m and therefore eGFR(MDRD) is preferable in detecting donors with GFR less than 60 mL/min/1.73 m.

Background.: Steroid avoidance in kidney transplantation has been proven noninferior. Long-term outcome data on steroid avoidance in simultaneous pancreas-kidney (SPK) remains scant. Methods.: Utilizing the Scientific Registry of Transplant Recipients between 2000 and 2020, we studied all primary crossmatch negative SPK recipients (N = 5683) who received antithymocyte globulin induction and were discharged alive with functioning grafts on tacrolimus and mycophenolate ± steroid maintenance. Recipients were grouped according to steroid use into 2 groups: steroid maintenance (n = 4191) and steroid avoidance (n = 1492). Kaplan-Meier curves censored at 10 y were generated for recipient and allograft survival by steroid maintenance. Predictors for recipient and graft survival were examined using Cox Proportional Hazards. Models were adjusted for age, body mass index, ethnicity, diabetes type, human leukocyte-antigen mismatches, cold ischemia time, transplant era, preemptive transplantation, and pancreas donor risk index with the transplant center included as a random effect. Results.: Steroid avoidance gained popularity over time, accounting for over one-fourth of the studied cohort. One-year acute rejection rates by steroid avoidance were comparable for kidney (8.6% versus 9%, P = 0.783); however, the pancreas rejection rate was lower in the steroid avoidance group (7.9% versus 10%; P = 0.035). After adjustment, steroid avoidance did not influence recipient survival (lower level of confidence interval, adjusted hazard ratio, upper level of confidence interval: 0.94, 1.15, 1.39), pancreas (0.75, 0.93, 1.16), or kidney (0.95, 1.18, 1.45) death-censored survival, compared with steroid maintenance. Conclusions.: Accounting for the recipient and graft characteristics, steroid avoidance is associated with similar recipient, pancreas, and kidney graft outcomes compared with steroid maintenance in SPK recipients after antithymocyte globulin induction with tacrolimus and mycophenolate maintenance.