(B-083) Use of Belatacept and Tacrolimus Among Kidney Transplant Recipients From 2011-2020: Comparing United States Renal Data System (USRDS) and Scientific Registry of Transplant Recipients (SRTR)

Background: Tacrolimus is the most prescribed immunosuppressant medication post-kidney transplant in the US and is taken orally 1-2 times daily. Belatacept, an infrequently prescribed immunosuppressant, is administered as monthly injection. Belatacept may improve adherence and reduce nephrotoxicity compared to tacrolimus. Discrepant outcomes have been reported between United States Renal Data System (USRDS) and Scientific Registry of Transplant Recipients (SRTR). However, limited evidence exists concerning the initiation of immunosuppressant medications among kidney transplant recipients (KTRs) across these databases.

Objectives: To describe use of belatacept and tacrolimus and compare the results using USRDS and SRTR, the two primary data sources for KTRs in the US..

Methods: We linked data from USRDS and SRTR to assemble a cohort of adult KTRs who received their first kidney transplant from 2011 to 2020, had primary Medicare coverage for ≥6 months before transplant, and had a claim for a maintenance immunosuppressant medication within 45 days post-transplant. We excluded KTRs with simultaneous, prior or multi-organ transplant or without Epstein-Barr virus seropositive status. We calculated the use of belatacept and tacrolimus within 45 days post-transplant, and we assessed the concordance of USRDS and SRTR using kappa statistics and 95% confidence intervals (CIs). We conducted sensitivity analyses using 7-, 14-, 30-, and 60-day post-transplant landmarks.

Results: Among 35,522 KTRs, the median age was 56 years (interquartile range (IQR): [45, 65]), and median cold ischemic time was 15 hours (IQR: 9, 22), 61% were male, and 86% received kidneys from deceased donors. The number (%) of new users of belatacept only, belatacept-tacrolimus and tacrolimus only within 45 days post-transplant were 697 (2%), 518 (1.5%), and 33,421 (94%), respectively in USRDS compared to 538 (1.5), 1,490 (4.2), and 32,608 (91.8), respectively in SRTR. Overall concordance at the 45-day landmark was 96% (kappa =0.66, 95% CIs: 0.64, 0.68). Using landmarks at 60, 30-, 14- and 7- day, concordance remained 95%-96% but kappa (95% CIs) were 0.66 (0.64,0.67), 0.64 (0.62, 0.66), 0.50 (0.47, 0.53), and 0.34 (0.30, 0.38), respectively.

Conclusions: Concordance between USRDS and SRTR was high, particularly for the 45-, 60-day landmark compared to shorter ones. Future studies could explore and quantify causes of disagreement. For example, receipt of belatacept through participation in clinical trials may not be captured in USRDS. Some discordance might also stem from early prescription changes due to adverse events.