PURPOSE: Prior studies have speculated an immunosuppressant therapy (IST) adherence threshold may exist below which renal transplant recipients (RTRs) are at increased risk of graft failure; however, that threshold has yet to be determined. The objective was to use the United States Renal Data System (USRDS) to determine a threshold level of IST adherence below which risk of graft failure in adult RTRs increases significantly.
METHODS: The sample included adult RTRs who were prescribed cyclosporine or tacrolimus and had: primary transplant between Jan 1, 1999 and Dec 31, 2005; graft survival at least 12 months post-transplant; at least 12 months of data in USRDS/Medicare claims; and Medicare coverage for IST. IST adherence was measured by medication possession ratio (MPR). Kaplan-Meier estimates of time to graft failure were compared among MPR quartiles. Cox proportional hazards model was used to evaluate the association between MPR (as a continuous variable) and graft failure and included the covariates race, ethnicity, gender, age at transplant, and donor type.
RESULTS: 31,913 RTRs were included. Kaplan-Meier curves found better graft survival with higher MPR quartiles (Χ2= 51.04, p<0.001). The Cox model found higher MPR values (>0.8) associated with lower graft failure risk and lower MPR values (<0.8) associated with higher graft failure risk. Associations were also found between graft failure and the following (p<0.05): (1) race, as African American RTRs had greater hazard ratios (graft failure risk) versus White RTRs; (2) donor type, as deceased donor transplants had greater hazard ratio versus living donor transplants; and (3) interaction of age at transplant, gender, and donor type, as older female RTRs with living and deceased donors and male RTRs with living donors had lower hazard ratios while male RTRs with deceased donors had no apparent benefit with age.
CONCLUSION: A tentative threshold IST adherence level of at least 0.8, with an optimal level of at least 0.98 (based on prior research), was proposed to reduce risk of graft failure in adult RTRs. Identification of adherence thresholds may help healthcare professionals better target RTRs for interventions to improve IST adherence and graft survival.
To cite this abstract in AMA style:Spivey C, Chisholm-Burns M, Damadzadeh B, Billheimer D. Determining Threshold Immunosuppressant Adherence Levels To Reduce Graft Failure Risk among Adult Renal Transplant Recipients [abstract]. Am J Transplant. 2013; 13 (suppl 5). https://atcmeetingabstracts.com/abstract/determining-threshold-immunosuppressant-adherence-levels-to-reduce-graft-failure-risk-among-adult-renal-transplant-recipients/. Accessed May 6, 2021.
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