Long-term immunosuppression adherence after kidney transplant and relationship to allograft histology

Background. Nonadherence to immunosuppression after kidney transplant is an important contributor to graft failure. Little is known about how nonadherence changes 3 years posttransplant when Medicare coverage of immunosuppression ends and how that nonadherence impacts allograft histology. The goal of this study was to compare rates of nonadherence during posttransplant years 1 to 3 to years 3 to 5 and examine the relationship between nonadherence during years 3 to 5 and 5-year allograft histology. Methods. We retrospectively analyzed 552 conventional kidney allografts in patients transplanted at our center between January 1, 1999, and June 1, 2010, who used the Mayo Clinic Specialty Pharmacy for the first 5 years posttransplant. Nonadherence was defined as less than 80% proportion of days covered. Overall adherence to immunosuppression appeared to be higher during years 3 and 5 compared to between years 1 and 3 (89.4% vs 82.9%, respectively; P < 0.0001 [paired t test]). Results. Overall nonadherence during posttransplant years 3 to 5 appeared to be associated with fibrosis and inflammation on 5-year allograft biopsy but not with transplant glomerulopathy (16.9% vs 5.9%, P = 0.004; 10.4% vs 8.5%, P = 0.61, respectively). After adjusting for nonadherence to calcineurin inhibitor and prednisone therapy, only nonadherence to antimetabolite therapy remained significantly associated with 5-year fibrosis and inflammation (odds ratio, 10.6; 95% confidence interval, 1.5-76.1; P = 0.02). Conclusions. Efforts to improve long-term adherence, possibly through the use of specialty pharmacies and increased adherence to antimetabolite therapy, may improve long-term allograft histology and survival, although further studies are needed to confirm these findings.