Removal Of Anti-Thymocyte Globulin By Plasma Exchange In Abo-Incompatible And Positive Crossmatch Kidney Transplant Recipients

Background. Recipients of ABO-incompatible (ABOI) and positive crossmatch (PXM) kidney transplants are at high risk for antibody-mediated acute rejection. Despite aggressive immunosuppression in high-risk patients, the incidence of acute rejection remains considerably higher than in other groups. No published studies have examined plasma concentrations of anti-thymocyte globulin (ATG) in patients undergoing plasma exchange. The objectives of this study were to compare plasma ATG concentrations before and after plasma exchange in ABOI and PXM kidney transplant patients to determine the amount removed. Materials and Methods. This prospective pharmacokinetic evaluation enrolled 10 patients undergoing ABOI or PXM kidney transplant at an academic medical center. Blood and waste plasma samples from 5 patients were assayed for total and active ATG concentrations. Patient records were monitored for renal function and rejection rates in the first 6 months post-transplant. Results. Total ATG concentrations decreased a mean of 59.78 +/- 13.91% after each plasma exchange session, and active ATG levels decreased a mean of 56.8 +/- 17.08%. Mean daily concentrations reflect a lack of expected ATG accumulation. Only 1 of 4 patients had detectable ATG concentrations after 30 days. After 6 months, the incidence of acute rejection in this sample was 44% and graft survival was 89%. Conclusions. This is the first study to show that plasma exchange removes a substantial amount of ATG in high-risk kidney transplant patients. Based on these results, we believe these high-risk patients have been traditionally underdosed.