Age-related differences in rejection rates, infections and tacrolimus exposure in pediatric kidney transplant recipients in the CERTAIN registry

Abstract Introduction Data on age-related differences in rejection rates, infectious episodes and tacrolimus exposure in pediatric kidney transplant recipients (pKTR) on a tacrolimus-based immunosuppressive regimen are scarce. Methods We performed a large-scale analysis of 802 pKTR from the CERTAIN registry from 40 centers in 14 countries. Inclusion criteria were a tacrolimus-based immunosuppressive regimen and at least two years of follow-up. The patient population was divided into three age groups (infants and young children <6 years, school-aged children 6-12 years, and adolescents >12 years) to assess age-related differences in outcome. Results Median follow-up was 48 months (IQR, 36-72). Within the first 2 years post-transplant, infants and young children had a significantly higher incidence of infections (80.6% vs. 55.0% in adolescents, P<0.001) and a significantly higher number of cumulative hospital days (median 13 days vs. 7 days in adolescents, P < 0.001). Adolescents had a significantly higher rate of biopsy-proven acute rejection episodes in the first year post-transplant (21.7%) than infants and young children (12.6%, P=0.007). Infants and young children had significantly lower tacrolimus trough levels, lower tacrolimus concentration-to-dose ratios as an approximation for higher tacrolimus clearance, and higher tacrolimus intra-patient variability (all P < 0.01) than adolescents. Conclusions This largest study to date in European pKTR on a tacrolimus-based immunosuppressive regimen shows important age-related differences in rejection rates, infection episodes, tacrolimus exposure and clearance. These data suggest that immunosuppressive therapy in pKTR should be tailored and personalized according to the age-specific risk profiles of this heterogeneous patient population. The data may also serve as a benchmark for future studies with novel immunosuppressive drugs.