Trajectories of Medication Adherence in Pediatric Organ Transplantation and Their Relationship to Posttransplant Health Outcomes Project Summary / Abstract Non-adherence to immunosuppressive medication remains one of the most significant predictors of late acute rejection (LAR), increased number and frequency of hospitalizations, need for retransplantation, and even mortality in pediatric transplant patients. Medication Level Variability Index (MLVI) has been validated as a measure of medication adherence and calculated from medication blood levels obtained during routine clinical care of these patients. However, few studies have examined longitudinal trajectories of adherence to immunosuppressive medication and possible differences in posttransplant outcomes. Further research is necessary to understand variation in trajectories of medication adherence in pediatric organ transplantation with Growth Mixture Modeling (GMM) proposed as a novel statistical approach. We propose to address these gaps in knowledge by examining trajectories of MLVI values in data collected from one of the largest pediatric transplant centers in the country. Patient and administrative data from the United Network for Organ Sharing (UNOS, U.S. Department of Health and Human Services) will be electronically linked with patient electronic health records (EHR). We will use latent growth curve analysis and a novel GMM three-step approach to this analytic technique to 1) examine the association between patient and familial risk factors and long-term posttransplant health outcomes, 2) estimate the functional form medication growth trajectories, 3) examine the number of classes of growth in MLVI values and identify patients with similar classes, and 4) examine association between classes of growth and both patient- and family-level predictors and posttransplant health outcomes. Understanding the patient- and family-level predictors of classes of individual growth will inform assessment and intervention efforts as to which patients and families may be greatest risk for non-adherence over time and poor posttransplant outcomes. Results aim to be applicable to national pediatric organ transplant centers, other areas of chronic illness in childhood and adolescence, and the basis for future research and development of interventions.