Evaluation of tools for annual capture of adherence to immunosuppressive medications after renal transplantation - a single-centre open prospective trial.

Annual assessment of adherence would strengthen long-term outcome assessments from registry data. The objective of this study was to evaluate tools suitable for annual routine capture of adherence data in renal transplant recipients. A single-centre open prospective trial included 295 renal transplant recipients on tacrolimus. Two-thirds of the patients were included 4 weeks post-transplant, randomized 1:1 to intensive or single-point adherence assessment in the early phase and 1-year post-transplant. One-third were included 1-year post-transplant during a cross-sectional investigation. Adherence was assessed using multiple methods: The "Basel Assessment of Adherence to Immunosuppressive Medication Scale" (BAASIS ) questionnaire was used to assess self-reported adherence. The treating clinician scored patient's adherence and tacrolimus trough-concentration variability was calculated. In the analyses, the data from the different tools were dichotomized (adherent/nonadherent). The BAASIS overall response rate was over 80%. Intensive BAASIS assessment early after transplantation increased the chance of capturing a nonadherence event, but did not influence the 1-year adherence prevalence. The adherence tools generally captured different populations. Combining the tools, the nonadherence prevalence at 1 year was 38%. The different tools identified to a large degree different patients as nonadherent. Combining these tools is feasible for annual capture of adherence status.