Adherence and renal biopsy feasibility in the Renin Angiotensin-System Study (RASS) primary prevention diabetes trial

Aims: Enhancing adherence in research trials is fundamental to the proper testing of treatment hypotheses. Methods: Regimen and follow-up adherence as well as factors associated with adherence in the Renin Angiotensin-System Study (RASS) diabetic nephropathy primary prevention trial were evaluated. Adherence to medication (i.e., pill count), follow-up visits, and follow-up renal biopsies was evaluated. Results: 89.8% of subjects completed the second renal biopsy. 96% of follow-up visits were attended within prescribed time windows. Mean medication adherence was 85.6%. Subgroup analyses revealed greater declines in the least adherent participants over time. Factors associated with greater adherence levels included older age, type 1 diabetes (TIDM) duration, lower HbA_1c and blood pressure, GFR, ethnicity, and participants', principal investigators' (PI), and trial coordinators' (TC) baseline predictions of adherence. Conclusions: T1DM patients without nephropathy were willing to take experimental medications and undergo repeat renal biopsies. Although overall adherence was excellent, patterns of adherence varied among participants, suggesting the need to better track adherence and to develop customized and targeted approaches for promoting adherence to clinical research regimens. Staff subjective predictions of adherence were imprecise, supporting need for further development of adherence predictors.