The relevance of practice misalignments to trials in transfusion medicine: Practice misalignments in trials of existing therapies

Practice misalignments can occur in any clinical trial investigating a pre-existing therapy that is typically adjusted based on clinical characteristics outside of the trial setting. To eliminate the heterogeneity in clinical practice, recent trials investigating titrated therapies have randomized patients to fixed-dose regimens without including a routine care control group receiving titrated therapy. In these trials, the normal relationships between clinically important characteristics and therapy titration are disrupted. Within each arm of the trial, randomization creates subgroups of patients receiving levels of therapy inconsistent with current practices outside of the trial. These practice misalignments may have outcomes worse than routine care and may compromise patient safety. In addition, comparisons of trial arms with practice misalignments have limited interpretability and generalizability. In this review, we use examples from the literature to discuss how practice misalignments can impact the safety, results and conclusions of clinical trials. In addition, we discuss methods to characterize relationships between therapy titration and clinical characteristics and trial design strategies that may minimize practice misalignments.