Reasons for Disparity in Statin Adherence Rates between Clinical Trials and Real World Observations. A Review.

With statins, the reported rate of adverse events differs widely between randomized clinical trials (RCTs) and observations in clinical practice, the rates being 1-2% in RCTs versus 10-20% in the so-called real world. One possible explanation is the claim that RCTs mostly use a run-in period with a statin. This would exclude intolerant patients from being included into RCTs and therefore favor a bias towards lower rates of intolerance.We here review data from RCTs with more than 1000 participants with and without a run-in period, which were included in the Cholesterol Treatment Trialists collaboration (CTTC). Two major conclusions arise: 1) The majority of RCTs did not have a test dose of a statin in the run-in phase. 2) A test dose in the run-in phase was not associated with a significantly improved adherence rate within that trial when compared to trials without a test dose. Taken together, the RCTs of statins reviewed here do not suggest a bias towards an artificially higher adherence rate because of a run-in period with a test dose of the statin.Other possible explanations for the apparent disparity between RCTs and real world observations are also included in this review albeit mostly not supported by scientific data.