Pragmatic clinical trials in the context of regulation of medicines.

The pragmatic clinical trial addresses scientific questions in a setting close to routine clinical practice and sometimes using routinely collected data. From a regulatory perspective, when evaluating a new medicine before approving marketing authorization, there will never be enough patients studied in all subgroups that may potentially be at higher risk for adverse outcomes, or sufficient patients to detect rare adverse events, or sufficient follow-up time to detect late adverse events that require long exposure times to develop. It may therefore be relevant that post-marketing trials sometimes have more pragmatic characteristics, if there is a need for further efficacy and safety information. A pragmatic study design may reflect a situation close to clinical practice, but may also have greater potential methodological concerns, e.g. regarding the validity and completeness of data when using routinely collected information from registries and health records, the handling of intercurrent events, and misclassification of outcomes. In a regulatory evaluation it is important to be able to isolate the effect of a specific product or substance, and to have a defined population that the results can be referred to. A study feature such as having a wide and permissive inclusion of patients might therefore actually hamper the utility of the results for regulatory purposes. Randomization in a registry-based setting addresses confounding that could otherwise complicate a corresponding non-interventional design, but not any other methodological issues. Attention to methodological basics can help generate reliable study results, and is more important than labelling studies as 'pragmatic'.