Considerations in the evaluation and determination of minimal risk in pragmatic clinical trials

The classification system for categorizing the riskiness of a clinical trial is largely defined by the body of federal regulations known as the Common Rule (45 CFR 46, Subpart A) and by regulations governing the US Food and Drug Administration (FDA) codified in 21 CFR 50. This rule is applied according to the interpretation of institutional review boards (IRBs) charged with overseeing the research. If a clinical trial is determined by an IRB to constitute “minimal risk,” there are important practical implications: the IRB may allow waiver or alteration of the informed consent process; the study may be carried out in certain vulnerable populations; or the study may be reviewed by IRBs using an expedited process. However, it is unclear how the risk levels of pragmatic clinical trials (PCTs) should be assessed. Such trials typically compare existing, widely used medical therapies or interventions in the setting of routine clinical practice. Some of the therapies may be considered risky of themselves but the study comparing them may or may not add to that pre-existing level of risk. In this paper, we examine current research regulations and common interpretations of those regulations and suggest that current interpretation and application of regulations governing minimal-risk classification are marked by a high degree of variability and confusion, which in turn may ultimately harm patients by delaying or hindering potentially beneficial research. We advocate for a clear differentiation between the risks associated with a given therapy and the incremental risk incurred during research evaluating those therapies as a basic principle for evaluating the risk of a clinical study. We then examine two studies that incorporate aspects of PCTs and consider how various factors including patient perspectives, clinical equipoise, practice variation, and research methods such as cluster randomization contribute to current and evolving concepts of minimal risk, and how this understanding in turn affects the design and conduct of PCTs.