Evidence to support clinical decision making must be based on safety data that have been captured, analysed, and interpreted in a robust and reliable way. Randomised real-world evidence (RRWE) studies provide the opportunity to evaluate the use of medicines in patients and settings representative of routine clinical practice. However, elements that underpin the design of RRWE studies can have a significant impact upon the analysis, interpretation, and implications of safety data.In this narrative review, we use data from the Salford Lung Study; two prospective, 12-month, open-label, parallel-group, phase III randomised controlled trials conducted in primary care in the UK; to highlight the importance of capturing treatment modifications when attempting to evaluate safety events according to actual treatment exposure.We demonstrate that analysing safety data by actual treatment received (i.e. accounting for the treatment modifications that occur routinely in the primary care setting) provides additional insight beyond analysing according to randomised treatment strategy only.It is therefore proposed that understanding of safety data from RRWE trials can be optimised by analysing both by randomised group and by actual treatment received.

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The use of real-world evidence (RWE) studies, including pragmatic randomised controlled trials (RCTs; randomised RWE studies), to aid the development of treatment guidelines, is gradually becoming a mainstay within clinical practice. RWE is an integral part of patient-driven decision-making and offers important value to add complimentary evidence to traditional RCTs; these provide a more well-rounded view of the benefits to patient-reported outcomes and improve the external validity of a given treatment versus findings from traditional RCTs alone. Discussions in recent scientific workshops explored the importance of pragmatic RCTs in optimising guideline development and patient care in chronic obstructive pulmonary disease (COPD) and asthma. The Salford Lung Study in patients with COPD (NCT01551758) and asthma (NCT01706198) were the world’s first prelicence pragmatic RCTs that compared novel investigational treatments with existing COPD and asthma treatments and, more recently (2021), RWE studies have been used by the American Thoracic Society and the US Food and Drug Administration to support the approval of an immunosuppressant drug in patients receiving lung transplants. This highlights the importance of RWE data in supporting clinical guideline development and emphasises the advantages for the use of pragmatic RCTs in guiding clinical practice.