As opposed to an "explanatory" or "mechanistic" randomized controlled trial (RCT), which seeks to examine the effect of an intervention under tightly controlled circumstances, "pragmatic" or "naturalistic" trials study interventions and their outcomes when used in more real-world, generalizable settings. One example of such a study might include the use of registry data to examine interventions and outcomes as they occur in the "real world" of patient care. However, there are currently few standards for identifying, reporting, and discussing the results of such "pragmatic RCTs." A new paper by Nicholls and colleagues aims to provide an overview of the current landscape of this methodological genre.
The authors searched for and synthesized 4,337 trials using keywords such as "pragmatic," "real world," "registry based," and "comparative effectiveness" to better map an understanding of how pragmatic trials are presented in the RCT literature. Overall, only about 22% (964) of these trials were identified as "pragmatic" RCTs in the title, abstract, or full text; about half of these (55%) used this term in the title or abstract, while the remaining 45% described the work as a pragmatic trial only in the full text.
About 78.1% (3,368) of the trials indicated that they were registered. However, only about 6% were indexed in PubMed as a pragmatic trial, and only 0.5% were labeled with the MeSH topic of Pragmatic Clinical Trial. The target enrollment of pragmatic trials was a median of 440 participants within an interquartile range (IQR) of 244 to 1,200; the actual achieved accrual was 414 (IQR: 216 - 1,147). The largest trial included 933,789 participants; the smallest enrolled 60.
Overall, pragmatic trials were more likely to be centered in North America and Europe and to be funded by non-industry sources. Behavioral, rather than drug or device-based, interventions were most common in these trials. Not infrequently, the trials were mislabeled or contained erroneous data in their registration information. The fact that only about half of the sample were clearly labeled as "pragmatic" may mean that these trials may go undetected with less sensitive search mechanisms than the authors used.
Authors of pragmatic trials can improve the quality of the field by clearly labelling their work as such and by registering their trials and ensuring that registered data are accurate and up-to-date. The authors also suggest that taking a broader view of what constitutes a "pragmatic RCT" also generates questions regarding proper ethical standards when research is conducted on a large scale with multiple lines of responsibility. Finally, the mechanisms used to obtain consent in these trials should be further examined in light of the finding that many pragmatic trials fail to achieve goals set for participant enrollment.
Manuscript available from publisher's web site here.
Nicholls SG, Carroll K, Hey SP, et al. (2021). A review of pragmatic trials found a high degree of diversity in design and scope, deficiencies in reporting and trial registry data, and poor indexing. J Clin Epidemiol (ahead of print).