Interpretation
Previous empirical evaluations have focused on one or a few aspects of some of the items that were considered in our eight usefulness criteria. For example, there are several empirical studies examining the conduct of systematic reviews preceding a trial (17,18), the use of power calculations (19), pragmatism (12) and use of transparency practices such as protocol and data sharing, registration, disclosures of funding and conflicts of interest.(20,21) However, our evaluation provides a composite assessment across multiple domains in a scale that is unprecedented and offers a wider view. For PTB research there is no prior empirical evaluation of most of these usefulness features, but there is definitely awareness of the problems arising from lack of these features.(22) One study for example evaluated the effect of pre-registration and its impact on reducing selective outcome reporting in trials and meta-analysis evaluating progesterone for PTB prevention. This study identified 93 RCTs and 29 systematic reviews and found a remarkable difference in the reported effectiveness of progesterone when evaluating the subset of trials reporting a pre-registered primary outcome only (n=22), compared to the totality of trials and reviews.(23) This example highlights the importance of addressing preregistration, protocol and data availability. Sadly, these transparency features still represent a minority of the 138 trials published between 2010 to 2019 assessed in the current project.