Main findings
A usefulness tool was developed with eight criteria combining 13 items identified through literature searches and consensus. Among 350 RCTs in PTB, many usefulness features were not met, with one tenth of trials meeting half of the items evaluated. Exploring the change in usefulness over time, most usefulness transparency features started to appear after the year 2000 and became more prominent after 2010. We found no substantial change in information gain, except for higher impact journals, which increased their information gain by reporting more complete power calculations, but in return more surrogate and composite outcomes as primary outcome were used. There was a remarkable absence of patient centeredness and value for money, and a very low percentage of pragmatic trial designs.