Reporting of pre-enrolment screening with randomized clinical trials: A small item that could impact a big difference

Randomized controlled trials (RCTs), when conducted using ethical and transparent methods, become the ultimate standard for producing evidence-based knowledge in the field of medical research. We sought to determine the proportion of RCTs in which the number of screened patients is reported, and also to ascertain what predicted efficient screening (i.e., a high number of screened participants being enrolled).

Thirty-five RCTs from the Journals Clinical Infectious Diseases and The Lancet Infectious Diseases were reviewed from the time period of January 2012 to July 2013 using standardised criteria.

From the 35 RCTs, 9 of 35 (26%) did not report the number of patients screened prior to recruitment. From the 26 studies that reported this screening figure, 10,215 (47%; range: 2-98%) of the screened participants (21,862) were subsequently enrolled. About 18.3% of those screened and not enrolled, met inclusion and exclusion criteria yet did not wish to participate in an RCT. Studies performed in developed countries and pediatric populations were more likely to have low rates of enrolment compared with the screened population although there was no statistical significance to these associations (P = 0.2 for both variables).

Many reports of RCTs do not report screening figures, even though these add useful information about the feasibility of future trials.