Proportion of published primary health care protocols with published results in subsequent papers was decreasing.

Objectives: We assessed the proportion of primary health care (PHC) randomized controlled trial (RCT) protocols published in peer-reviewed journals that published results in subsequent papers in peer-reviewed journals; and whether this proportion changed over time.

Study Design And Setting: We searched (last update June 2019) for RCTs published in peer-reviewed journals reporting primary outcome results for 620 protocols that were published up to 2014 and were retrieved in PubMed. We recorded the absolute number and the proportion of protocols with published results per year; and estimated whether the proportion changed over time.

Results: Of the 620 published protocols, 525 (85%) disseminated their results through a published RCT by June 2019. The number of published protocols was increasing over time especially after 2001. However, the proportion of protocols per year with published results in subsequent papers was decreasing over time after 2002. Specifically, the proportion ranged from 86% to 96% for protocols published until 2010 while for those published from 2011 onward ranged from 76% to 86%. Mean time from protocol to results publication was 39 months (95% CI 37, 41).

Conclusion: Almost one-sixth of PHC trial protocols published in peer-reviewed journals did not publish their results in subsequent papers.