Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Background: Recruitment targets to randomized controlled trials (RCTs) are often not met. Many interventions are used to improve recruitment but there is little empirical evidence on whether these approaches work. Objective: To examine whether changes to the design and conduct of a primary care-based RCT were associated with changes in patient recruitment. Methods: An observational time series analysis of recruitment to a primary care-based multi-centre RCT of aspirin versus warfarin for stroke prevention, which involved 330 practices. Several changes to the trial protocol and procedures were made over the 4 years of patient recruitment. For each quarter throughout the recruitment period, the recruitment rate per 1000 total population in active practices was calculated. Results: The recruitment target of 930 patients was exceeded. Fluctuations in recruitment rate occurred during the recruitment period. Following protocol changes aimed to reduce clinical workload, there was a significant increase in recruitment during the final 6 months of the study, during a period when there was not a similarly large increase in the total population available. Conclusions: These findings suggest that the conduct of a trial is an important consideration if studies are to recruit successfully. Expanding the number of centres may not be the most effective way to improve recruitment. © The Author 2010. Published by Oxford University Press. All rights reserved.

Original publication




Journal article


Family Practice

Publication Date





691 - 697