Impact of study design on recruitment of patients to a primary care trial: an observational time series analysis of the Birmingham Atrial Fibrillation Treatment of the Aged (BAFTA) Study

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Colleges, School and Institutes


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.


Original languageEnglish
JournalFamily Practice
Publication statusPublished - 7 Jul 2010


  • Patient recruitment, trial design, RCT