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Modifiable factors influencing recruitment in clinical trials

Date and Location




Sunday 22 September 2013 - 10:30 - 12:00


Presenting author and contact person

Presenting author

Lotty Hooft

Contact person

Lotty Hooft
Abstract text
Background: Patient recruitment in clinical trials often takes longer than expected. Trials with slow recruitment are more costly and an insufficient sample size leads to indecisive conclusions. At present, determinants of slow recruitment that could help recruitment of patients both before and during clinical studies have not been systematically investigated. Objectives: To identify modifiable factors influencing recruitment in clinical trials. Methods: We included all 1130 trials registered in the Netherlands Trial Register with an expected date of completion between 2005 and 2010. Through a questionnaire sent to the principle investigators we identified characteristics of the principal investigator and research group, hospital organization, trial organization and design. We used logistic regression analysis to assess which characteristics were associated with (un)successful recruitment. Results: Of 392 trials (35%) questionnaires were completed. For these trials 232.707 persons were to be recruited. Half of the trials did not achieve their original recruitment target (i.e. 80% of the targeted number of patients within the planned time). Although 42% of the trials were extended for ≥6 months, when closing recruitment 46% still had recruited fewer patients than originally intended. Factors associated with unsuccessful recruitment were: lack of clear responsibilities for recruitment, trial coordinator not PhD, multicenter trial (especially >10 centres). Factors associated with successful recruitment were: newsletter and presentation at start for recruiters, pocket cards, and email at start of the trial. Conclusions: Investigators overestimate recruitment success in almost half of the trials. Although we identified factors associated with recruitment, we are yet unable to make a general checklist for improving recruitment. A possible limitation of this study is the risk for selective responses and unmeasured confounders. Nevertheless, trialists and funders should be aware of potential recruitment barriers and incentives at study design as well as during the study.