Abstract
Objective: We aim to assess which variables are associated with
recruitment failure of RCTs, leading to an extension of the study
period.. Design: Nationwide cohort study. Setting: A
cohort of RCTs supported by the trial centre of the Dutch Consortium of
Obstetrics and Gynaecology. Population: We included 83 RCTs
that recruited patients between March 1 st 2003 and
December 1 st 2023. Main outcome measures:
Primary outcome was recruitment target not achieved within six months
after the pre-planned recruitment period. Secondary outcomes were
recruitment target not achieved within an extension period of at least
twelve months and premature termination of the trial. Results:
In total, 46 of 83 RCTs (55%) did not achieve their targeted
recruitment within the pre-planned study period with a maximal extension
period of 6 months. The most relevant indicators for recruitment failure
in multivariable risk prediction modelling were presence of a
no-treatment arm, a compensation fee of less than 200 euros per included
patient, funding of less than 350.000 euros, while a preceding pilot
study lowered this risk. Conclusions: We identified that the
presence of a no-treatment arm, low funding and a low compensation fee
per included patient were the most relevant risk factors for recruitment
failure within the pre-planned period, while a preceding pilot study
lowered this risk. Awareness of these indicators is important when
designing future studies.