Main findings
In this nationwide cohort study, 46 of 83 included RCTs (55%) did not
achieve their recruitment target within the pre-planned study period
with a maximal extension period of six months. RCTs that had a
no-treatment arm, low funding and low financial compensation per
included patient were at risk to experience this type of recruitment
failure, while a preceding pilot study lowered this risk. Upon extension
of the pre-planned study period from six to twelve months, 41 RCTs
(49%) still did not achieve the pre-planned recruitment target.
Nineteen RCTs (23%) were stopped prematurely because of recruitment
issues.