Bias and Loss to Follow-Up in Cardiovascular Randomized Trials: A Systematic Review [and Meta-Analysis].

Fong, Lucas Chun Wah; Ford, Thomas J; Da Costa, Bruno R.; Jüni, Peter; Berry, Colin (2020). Bias and Loss to Follow-Up in Cardiovascular Randomized Trials: A Systematic Review [and Meta-Analysis]. Journal of the American Heart Association, 9(14), e015361. American Heart Association 10.1161/JAHA.119.015361

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Background Loss to follow-up (LTFU) is common in randomized controlled trials. However, its potential impact on primary outcomes from cardiovascular randomized controlled trials is not known. Methods and Results We conducted a prospective systematic review (PROSPERO: CRD42019121959) for randomized controlled trials published in 8 leading journals over 5 years from January 2014 to December 2018. Extent, reporting, and handling of LTFU data were recorded, and the proportion of a trial's primary outcome results that lose statistical significance was calculated after making plausible assumptions for the intervention and control arms. These assumptions could drive differential treatment effects between the groups considering relative event incidence between LTFU participants and those included in the primary outcome. We identified 117 randomized controlled trials of which 91 (78%) trials reported LTFU, 23 (20%) reported no LTFU, and 3 (3%) trials did not report on whether LTFU occurred. The median percentage of study participants lost to follow-up was 2% (interquartile range, 0.33%-5.3%). Only 10 trials (9%) had a low cluster of risk factors for impairment in trial quality. The percentage of trials losing statistical significance varied from 2% when the relative event incidence for LTFU between the randomized groups was 1 for the intervention arm and 1.5 for the control arm to 16% when the relative event incidence was 3 for the intervention arm and 1 for the control arm. Conclusions Almost 1 in 6 (16%) cardiovascular randomized trials published in leading journals may have a change in the primary outcome if plausible assumptions are made about differential event rates of participants lost to follow up. There is scope for improvement arising from LTFU in randomized trials in cardiovascular medicine. Registration URL:; Unique identifier: CRD42019121959.

Item Type:

Journal Article (Original Article)


04 Faculty of Medicine > Medical Education > Institute of General Practice and Primary Care (BIHAM)

UniBE Contributor:

Da Costa, Bruno


600 Technology > 610 Medicine & health
300 Social sciences, sociology & anthropology > 360 Social problems & social services




American Heart Association




Andrea Flükiger-Flückiger

Date Deposited:

22 Jul 2020 21:51

Last Modified:

01 Oct 2020 20:21

Publisher DOI:


PubMed ID:


Uncontrolled Keywords:

bias loss to follow‐up outcome outcome and process assessment patient dropout randomized controlled trials relative risk




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