Unreported exclusion and sampling bias in interpretation of randomized controlled trials in patients with STEMI

Research output: Contribution to journalArticle


Aims: To assess the impact of sampling bias due to reported as well as unreported exclusion of the target population in a multi-center randomized controlled trial (RCT)of ST-elevation myocardial infarction (STEMI). Methods and Results: We compared clinical characteristics and mortality between participants in the DANAMI-3 trial to contemporary non-participants with STEMI using unselected registries. A total of 179 DANAMI-3 participants (8%)and 617 contemporary non-participants (22%)had died (Log-Rank: P < 0.001)after a median follow-up of 1333 days (range: 1–2021 days). In an unadjusted Cox regression model all groups of non-participants had a higher hazard ratio to predict mortality compared to participants: eligible excluded (n = 144)(hazard ratio: 3.41 (95% CI: (2.69–4.32)), ineligible excluded (n = 472)(hazard ratio: 3.42 (95% CI: (2.44–4.80), eligible non-screened (n = 154)(hazard ratio: 3.37 (95% CI: (2.36–4.82)), ineligible non-screened (n = 154)(hazard ratio: 6.48 (95% CI: (4.77–8.80). Conclusion: Sampling bias had occurred due to both reported and unreported exclusion of eligible patients and the difference in mortality between participants and non-participants could not be explained only by the trial exclusion criteria. Thus, screening logs may not be suited to address the risks of sampling bias.


  • Peter Nørkjær Laursen
  • Lene Holmvang
  • Jacob Lønborg
  • Lars Køber
  • Dan E. Høfsten
  • Steffen Helqvist
  • Peter Clemmensen
  • Henning Kelbæk
  • Erik Jørgensen
  • Jens Flensted Lassen
  • Frants Pedersen
  • Thomas Høi-Hansen
  • Bent Raungaard
  • Christian Juhl Terkelsen
  • Lisette Okkels Jensen
  • Golnaz Sadjadieh
  • Thomas Engstrøm
External organisations
  • Copenhagen University Hospital
  • University Medical Center Hamburg-Eppendorf
  • Nykøbing Falster Hospital
  • University of Southern Denmark
  • Gentofte Hospital
  • Aalborg University
  • Aarhus University Hospital
  • Odense University Hospital
  • Zealand University Hospital
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Cardiac and Cardiovascular Systems


  • External validity, Randomized controlled trials, Sampling bias, Screening logs, ST-elevation myocardial infarction
Original languageEnglish
Pages (from-to)1-5
JournalInternational Journal of Cardiology
Early online date2019
Publication statusPublished - 2019
Publication categoryResearch