Javier Bracchiglione publishes important study on clinical trials
18/05/2025
Dr Javier Bracchiglione, senior researcher at the Centre for Health Research (CIESAL) at the Universidad de Valparaíso, has co-authored a major study which has recently been published in the Journal of Clinical Epidemiology, one of the most influential journals in the field of clinical research. The article, entitled ‘Empirical evidence of observer bias in randomised clinical trials: updated and expanded analysis of trials with both blinded and non-blinded outcome assessors’, was led by the Centre for Evidence-Based Medicine Odense (CEBMO), part of Cochrane Denmark.
The study addresses the impact of blinding – also known as masking – in randomised clinical trials, a fundamental practice to minimise bias in outcome measurement. Blinding entails that participants, healthcare professionals and/or researchers do not know which treatment has been assigned to which individual, with the aim of preventing such information from influencing the assessment of study outcomes.
The research focused on the role of the ‘event adjudicator’, i.e. the person in charge of determining whether an outcome occurred. By analysing trials in which the same outcome was assessed by both a blinded and unblinded adjudicator, the authors found that unblinded adjudicators tended to overestimate the effect of the intervention by 29%. This bias was even greater in industry-funded studies or non-pharmacological interventions.
The research team comprised Dr Josefina Salazar, doctoral candidate at CEBMO; Dr Helene Moustgaard, lead author of the influential MetaBLIND study; Dr Javier Bracchiglione from CIESAL; and Dr Asbjørn Hróbjartsson, director of CEBMO and Cochrane Denmark, renowned for his contributions to clinical research methodology and evidence synthesis.
Dr. Bracchiglione’s participation in this work stemmed from his international internship at CEBMO in 2023, which enabled him to strengthen academic ties and promote international collaboration.
CIESAL would like to congratulate Dr. Bracchiglione for this significant contribution, which reinforces our line of research in Clinical Epidemiology and Evidence-Based Medicine and contributes to methodological advances in the design and evaluation of clinical trials at a global level.
Dr Javier Bracchiglione, senior researcher at the Centre for Health Research (CIESAL) at the Universidad de Valparaíso, has co-authored a major study which has recently been published in the Journal of Clinical Epidemiology, one of the most influential journals in the field of clinical research. The article, entitled ‘Empirical evidence of observer bias in randomised clinical trials: updated and expanded analysis of trials with both blinded and non-blinded outcome assessors’, was led by the Centre for Evidence-Based Medicine Odense (CEBMO), part of Cochrane Denmark.
The study addresses the impact of blinding – also known as masking – in randomised clinical trials, a fundamental practice to minimise bias in outcome measurement. Blinding entails that participants, healthcare professionals and/or researchers do not know which treatment has been assigned to which individual, with the aim of preventing such information from influencing the assessment of study outcomes.
The research focused on the role of the ‘event adjudicator’, i.e. the person in charge of determining whether an outcome occurred. By analysing trials in which the same outcome was assessed by both a blinded and unblinded adjudicator, the authors found that unblinded adjudicators tended to overestimate the effect of the intervention by 29%. This bias was even greater in industry-funded studies or non-pharmacological interventions.
The research team comprised Dr Josefina Salazar, doctoral candidate at CEBMO; Dr Helene Moustgaard, lead author of the influential MetaBLIND study; Dr Javier Bracchiglione from CIESAL; and Dr Asbjørn Hróbjartsson, director of CEBMO and Cochrane Denmark, renowned for his contributions to clinical research methodology and evidence synthesis.
Dr. Bracchiglione’s participation in this work stemmed from his international internship at CEBMO in 2023, which enabled him to strengthen academic ties and promote international collaboration.
CIESAL would like to congratulate Dr. Bracchiglione for this significant contribution, which reinforces our line of research in Clinical Epidemiology and Evidence-Based Medicine and contributes to methodological advances in the design and evaluation of clinical trials at a global level.