Why we are building the Catalogue of Bias


Bias enters health studies at all stages and often influences the magnitude and direction of results. To obtain the least biased information, researchers must acknowledge the potential presence of biases and take steps to avoid and minimise their effects. Equally, in assessing the results of studies we must be aware of the different types of biases, their potential impact and how this affects interpretation and use of evidence in health care decision making.

To better understand the persistent presence, diversity and impact of biases, we are compiling a Catalogue of Biases, stemming from original work by David Sackett. The entries are a work in progress and describe a wide range of biases –  outlining their potential impact in research studies.

Dave’s methods could be unorthodox but were highly effective

Sackett recognised the importance of bias in research. His 1979 paper “Bias in Analytic Research”, published in the Journal of Chronic Disease, reported the first draft of a ‘catalog of biases which may distort the design, execution, analysis and interpretation of research.’[1]  Sackett catalogued 35 biases that arise in sampling and measurement, in the context of clinical trials, and listed 56 biases potentially affecting case-control and cohort studies.

He proposed the continued development of an annotated catalogue of bias as a priority for research.

Scan of a paper

Sackett DL. Bias in Analytical Research. Chron Dis 1979;32:51-63.

stating that each citation should include a useful definition, a referenced example illustrating the magnitude and direction of its effects, and a description of the appropriate preventive measures if any.

The Catalogue of bias Collaboration is, therefore, taking forward the task of creating a Catalogue of Biases in memory of Dave’s work. We welcome further contributions and collaborations in order to continually refine and update this resource.

Catalogue of Biases Collaboration: 

The collaboration meets every 6 months to develop and refine the contents of the catalogue and in between work on updating content.

Editors: Nunan D, Spencer EA, Badenoch D, Heneghan C.

Collaboration authors: Aronson JKA 1, Badenoch D 2, Banerjee A 3, Bankhead C 1, Brassey JA 4, Davis R 1, Heneghan C 1, Mahtani K 1, Nunan D 1,  O’Sullivan J 1, Pluddemann A 1.

  1. CEBM
  2. Minervation
  3. UCL
  4. TRIP