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Crowdsourcing a diagnosis? Exploring the accuracy of the size and type of group diagnosis: an experimental study
  1. Jonathan Sherbino1,
  2. Matt Sibbald1,
  3. Geoffrey Norman2,
  4. Andrew LoGiudice3,
  5. Amy Keuhl3,
  6. Mark Lee3,
  7. Sandra Monteiro1
  1. 1Department of Medicine, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada
  2. 2Department of Clinical Epidemiology and Biostatistics, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada
  3. 3Education Services, McMaster University Faculty of Health Sciences, Hamilton, Ontario, Canada
  1. Correspondence to Dr Jonathan Sherbino; sherbino{at}


Background The consultation process, where a clinician seeks an opinion from another clinician, is foundational in medicine. However, the effectiveness of group diagnosis has not been studied.

Objective To compare individual diagnosis to group diagnosis on two dimensions: group size (n=3 or 6) and group process (interactive or artificial groups).

Methodology Thirty-six internal or emergency medicine residents participated in the study. Initially, each resident worked through four written cases on their own, providing a primary diagnosis and a differential diagnosis. Next, participants formed into groups of three. Using a videoconferencing platform, they worked through four additional cases, collectively providing a single primary diagnosis and differential diagnosis. The process was repeated using a group of six with four new cases. Cases were all counterbalanced. Retrospectively, nominal (ie, artificial) groups were formed by aggregating individual participant data into subgroups of three and six and analytically computing scores. Presence of the correct diagnosis as primary diagnosis or included in the differential diagnosis, as well as the number of diagnoses mentioned, was calculated for all conditions. Means were compared using analysis of variance.

Results For both authentic and nominal groups, the diagnostic accuracy of group diagnosis was superior to individual for both the primary diagnosis and differential diagnosis. However, there was no improvement in diagnostic accuracy when comparing a group of three to a group of six. Interactive and nominal groups were equivalent; however, this may be an artefact of the method used to combine data.

Conclusions Group diagnosis improves diagnostic accuracy. However, a larger group is not necessarily superior to a smaller group. In this study, interactive group discussion does not result in improved diagnostic accuracy.

  • Decision making
  • Decision support, clinical
  • Medical education
  • Teams
  • Collaborative, breakthrough groups

Data availability statement

Data are available upon reasonable request.

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  • Contributors All authors were involved in the planning, conduct and reporting of this manuscript. JS is responsible for the overall content as guarantor.

  • Funding This study was funded by a Medical Education Research Grant from the Royal College of Physicians and Surgeons. The Royal College had no role in the study design; the collection, analysis and interpretation of data; the writing of the report or the decision to submit the article for publication. The researchers performed this study independently from the Royal College. All authors had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.