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Which study type is that? A guide to study types

Study and experiment types for Health Sciences and Medicine

Non-randomised trial


A clinical trial in which the participants are not assigned by chance to different treatment groups. Participants may choose which group they want to be in, or they may be assigned to the groups by the researchers (National Cancer Institute n.d.)

 Infographic titled "Non-randomised trial" showing two groups assigned to treatments without randomisation, with a bias icon indicating potential measurement bias.

Disadvantages

The lack of randomisation has the potential to introduce selection bias as the groups may differ in ways that affect the outcome. 

Further reading and resources

  • MacDougall, M. (Ed.). (2023). A Medical Educator's Guide to Thinking Critically about Randomised Controlled Trials: Deconstructing the" gold Standard". Springer. Catalogue Link
     
  • National Cancer Institute. (n.d.). Nonrandomised clinical trial. National Cancer Institute at the National Institutes of Health. Retrieved December 2, 2024, from https://www.cancer.gov/publications/dictionaries/cancer-terms/def/nonrandomized-clinical-trial Link
     
  • Sterne, J. A., Hernán, M. A., McAleenan, A., Reeves, B. C., & Higgins, J. P. (2019). Assessing risk of bias in a non‐randomized study. Cochrane handbook for systematic reviews of interventions, 621-641. Catalogue Link

Example

Kalinsky, K., Hong, F., McCourt, C. K., Sachdev, J. C., Mitchell, E. P., Zwiebel, J. A., Doyle, L. A., McShane, L. M., Li, S., Gray, R. J., Rubinstein, L. V., Patton, D., Williams, P. M., Hamilton, S. R., Conley, B. A., O'Dwyer, P. J., Harris, L. N., Arteaga, C. L., Chen, A. P., & Flaherty, K. T. (2021). Effect of Capivasertib in Patients With an AKT1 E17K-Mutated Tumor: NCI-MATCH Subprotocol EAY131-Y Nonrandomized Trial. JAMA oncology, 7(2), 271–278. https://doi.org/10.1001/jamaoncol.2020.6741 Full Text


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