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Systematic and Systematic-like Reviews

What is a Critically-Appraised Topic (CAT)?

A Critically Appraised Topic (CAT) is a short summary of the best available evidence on a focused question.  It is a shorter, less rigorous type of systematic review, providing an assessment of what is known about an intervention or issue by searching and appraising relevant studies.

Because it is faster than a full systematic review, a CAT does have limitations in terms of comprehensiveness and so is much more prone to selection bias than a systematic review or a rapid review.  

Parts of a CAT

As with any systematic-like review, you should follow a certain methodology: 

  1. Define a clear, concise and focused question – use a search framework such as PICO to help you with this.
  2. Develop a search strategy – identify search terms, work out how to combine them and select a limited number of appropriate databases.
  3. Identify the relevant studies that help answer your question.
  4. Critically appraise the located evidence – describe and appraise the included studies. (Often the appraisal is limited to the methodological appropriateness of each study).
  5. Summarise your findings – what’s the “bottom line” suggested by the evidence?  

Further information

Examples from the fields of veterinary science, dermatology, business management and physiotherapy:

  • Brennan, M. L., Arlt, S. P., Belshaw, Z., Buckley, L., Corah, L., Doit, H., Fajt, V. R., Grindlay, D. J. C., Moberly, H. K., Morrow, L. D., Stavisky, J., & White, C. (2020). Critically Appraised Topics (CATs) in veterinary medicine: Applying evidence in clinical practice. Frontiers in Veterinary Science, 7, 314-314. https://doi.org/10.3389/fvets.2020.00314
  • Callander, J., Anstey, A. V., Ingram, J. R., Limpens, J., Flohr, C., & Spuls, P. I. (2017). How to write a Critically Appraised Topic: Evidence to underpin routine clinical practice. British Journal of Dermatology, 177(4), 1007-1013. https://doi.org/10.1111/bjd.15873
  • Physiopedia (2020). Critically appraised topics. https://www.physio-pedia.com/Critically_Appraised_Topics

Examples of a published CAT:

  • Olivry, T., Mueller, R.S. & Prelaud, P. (2015). Critically appraised topic on adverse food reactions of companion animals (1): duration of elimination diets. BMC Veterinary Research, 11(3). https://doi.org/10.1186/s12917-015-0541-3

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