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Which study type is that? A guide to study types

Study and experiment types for Health Sciences and Medicine

Case series


A case series is a collection of case reports involving multiple patients who have received similar treatment or have similar characteristics. These patients are studied over time and usually include detailed information including demographics, treatment received and outcomes. There is no comparison group in this type of study and it can be vulnerable to selection bias but can be useful to identify new trends, diseases or an understanding of the course of a condition.

case series

Useful for addresing:

Observational questions, Therapy questions, Prognosis questions

Strengths and limitations

 

Strengths

  • High external validity
  • No interference in treatment decision process
  • Wide range of patients
  • Inexpensive
  • Study conduct takes little time

Limitations

  • Lack of comparison group
  • Data collection often incomplete
  • Susceptible to bias
  • Selection bias
  • Measurement bias

Kooistra, B., Dijkman, B., Einhorn, T. A., & Bhandari, M. (2009). How to design a good case series. JBJS, 91(Supplement_3), 21-26.

Further reading and resources

  • Agha, R. A., Fowler, A. J., Rajmohan, S., Barai, I., Orgill, D. P., Afifi, R., ... & Rosin, D. (2016). Preferred reporting of case series in surgery; the PROCESS guidelines. International journal of surgery, 36, 319-323. Full Text
     
  • Dekkers, O. M., Egger, M., Altman, D. G., & Vandenbroucke, J. P. (2012). Distinguishing case series from cohort studies. Annals of internal medicine, 156(1_Part_1), 37-40. Full Text
     
  • Ganesan, P. (2022). How to write case reports and case series. International Journal of Advanced Medical and Health Research, 9(1), 55-58. Full Text
     
  • Joanna Briggs Institute (JBI). (2020) Critical appraisal checklist for case series. https://jbi.global/sites/default/files/2020-07/Checklist_for_Case_Series_0.pdf  Full Text
     
  • Kooistra, B., Dijkman, B., Einhorn, T. A., & Bhandari, M. (2009). How to design a good case series. JBJS, 91(Supplement_3), 21-26. Full Text

Example

Boudabous, S., Bouacida, I., Yahia, M. B. H., Zribi, H., & Marghli, A. (2025). Surgical management of infected emphysema bulla: A case series. International journal of surgery case reports, 126, 110718. Full Text

 

 


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