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What is a case series?

A case series is a descriptive study that presents detailed information about a group of patients who share a similar diagnosis, treatment, exposure or clinical presentation. Unlike a case report, which focuses on a single patient, a case series includes multiple cases, allowing patterns, similarities and differences to be explored across individuals.


Case series are often used when clinicians observe an unusual cluster of cases, a novel treatment approach, a new complication or a pattern that may indicate an emerging clinical issue. They serve as an important foundation for generating hypotheses and informing further research.


What case series typically include

Case series generally describe:

  • A group of patients with a shared condition, treatment or presentation
  • Clinical characteristics such as symptoms, diagnosis and management
  • Follow-up information across the included patients
  • Patterns or trends observed within the group
  • Insights that may suggest new hypotheses or clinical considerations


Because these studies involve more than one patient, they offer richer comparative detail than case reports.


Key features of case series

  • Descriptive: Summarises characteristics and management of multiple cases
  • Observational: Involves no intervention or comparison groups
  • Pattern-focused: Identifies similarities or emerging trends across cases
  • Contextual: Provides narrative and clinical detail
  • Foundation for research: Helps generate hypotheses for future studies


Benefits of case series

  • Provides valuable clinical insight across multiple patients
  • Allows comparison of patterns and variability within the group
  • Requires fewer resources than large observational or experimental studies
  • Supports hypothesis generation for future research
  • Useful for documenting early evidence of new or rare conditions
  • Helps clinicians share lessons that may improve practice


Limitations of case series

  • Generalisability is limited because the sample is small and not randomly selected
  • No control group is included, preventing comparison or causal inference
  • Subjectivity may influence how cases are selected or described
  • Difficult to determine whether observed patterns reflect true associations
  • Publication bias may favour unusual or dramatic case clusters


When should you use a case series?

Use a case series when you want to:

  • Describe a group of patients with a similar or unusual presentation
  • Document early clinical experiences with a new treatment or technique
  • Highlight emerging trends that may require further investigation
  • Explore variability and consistency across individual cases
  • Generate research questions for future observational or experimental studies
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