Editing Tip: 'Case' vs. 'Patient'

Clarifying the difference between ‘case’ and ‘patient’ in medical or clinical research

In another AJE Scholar article, we briefly outlined the difference between the clinical terms case and patient. In sum, a case is an occurrence of a clinical condition, and a patient is an individual with a clinical condition. Additionally, a case is presented or reported, whereas a patient is described. The distinction between the two terms may seem clear when composing a single sentence with a single instance. However, the choice of term becomes more perplexing when writing a more complex sentence or a paragraph.

Consistency within a sentence, if possible, is preferable for clarity. For example,

  • In our study, 10 cases (20%) out of 50 patients had evidence of tuberculosis co-infection. (inconsistent)
  • In our study, 10 cases (20%) out of 50 cases had evidence of tuberculosis co-infection. (consistent)
  • In our study, 10 patients (20%) out of 50 patients had evidence of tuberculosis co-infection. (consistent)

In contrast to the first sentence, which switches between the terms cases and patients, the second and third examples are both consistent. Additionally, these examples both present correct usage of the respective terms, as “had evidence of co-infection with tuberculosis” could apply to either the clinical condition or individuals with the clinical condition.

Consistency across consecutive sentences may also be clearer for your readers. For instance,  

  • Patients with a history of co-infection were excluded. The symptoms and treatment of these cases were recorded. (inconsistent)
  • Patients with a history of co-infection were excluded. The symptoms and treatment of these patients were recorded. (consistent)

Although patients and cases are being used correctly in the first example, for consistency, the second set of sentences is preferable. Note that using cases twice would be incorrect, as the phrase “with a history of co-infection” is more applicable to an individual with a clinical condition than to the occurence of a clinical condition.

This editing tip hopefully further clarifies the use of the terms case and patient in clinical writing. For more information on clinical writing, please refer to our downloadable resource on the topic. Please email us with any questions or comments on this tip. Thanks for your readership!

Special thanks to Sarah Conte for inspiring the examples above.

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