Faculty of Health and Medical Sciences

Apply the evidence


A set of scales for weighing things

Even if research evidence has internal validity, it often applies to the ‘ideal’ patient who has been selected for a clinical trial, and estimates an ‘average’ benefit for that patient. However, to decide whether you can apply that evidence to your patient, you must consider:

  • that individual’s characteristics, preferences, values
  • the environment in which you practice
  • the practitioner’s expertise and familiarity with an intervention

You are now looking at external validity.

Before extrapolating beyond the trial, ask yourself these questions:

  1. Are the results clinically important?
  2. Do the results apply to my patient?
  3. What are my patients’ values and preferences?
  4. Can this practice be implemented in this healthcare setting?
  5. How can I help my patient make a decision?