Clinical Questions: PICO and PEO Research

When you’re beginning the clinical research process, one of your first decisions will be around framing your clinical question. That, in turn, will depend on if your research is quantitative, or based on numerical data, or qualitative research based on non-numerical data. A PICO clinical question is tied to quantitative data, whereas a PEO question relates to qualitative data.

Let’s take a look at both of these clinical question formats.

What is a PICO Question?

As mentioned above, a PICO research question is used when quantitative data is involved. PICO stands for:

• P – Population, Patient and/or Problem: How do you describe the patients, people or the problem that you’re looking at?
• I – Intervention: What are you considering for an intervention, exposure or factor?
• C – Comparison: Do you have something to compare to the intervention, exposure or factor that you’re considering?
• O – Outcome: What are you hoping to measure, improve, affect or accomplish?

So, essentially, your PICO question will answer the above aspects. This type of clinical question is most often used when the research is investigating evidence-based medicine or other interventions. However, the PICO question format can also be used for non-clinical settings, such as psychological interventions for school-age children, and how they relate to academic achievement.

How to Write a PICO Question

It can sometimes be a challenge to write PICO Questions, as they can be very complex. Since we are looking at evidence-based conclusions, great thought has to be put into formulating a PICO research question. Once the question has been written and clarified, it can help the researcher determine what type of study model will work best to answer the question. So, in a very real way, asking the question properly helps you select what type of study you’ll be conducting.

Fortunately, once you are comfortable with the elements of a PICO question, it almost becomes a plug and play model. For example, if you are looking at questions around prognosis, you might structure your PICO question like this:

Would ________________ (I) affect or influence _________________________ (O) with patients or people who have ___________________________________________________ (P) compared to __________________________(C)?

Another example of a PICO research question might include an inquiry into prevention:

With ___________________ (P) does the practice or use of ________________________ (I) reduce or prevent risk of __________________________(O), compared with __________________________(C)?

What is a PEO Question?

A PEO research question focuses on non-numerical data, or qualitative research. Here, relationships and associations are explored. For example, a PEO question can try to explore whether there is a correlation between taking baby aspirin and a lowered risk of heart attacks.

PEO stands for:

• Population: Who are you studying? Infants? Males who are between the ages of 55 and 60? Adolescent females?
• Exposure: What is your population exposed to? Baby aspirin? Soy supplements? Peanuts?
• Outcome: What is the result of the exposure on your population? Lowered risk for heart attacks? Food allergies? Increased menstrual cramps?

How to Write a PEO Question

Writing a PEO question isn’t generally as complex as writing a PICO question, since you’re only looking at what population, what they’re exposed to, and what your expected outcome is. For example, if you’re looking at food allergies in infants, your PEO question might look like this:

In infants between the age of 6 to 9 months (P), is there an association between exposure to micro-doses of common food allergens (E) and reduced childhood food allergies? (O)

Similar questions can be explored this way:

In or with ___________________ (P), will ________________________(E) result in _________________________ (O)?

Using PICO and PEO Research Questions for Literature Reviews of Searching

Just as you might utilize PICO and PEO question formatting for designing your research, you can also tap into their formats when you’re looking for previous studies on your topic of interest. For example, if you are looking for information on dietary interventions and type 2 diabetes reversal, you can use keywords related to the formulation of a research question:

P: Individuals with type 2 diabetes
E: Mediterranean Diet
O: Reversal of type 2 diabetes

To find research related to the above question, you would pull out keywords, like:

“type 2 diabetes,” “reversal” and “Mediterranean Diet”

Clinical Question Formats

There are a wide variety of clinical question formats, in addition to PICO and PEO. These can include PICO(T), which adds a “time-frame” ingredient, and (P)PICO if your population is more complex, like white males, age 50-55.

The bottom line is that an effective clinical research question needs to be relevant to the patient or problem, and worded in a way that it’s easy for those looking for your research to find it. If you’re designing a research project, starting with an effective and well-written clinical research question is a critical first step.

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