Skip to Main Content

2021 - PHCY 504 - Primary and Secondary Literature Tutorial: PICO & Clinical Questions

Created by Health Science Librarians

PICO & Clinical Questions - Sample Case

As we go through this module, we’re going to keep coming back to Ned, our example case, and we’re going to use this case to talk about how we would develop a well-built clinical question and then execute a search based on that question.  

So, let’s get to the facts of Ned’s case.  

Ned has been taking Clopidogrel for several years on the advice of his doctor to prevent coronary heart disease. Ned’s father died from a stroke at age 70, and Ned is in his mid-60s. His physician is now interested in whether “baby aspirin” would be a better medication to prevent a major event like a heart attack or stroke for Ned. 


Step 1 in evidence-based practice is asking a clinical question. The PICO model is a good basis to help you hone in on the different parts of the question you want to ask. You may not be able to fill out every part of the PICO for every question, but it’s a good place to start, and working through the steps can help you make sure you’re not forgetting or overlooking anything important when you go to formulate your search. It can also help you decide which studies you want to consider. 

P: Population

I: Intervention

C: Comparator(s)

O: Outcome(s)

First, we have the population, or how you would describe a group of patients similar to yours. When considering population, you’ll want to think about the conditions, disease severity or stage, comorbidities, and other patient demographics that you’re looking at.   

Next, we have the intervention.  The question here is, which main intervention, prognostic factor, or exposure are you considering?  Important things to think about with the intervention are the dosage, frequency, and method of administration, so that you’ll have as complete a picture as possible of the intervention before starting your search of the literature. 

Next, we have the comparator(s), or, what is the main alternative to compare with the intervention? Useful comparators here could be placebo, usual care, or active control for therapy questions.   

Next, we have outcome(s), or what you can hope to accomplish, measure, improve, or affect.  Here, you’ll want to consider what your patient is interested in knowing.  Do they want to know how it will affect their quality of life? Is morbidity or mortality an important issue here?  Are there harms that your patient might not be aware of that may be of importance? 

Sample PICO

Now, we’re going to apply the PICO model to our case that we talked about above. Take a minute to think about who the patient or population would be in this case. 


Who is the patient?
Ned: 167 votes (22.42%)
Male, mid-60s: 226 votes (30.34%)
Middle-aged with a history of stroke: 352 votes (47.25%)
Total Votes: 745


Ned is, obviously, our patient, but you’re not going to get a lot of search results for “Ned,” or at least, they’re not going to be on-target, so we’ll skip Ned for now.  

Male, mid-60s is a good choice. But, since most study participants are men, it won’t help us a whole lot to limit to men. And mid-60s, while accurate, is a little narrow, so I wouldn’t necessarily pick that one. 

Middle-aged with a family history of stroke is probably the best option here, because these are the two pieces of information that will be the most relevant when we’re formulating our search and later when we’re selecting studies. 


What is the intervention?
Low-dose aspirin: 472 votes (80.82%)
Clopidogrel: 77 votes (13.18%)
Anticoagulants: 29 votes (4.97%)
Placebo: 6 votes (1.03%)
Total Votes: 584


You could pick either low-dose aspirin or clopidogrel here, since we do want to look at both. However, low-dose aspirin is probably the best choice, since it is the new therapy, so it’s the one we really want to look at the evidence for.  

Anticoagulants and placebo are interesting as other comparators, but they’re not what we’re primarily looking at with this question. 


What is the comparator?
Low-dose aspirin: 43 votes (7.76%)
Clopidogrel: 452 votes (81.59%)
Anticoagulants: 29 votes (5.23%)
Placebo: 30 votes (5.42%)
Total Votes: 554


If you picked low-dose aspirin for the intervention, clopidogrel would be the comparator.  If you picked clopidogrel for the intervention, low-dose aspirin would be the comparator.  

Again, anticoagulants and placebo may be other comparators that you may want to look at, but they’re not what we’re primarily interested in today. 


What is the outcome?
Decreased side effects: 19 votes (3.51%)
Cost control: 2 votes (0.37%)
Drug interaction management: 4 votes (0.74%)
Prevention of major CHD event: 517 votes (95.39%)
Total Votes: 542


These are all important outcomes, and they’re definitely ones you would probably consider when making your final decision, but our primary outcome here, based on our case, would be prevention of major CHD event. The other three would be considered secondary outcomes.  So, if low-dose aspirin is as good or better at preventing CHD events than clopidogrel, then you would look at side effects, cost control, etc. before making a final therapy decision, but your primary outcome here is prevention of major CHD event. 

When you put all of this together, you get the following PICO.

P: Middle-aged, family risk factor for stroke

I: Low-dose aspirin

C: Clopidogrel

O: Prevention of stroke or heart attack

Clinical Questions

Once you have your PICO, you can formulate a well-built, answerable clinical question on which to base your searches. Clinical questions can follow this format, though they do not have to:  
In Patient/Population, how does Intervention affect Outcome, compared with Comparator.  

This is just one example of how you might write a clinical question: In middle-aged people with a family history risk for stroke, does daily treatment using low-dose aspirin result in similar rates of prevention of heart attack or stroke compared to Clopidogrel? 

You might not phrase your clinical question exactly the same way, but you do want to try to incorporate as many of your PICO elements as possible when you’re formulating your clinical question.