Step 1: ask

The PICO strategy was developed to help write a clinical question, in order to providing triggers for the identification of terms and assist with searching for evidence. It is designed with treatment questions in mind, but can adapted to answer other clinical question types. The PICO breakdown is as follows:

P: Person, Patient, Population or Problem. This term identifies the type of patient (e.g. gender, age group, race) and the clinical ‘problem’ (e.g. condition, disease) faced.

I: Intervention. This is a more straightforward term, identifying the intervention of interest. However, this term is only relevant to questions related to intervention of some kind, such as therapeutics, lenses or referral for surgery.

C: Comparison. This term applies when the clinical question will ask about one intervention, or perhaps one diagnostic strategy, versus another. When the practitioner is interested in such a comparison, the two interventions/strategies are names as an Intervention and a Comparison.

O: Outcome. The question will refer to an outcome measure or indicator of some kind, such as visual acuity or myopia progression, and this is specified as the Outcome term.

While PICO is a very nice, catchy acronym, we really need to abandon it at times in favour of more appropriate terms. This is explore below regarding the different question types. 

PICO was developed for clinical scenarios in which intervention is being considered, so application is easy. When we do not want to compare different types of intervention, we do not need to identify a Comparison ("C") term, reducing PICO to PIO.

If we are not asking about an intervention of any kind (such as when we are interested in prevalence, or diagnosis) we do not need to include the “I” term.

Instead, it is appropriate for some questions to add other letters, such as :

• "N" for Number in questions of prevalence or magnitude. 
• "R" for Risk factor in questions of aetiology, and
• "T" for Test method in questions of diagnosis.

Each of these different types of question is demonstrated as part of an interactive case study. 

One of the benefits of careful and thoughtful question-forming is that the search for evidence is easier. The well-formed question makes it relatively straightforward to determine the appropriate terms needed to find information in the language of whichever searching service is available to you (e.g. Medline; see Step 2). Using PICO also helps you determine the search terms to use and helps you find specific articles to answer your question, meaning you find and need to read what is relevant. PICO is a great start to help you answer your clinical question whilst saving time!

P: Person, Patient, Population or Problem.

• Who are the relevant patients?
• Describe the ones that you come into contact with and are relevant to your practice. These populations might be the most relevant in writing your next clinical question.

I: Intervention.

• What is the intervention, treatment, test etc. that you are interested in? Interventions can be types of dressings, drug therapies, placebos or counselling. Also they can be about the provision of differing environmental factors or deal with the way in which information is given to patients. They can also be diagnostic tests.
• Depending on what you already know about the topic you may want to investigate the name of a particular treatment or test (for example, laser treatment or lutein supplementation). Alternatively if the patient or population is relatively new, you can keep this general and ask "what intervention" rather than specifying a specific known treatment or test. 

C: Comparison Intervention.

• Is there an alternative strategy to compare with the intervention? This can be a standard therapy, though it may also be no intervention a placebo or an alternative treatment, exposure or diagnostic test.

O: Outcomes.

• What are the consequences of the interventions you are interested in? Make a distinction between the outcome which is relevant to your patient or problem and the outcome measures deployed in studies. Spend some time working out exactly what outcome is important to you, your patient, and the time-frame which is appropriate.