Critical Appraisal Skills Programme

How to use the PICO Framework to Aid Critical Appraisal

The concept of PICO was introduced in 1995 by Richardson et al. to break down clinical questions into searchable keywords.

The PICO framework and its variations were developed to answer health-related questions. PICO is a mnemonic formula originally developed to help investigators frame research questions when designing a study.

 ElementResearch Question
P Population / Patient / Problem What population or patient group are the investigators working with? It can also refer to the problem being investigated
I Intervention What intervention is the intervention group receiving?
C Comparison / Control Is there a control group, and if so, what intervention is the control group receiving?
O Outcome What outcomes are being measured and how?
  • P stands for “Population or group of patients’ – have the investigators defined which population or patient group they are working with? P can also refer to the problem being investigated, for example, asthma in children.
  • I stands for “Intervention” – did the investigators clearly describe the intervention being given to the intervention group?
  • C stands for “Comparison” – did the investigators include a control group? If so, what was the intervention being given to the control group?
  • O stands for “Outcome/s” – what outcomes of interest did the investigators measure to assess the intervention’s effectiveness, and how were these outcomes measured?

Benefits of the PICO framework

The PICO framework is the most used model for structuring clinical questions because it captures each key element required for a focused question. It can help you form a question that focuses on the most important issue for a patient, problem or a population. It helps to Identify key terms to use in a search for evidence and select results that directly relate to the situation.

Disadvantages of the PICO framework

PICO mostly focuses on intervention (or therapy) clinical questions. It can be less suitable for other question types (such as qualitative research) as It doesn’t account for some complexities like considering feasibility, context, and sociocultural acceptability.

How to use the PICO framework for critical appraisal

PICO can be useful to use in critical appraisal to help identify whether the investigators or researchers conducting a Randomised Controlled Trial (RCT) have been clear about the basic elements of the Research Hypothesis or Research Question.

Alternatives to PICO

There are many other mnemonics out there, but some of the variations of PICO are:


PECO stands for:

  • Population
  • Exposure
  • Comparison
  • Outcome

Compared to PICO, PECO replaces "Intervention" (a planned procedure) with "Exposure" (an unintentional occurrence or happening.)

PECO is a framework for formulating good questions to explore the association of environmental and other exposures with health outcomes.

Example of PECO:

‘I haven't identified an intervention’


PICOC stands for:

  • Patient, Population or Problem - who and/or what is my question focused on?
  • Intervention - what intervention is being considered?
  • Comparison - what intervention is this being compared with? (a comparison is not always necessary)
  • Outcomes - what do you hope to accomplish, improve or affect?
  • Context- in what context or place is the problem set?

Compared to PICO, add a "C" for "Context.

PICOC is a solid strategy for questions relating to cost effectiveness, economic evaluations, service improvements etc.

Example of PICOC:

‘I'm interested in social interventions, ones that are depending on context for effectiveness.’


CoCoPop stands for:

  • Condition - Which condition, disease, problem or symptom are you looking at?
  • Context - When is this happening? Where is this happening? (Geographical location, e.g., England / Service location, e.g., hospital)
  • POPulation - How is your population defined? (e.g., age, gender, ethnic group …)

Example of CoCoPop:

‘I want to look more deeply into the prevalence of a condition, disease, problem, or symptom, but I don't necessarily have an intervention identified or want to compare interventions’


SPICE stands for:

  • Setting - where is the study set e.g., in a specific country, community, in a hospital, in a care home etc.
  • Population or Perspective: from whose perspective is the study done, e.g., the patients, the health professionals., the caregivers, etc.
  • Intervention - what intervention is being examined?
  • Comparison - is the intervention being compared with another?
  • Evaluation - the outcome measures

SPICE is a framework for qualitative questions evaluating experiences, meaningfulness etc.

Example of SPICE:

‘I want to investigate attitudes or opinions.’

Keen to learn more?

To learn more, simply enroll in our affordable online training course ‘Finding and Searching for Evidence


This email address is being protected from spambots. You need JavaScript enabled to view it.
59 Lakeside

Copyright 2024 CASP UK - OAP Ltd. All rights reserved
Website by Beyond Your Brand

This website uses cookies to ensure you get the best experience on our website. Read our Privacy Policy to find out more.