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PICO Framework for Systematic Reviews: A Comprehensive Overview

What is a systematic review?

Before diving into the meaning of a PICO framework systematic review, it is important to have a quick overview of the meaning of a systematic review. You have probably come across the hierarchy of evidence, which is used to rank the strength of evidence obtained from research studies to power clinical decision-making. Systematic reviews (and meta-analyses) are usually placed at the top of the pyramid as the highest level of evidence. For this reason, many universities are accepting systematic reviews and meta-analyses for undergraduate, masters, and PhD dissertations. Similarly, many reputable academic journals are accepting systematic reviews and meta-analyses as a source of credible evidence for publications.

A systematic review is the highest level of evidence, especially in clinical sciences. It aims to answer focused clinical questions to power evidence-based clinical decision-making by collating findings from various empirical studies. These empirical studies must meet a pre-specified eligibility criteria. Therefore, when doing a systematic review, the first step is to formulate a research question. That is where the idea of a PICO framework emerges.

What is PICO Framework Systematic Review?

In summary, when formulating a research question to be answered using a systematic review methodology, you must follow a specified structure. One of the frameworks commonly employed in formulating systematic review research questions is the PICO framework. Similarly, the empirical studies whose findings are collated in a systematic review must meet pre-specified eligibility criteria. Also, the PICO framework is used in guiding the formulation of these eligibility criteria. Therefore, before describing the specific meaning of the PICO framework, it is important to note its two functions in systematic reviews, namely (a) framing research questions and (b) formulating eligibility criteria. The PICO framework is recommended by the Cochrane Collaboration in framing research questions and formulating eligibility criteria.


PICO framework systematic review

A PICO Framework systematic review refers to a systematic review or meta-analysis that relies on the PICO process.

The Elements of the PICO Framework


The “P” element of PICO refers to the target population of your research. For example, you could be focusing on adults diagnosed with diabetes. In your research question, you must indicate that you systematic review is focusing on adults diagnosed with diabetes. Similarly, in your eligibility criteria, you must indicate that you’re selecting only empirical studies that used adults diagnosed with diabetes in their sample. Thus, studies that use a sample of children or adolescents diagnosed with diabetes may not meet your eligibility criteria.


The “I” element of PICO defines the intervention whose effects you’re investigating in your systematic review. For example, as a clinician or researcher, you might be interested in understanding the effectiveness of interventions derived from self-determination theory for adults diagnosed with diabetes. In this regard, the specific interventions are not yet identified. In that case, you can add an objective to your systematic review about identifying or summarizing interventions derived from the self-determination theory. Therefore, in your eligibility criteria, you must also mention that you’re only focusing on interventions derived from the self-determination theory. In other words, studies to be selected in your systematic review must focus on investigating such interventions.


The “C” element of a PICO framework outlines the comparison. In this case, the comparison refers to the alternative that you’re comparing your intervention against. Take the example of a systematic review investigating the effectiveness of interventions derived from the self-determination theory. For you to determine whether such interventions are effective, you can compare them with usual or routine care. If the intervention shows better effectiveness than usual or routine care, you can recommend it in your systematic review.


Finally, the “O” element of the PICO framework refers to the outcome, which defines the specific outcome or result you want to measure. In the case of a systematic review focusing on adult patients diagnosed with diabetes, interventions derived from self-determination theory, and usual treatment as the comparison, the outcome can include self-management. In other words, you want to determine the extent to which the intervention improves self-management among adult patients diagnosed with diabetes.

Framing a Research Question in a PICO Framework Systematic Review

In systematic reviews and meta-analyses, the PICO framework is commonly used to frame a research question. To do so, you must start by defining the PICO elements. In most cases, the population of interest is known by a clinician or researcher. The intervention may be known or unknown. The comparison is also usually known, in most cases determined as “usual care” in various healthcare settings. Finally, in most cases, the outcome(s) is unknown, but it can also be pre-defined.

What I mean in this case is that, sometimes the researcher or clinician may be interested in identifying interventions (unknown) that bring about a certain outcome or results in a given target population. Since the intervention is unknown, the researcher can formulate the research question to imply that they are investigating interventions that bring about a certain effect. For example, “In adults diagnosed with diabetes (P), which interventions (I), compared to usual care (C), can improve self-management? (O)” In such a research question, the researcher or clinician knows the population, the comparison, and the outcome, but does not know the interventions, which will be the focus on their systematic review.

However, in most cases, the researcher knows the population, intervention, and comparison, but does not know the outcomes. For instance, “In adults diagnosed with diabetes (P), compared to usual care (C), what is the effectiveness of self-determination-based interventions (I) in improving self-management?” In this case, the researcher does not know whether the identified interventions improves self-management or not. It is important noting that any element of the PICO framework can be unknown.

Formulating Eligibility Criteria in a PICO Systematic Review

Apart from framing a research question, the PICO framework can also be used in formulating eligibility criteria for systematic reviews. Take the example of a systematic review focusing on the effectiveness of self-determination theory-based interventions for improving self-management in adults diagnosed with diabetes. The eligibility criteria derived from the PICO framework can be as follows:

  • Population – Adult patients diagnosed with diabetes. Therefore, studies using a sample of children or adolescents were excluded in the systematic review.
  • Intervention – Studies investigating the effectiveness of interventions derived from self-determination theories. Studies investigating interventions derived from other theoretical or conceptual models other than the self-determination theory will be excluded.
  • Comparison – Studies comparing the intervention with usual care or routine management of adult patients with diabetes. In most cases, researchers are lenient defining the specific comparison used in studies.
  • Outcome – Studies investigating the effectiveness of the intervention in improving self-management in adult patients diagnosed with diabetes. Studies not reporting on this outcome will be excluded from the meta-analysis.


The four elements above are usually combined with study design, year of publication, and article language to formulate a complete eligibility criteria in PICO framework systematic reviews. The PICO framework guides the formulation of an eligibility criteria that can be used to select empirical studies that can answer a specific research question for clinical practice decision-making.

The PICO Framework for a Literature Search Strategy

Finally, the PICO framework can be used in developing a literature search strategy. However, its use for this purpose is highly contentious. Some argue that when developing a search strategy, the outcomes should not be captured because they can lower the retrieval potential of that search strategy. Instead, the keywords used should only focus on the population and intervention elements. The outcomes will be determined when screening the articles for eligibility. Because of such disagreements among scholars, we did not include the development of a literature search strategy as one of the functions of a PICO framework in systematic reviews. Even so, we heavily recommend experimenting first. For example, you can harvest keywords relevant to each of the PICO elements. In the first search round, include keywords for population and intervention elements only. In the second round, introduce keywords from other PICO elements.

Research Question Types Suitable for PICO Systematic Reviews

There are different types of systematic reviews depending on the type of research question being answered. Some research question types are suitable for other frameworks like SPIDER and CIMO. Other research questions are strictly suitable for a PICO framework. Therefore, before choosing PICO as your preferred framework, it is important to begin by determining whether the type of your research question is suitable. The following types of research questions are suitable for a PICO framework systematic review:

PICO systematic review

Once you have identified the suitability of PICO for your research question, the next step is to formulate the research question accordingly. The table below provides a detailed guidance on how to frame each question type based on the PICO framework:

pico example


PICO framework systematic reviews are those whose research questions and eligibility criteria are derived from the PICO framework. The PICO framework is one of the most common frameworks used in systematic reviews because it ensures research questions and eligibility criteria are not too specific or too broad.


  1. Frandsen, T. F., Bruun Nielsen, M. F., Lindhardt, C. L., & Eriksen, M. B. (2020). Using the full PICO model as a search tool for systematic reviews resulted in lower recall for some PICO elements. Journal of Clinical Epidemiology, 127, 69–75. https://doi.org/10.1016/j.jclinepi.2020.07.005
  2. Higgins, J. P. T., Thomas, J., Chandler, J., Cumpston, M., Li, T., Page, M. J., & Welch, V. A. (Eds.). (2019). Cochrane handbook for systematic reviews of interventions (1st ed.). Wiley. https://doi.org/10.1002/9781119536604
  3. Mathiesen, A. S., Zoffmann, V., Lindschou, J., Jakobsen, J. C., Gluud, C., Due-Christensen, M., Rasmussen, B., Marqvorsen, E. H. S., Lund-Jacobsen, T., Skytte, T. B., Thomsen, T., & Rothmann, M. J. (2023). Self-determination theory interventions versus usual care in people with diabetes: A systematic review with meta-analysis and trial sequential analysis. Systematic Reviews, 12(1), 158. https://doi.org/10.1186/s13643-023-02308-z
  4. Scells, H., Zuccon, G., Koopman, B., Deacon, A., Azzopardi, L., & Geva, S. (2017). Integrating the framing of clinical questions via PICO into the retrieval of medical literature for systematic reviews. Proceedings of the 2017 ACM on Conference on Information and Knowledge Management, 2291–2294. https://doi.org/10.1145/3132847.3133080
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