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Systematic Reviews and Related Evidence Syntheses

What is a Proposal?

The proposal stage is the most important step of a review project as it determines the feasibility and rationale for the review and focuses the scope. Activities include:

  1. Selecting the appropriate review type (narrative? systematic? scoping?)
  2. Developing the research question
  3. Defining the eligibility criteria of studies that will be included in your review
  4. Scoping search
  5. Feasibility assessment and proposal summary

 Watch JBI: Pre-planning and protocol development for systematic reviews which discusses planning between 4 minutes and 30 seconds and 17 minutes

(1) Selecting the Appropriate Review Type

  • Prioritizing the Review Method: If a systematic review is your goal, be prepared to adjust your research question to align with its specific requirements i.e. reframing the question or limiting to studies only.
  • Prioritizing the Research Question: If your research question is the primary focus, select the review method that best achieves your research goals. Over twenty review types exist. Key types are defined on the About page.  

Similarity of Included Studies

  • Systematic reviews require homogeneity among the studies you include. They do not have to be identical study types, but they should share a similar perspective. The more heterogeneous the studies, the less appropriate a systematic review becomes.
  • Scoping/Mapping reviews are mostly descriptive and can therefore accommodate more diverse study types. 

Tools and Resources for Selecting Review Type

(2) Research Question & (3) Eligibility Criteria

The review question needs to be clearly and specifically stated within a framework (PICO, PEO, PCC, etc.) that identifies key concepts and ensures the research question is specific, answerable, and aligned with the goals of your review.

  • Scoping reviews primarily utilize the PCC (Population, Concept, Context) framework
  • Systematic reviews offer a wider range of frameworks (PICO, PEO, CoCoPop, etc.)

In selecting the framework, the eligibility criteria will also need to be determined. 

Eligibility criteria - characteristics that studies must possess to be included in your review​ consisting of:

  • Inclusion: characteristics for included articles, can be limiters such as years 
  • Exclusion: exceptions to inclusion criteria (not just opposite of inclusion criteria)

The eligibility criteria closely align with the components of your question framework and may include additional criteria such as type of study or setting.

PCC is a question framework recommended by Joanna Briggs Institute (JBI) for scoping reviews (Peters et al., 2020). 

Example question

  • What factors related to counselor bias and contraceptive counseling for women have been reported?

Population: "Important characteristics of participants, including age and other qualifying criteria" (11.2.4)

  • counselors who provide contraceptive counseling to biological female patients

Concept: The core concept which "should be clearly articulated to guide the scope and breadth of the inquiry. This may include details that pertain to elements that would be detailed in a standard SR, such as the 'interventions' and/or 'phenomena of interest' and/or 'outcomes'" (11.2.4)

  • biases related to contraceptive counseling

Context: "May include...cultural factors such as geographic location and/or specific racial or gender-based interests. In some cases, context may also encompass details about the specific setting."

  • any setting where health education may be provided

 

Reference: Peters MDJ, Godfrey C, McInerney P, Munn Z, Tricco AC, Khalil, H. Scoping Reviews (2020). Aromataris E, Lockwood C, Porritt K, Pilla B, Jordan Z, editors. JBI Manual for Evidence Synthesis. JBI; 2024. Available from: https://synthesismanual.jbi.global.  https://doi.org/10.46658/JBIMES-24-09

PICO is a commonly used question framework for systematic reviews of effectiveness.

  • Aim: to evaluate the effectiveness of a certain treatment/practice in terms of its impact on outcomes

Example question

  • What non-pharmacological interventions (including cognitive, physical exercise, art/music/dance therapies, and nutritional interventions) are effective at slowing the progress of mild cognitive impairment?
    (Source: Foster, M. J., & Jewell, S. T. (2022). Piecing together systematic reviews and other evidence syntheses. Rowman & Littlefield.)

P (Population): Can also be Patient(s), Problem, Participants

  • people with mild cognitive impairment

I (Intervention): 

  • non-pharmacological interventions to slow progression

C (Comparator): or Control

  • none

O (Outcome): 

  • slowing the progress of mild cognitive impairment

 

Familiar variations of PICO include PICOT (timeframe), PICOS (study type), and PICOC (context). 

PEO is a commonly used question framework for systematic reviews of etiology and/or risk.

  • Aim: to determine the association between particular exposure/risk factors and outcomes

Example question

  • In residents of low-income urban neighborhoods, what is the impact of implementing community gardens on social cohesion and community engagement?

P (Population):

  • Residents of low-income urban neighborhoods

E (Exposure):

  • Implementation of community gardens within these neighborhoods

O (Outcome):

  • Changes in social cohesion and community engagement

Etiology or Risk

PECO: Population, Exposure, Comparator, Outcome
Example: Among newborns, what is the incremental effect of 10 dB increase during gestation on postnatal hearing impairment?

From Morgan, R. L., Whaley, P., Thayer, K. A., & Schünemann, H. J. (2018). Identifying the PECO: A framework for formulating good questions to explore the association of environmental and other exposures with health outcomes. Environment international, 121(Pt 1), 1027–1031.

Prevalence and/or Incidence

PCS: Population, Condition, Setting or Context
CoCoPop: Condition, Context, Population
Example: What is the prevalence/incidence of claustrophobia and claustrophobic reactions in adult patients undergoing MRI?

Diagnostic Test Accuracy

PIRD: Population, Index Test, Reference Test, Diagnosis of Interest
Example: What is the diagnostic test accuracy of nutritional tools (i.e. Malnutrition Screening Tool) compared to the Patient Generated Subjective Global Assessment amongst patients with colorectal cancer to identify undernutrition?

Costs / Economic Evaluation

PICOC: Population, Intervention, Comparator(s), Outcomes, Context
Example: What is the cost effectiveness of self-monitoring of blood glucose in type 2 diabetes mellitus in high income countries?

Experiential (Qualitative)

PICo: Population, phenomenon of Interest, Context
Example: What are the policy strategies to reduce maternal mortality in pregnant and birthing women in Cambodia, Thailand, Malaysia, and Shri Lanka?

Social Sciences (Qualitative)

SPICE: Setting, Perspective, phenomenon of Interest, Comparison, Evaluation
Example: From the perspective of an undergraduate student (perspective) in a university library (setting), is provision of a short term loan collection (intervention) more effective than a general collection (comparison) in terms of the percentage availability of recommended texts (evaluation)? (Booth, 2006)

*This is not an exhaustive list. See "What kind of systematic review should I conduct? A proposed typology and guidance for systematic reviewers in the medical and health sciences" by Munn et al., (2023) for more frameworks. 

The same research question can be adapted into different frameworks: 

What are the effects of Vitamin-D on obesity?

PICO 1

  • Patient: obesity​

  • Intervention: vit D​

  • Outcome: effects​

  • Study design- RCTs

PICO 2

  • Patient: age group/other​

  • Intervention: vit D​

  • Outcome: obesity​

  • Study design- cohort (follow over time)​

PEO

  • Population: obesity​

  • Exposure: Vit D​

  • Outcome: effects​

  • Study design- surveys (cross sectional)​

PCC (Scoping Review)

  • Population: Obesity​

  • Concept: Vit D intake​

  • Context: could be a setting, geography, population, age group​

  • No set study design​

(4) Scoping Search

The scoping search: 

  • Locates related reviews
    • which helps place yours in the context of others
    • discovers if your research question has already been addressed effectively by another review
  • Locates eligible studies that can help further refine eligibility criteria (thereby clarifying your research question)
  • Estimates the number of articles expected in the final comprehensive searches

To identify the most relevant databases for your research, consult a librarian. Sharing articles that closely match your research interests will aid in search development. They can also help you expand keywords and subject headings for a more comprehensive search.

Finding and Evaluating Related Reviews

Before starting a review, it's essential to explore existing literature. Start with a broad keyword search — remember, relevant reviews may not always be labeled as "systematic" in the title.

If related reviews are found, evaluate them critically. This serves two main purposes:

  1. Clarify Rationale: Show how your review will add unique value
  2. Define Scope: Avoid redundancy by understanding what has already been addressed

Use a table like the one below to document key characteristics of each review:

ID Review Type Review Question Search Scope Eligibility Criteria Outcomes

Author(Year) 

 Systematic Review What is the effectiveness of X on Y? Databases and concepts/keywords  searched Adults with condition Z; intervention A vs placebo Mortality, quality of life

This table will help you map the review landscape and determine whether your proposed review is needed or duplicative. If you discover several related reviews, carefully assess their quality as well using the tools below. 

Tools for Assessing the Quality of Reviews

  • ROBIS (Risk of Bias in Systematic reviews)

  • AMSTAR: Assessing the Methodological Quality of Systematic Reviews

  • CASP Checklist: Critical Appraisal Skills Programme

Where to Search for Related Reviews

Campbell Collaboration 
Reviews in education, business, social policy, and more.
Cochrane Library 
High-quality systematic reviews focused on clinical interventions.
PROSPERO 
International registry of systematic review protocols in health and care.
JBI Systematic Review Register 
Registered reviews from JBI-affiliated researchers in healthcare.
Open Science Framework 
Open-access registry for all types of research, including reviews.
Collaboration for Environmental Evidence 
Environmental research reviews and guidance for authors.
SYREAF 
Systematic reviews and protocols in animal and food-related sciences.
Tip:
Also search subject-specific databases using the keyword “review”.

A scoping search is a quick, exploratory search designed to give you a broad overview of the available literature and help you refine your research question.

Why Conduct a Scoping Search?
  • Clarify Your Research Question: it helps further clarify your research question by identifying the range and types of studies available
  • Develop Eligibility Criteria: the literature you find will provide examples of eligible studies, which you can use to refine your eligibility criteria
  • Estimate Search Volume: it allows you to estimate the number of articles you can expect with your final, more comprehensive searches
  • Aid Librarian Consultation: providing your librarian with studies that closely match your eligibility criteria, assists in search strategy development
  • Assess Literature Availability: A lack of relevant studies may indicate that your eligibility criteria need to be adapted or that there is insufficient literature on your topic
How to Conduct a Scoping Search
  1. Target the Primary Database: Conduct your search in the most important database for your research topic
  2. Review a Manageable Sample: Sort through 50–100 results (if using Covidence). This sample should help you:
    • Identify potential studies for inclusion
    • Provide exemplars for your final search strategy
    • Ensure that the relevant studies align with your review's focus, and are not just background information
  3. Adjust Based on Findings:
    • Too Few Studies: Broaden your concept(s) to capture a wider range of literature
    • Too Many Studies: Refine your search by limiting it to specific populations, interventions, or time periods

Quick Exploration: Think of this as a preliminary sweep of the literature. It's not meant to be exhaustive, but rather a snapshot of what's out there

Estimate Review Timeline: The number of citations you find will give you a rough estimate of the time required to complete your review

(5) Feasibility Assessment & Proposal Summary

Feasibility can be determined after framing the question, determining eligibility criteria, and evaluating previous reviews.

TREAD helps authors evaluate review project feasibility

Time (T): How long? The average systematic review takes 12–18 months. The number of citations to be sorted and experience conducting reviews impacts timeframe. Estimated screening time: titles/abstracts = 30–50/hour, full-text = 10–25/hour, data extraction & critical appraisal = 1–3 hours per study.

Resources (R): This can include software (Covidence, citation management), funding, human capital (do you have a team?), and time investment.

Expertise (E): Do you have experience with systematic reviews, tools, or statistical methods? Expertise is critical for quality and efficiency.

Audience (A): Who are you producing this for? Researchers, the public, policy makers? Clarifying this helps shape scope and language.

Data (D): Are there enough data (studies) to conduct the review? Consider how you will manage and preserve data throughout the process.

From Booth, A., Sutton, A., & Papaioannou, D. (2016). Systematic Approaches to a Successful Literature Review. 2nd ed. Sage. 

Proposal Summary

A written proposal helps in framing the project and getting feedback and should include:

  • A descriptive title of project, which includes the type of review
  • A brief introduction
  • A description of previous reviews and the rationale for the proposed review
  • An appropriate framed question for the review
  • The eligibility criteria