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Systematic Search for Systematic Review

This guide aims to provide advice and resources for doing a systematic review.

Worksheets for Documenting & Reporting Search Process

Here are some resources for you to document and report your search process in a systematic review. 

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PICO

A systematic review aims to answer a specific research (clinical) question. A well-formulated question will guide many aspects of the review process, including determining eligibility criteria, searching for studies, collecting data from included studies, and presenting findings (Cochrane Handbook, Sec. 5.1.1).

To define a researchable question, the most commonly used structure is PICO, which specifies the type of Patient or Population, type of Interventions (and Comparisons if there is any), and the type of Outcomes that are of interest. 

The table below gives an example on how a research question is framed using the PICO structure. You may also use the PICO components to write the objective and title of your review, and later to structure your inclusion and exclusion criteria for study selection. This ensures that the whole review process is guided by your research question. 

  P
(Patient or Population or Problem)
I
(Intervention, prognostic factor, exposure)
C
(Comparison)
O
(Outcomes)
Intention State the disease, age and gender, if appropriate, of the population. State the intervention and specifics related to it. A therapeutic question always has a comparator (even if it is standard care). What is being looked for or measured?

Example

(a therapeutic question)

Women who have experienced domestic violence Advocacy programmes General practice or routine treatment Quality of Life (measured by the SF-36 scale)
Research question: For women who have experienced domestic violence, how effective are advocacy programmes as compared with routine general practice treatment for improving women's quality of life (as measured by the SF-36 scale)?
Objective: The purpose of this review is to evaluate the effectiveness of advocacy programmes as compared with routine general practice on the quality of life of women who have experienced domestic violence.
Title: The effectiveness of advocacy compared with routine general practice treatment for women who are or have previously experienced domestic violence: a systematic review of women's quality of life.
Reproduced from: Bettany-Saltikov, J, (2010). Learning how to undertake a systematic review: part 1. Nursing Standard. 24(50), 47-55.

Type of Question and Study Design

While formulating your research question, it's also important to consider the type of question you are asking because this will affect the type of studies (or study design) to be included in your review.

Each type of question defines its type of studies in order to provide the best evidence. For example, to answer a therapeutic question, you need to include as many Randomized Controlled Trials (RCTs) as possible, because RCTs are considered to have the highest level of evidence (least bias) for solving a therapeutic problem. 

The table below suggests the best designs for specific type of question. The Level of Evidence pyramid, which is widely adopted in the medical research area, shows a hierarchy of the quality of medical research evidence in different type of studies (Level of Evidence (2011), Oxford Centre for Evidence-based Medicine, CEBM).

Type of Question Ideal Type of Study 
(or Study Design)
Level of Evidence

Therapy / Intervention

RCT > Cohort Study > Case Control Study > Case Series Level of Evidence

Diagnosis

Cross-sectional Study (with consistently applied reference standard and blinding)

Prognosis

Cohort Study > Case Control Study > Case Series

Etiology / Harm

RCT > Cohort Study > Case Control Study > Case Series

Usually, the study design of a research work will be clearly indicated either in its title or abstract, especially for RCT. Some databases also allow to search or refine results to one or a few study designs, which helps you locate as many as possible the relevant studies. If you are not sure the study design of a research work, refer to this brief guide for spotting study designs (by CEBM).

Learn to Build a Good Clinical Question

Learn to build a good clinical question from this EBP Tutorial: Module 1: "Introduction to Evidence-Based Practice"

It is provided by Duke University and University of North Carolina at Chapel Hill, USA.

PICO Framework and the Question Statement
The above named section in the Library guide: Evidence-Based Practice in Health, provided by the University of Canberra Library, explains the PICO framework with examples and in various question types.

Documenting Your Search Process

Systematic review requires a detailed and structured reporting of the search strategy and selection criteria used in the review. Therefore we strongly advise you to document your search process from the very beginning. You may use this workbook to help you with the documentation.

The documentation should include:

  • Research concepts in PICO structure and research question,
  • Type of studies you intend to include, and
  • Inclusion and exclusion criteria in PICO structure

and the whole search process, including:

  • Databases searched (hosting platforms), including journals and other sources covered in handsearching
  • Date of search
  • Search strategy, including keywords and subject headings used, the combination of searches (usually copy-paste from database search page)
  • Filters used in initial search or refine results, including year coverage, type of studies, age, etc.
  • Number of results retrieved after each search and refinement in each database
  • Total number of results from all databases searched
  • Duplicates identified from all results
  • Number of results with full text

Eventually, you will need to include the information above when you start writing your review. A highly recommended structure for reporting the search process is the PRISMA Flow Diagram. You may also use PRISMA Flow Diagram Generator to generate a diagram in a different format (based on your input).