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Planning a Literature Review

Refine Your Research Question

The purpose of a systematic review is to answer a clear and focused question. Translating a knowledge gap into an answerable and soundly constructed question is an important skill. The review question should be defined at the beginning your systematic review. A well formulated review question will help determine your inclusion and exclusion criteria, the creation of your search strategy, the collection of data and the presentation of your findings. A sound clinical question:

  • Allows you to find information quickly.
  • Allows you to find information that is relevant (applicable to the patient) and valid (accurately measures stated objectives).
  • Provides you with a checklist for the main concepts to be included in your search strategy.

The question should always be:

  • Clear
  • Unambiguous
  • Structured

It is important to formulate your research question with care so as to avoid missing relevant studies or collecting a potentially biased result set. To do that, use a framework such as the 5Ws (Who - What - When - Where - Why) or PICO (Problem/Patient/Population - Intervention - Comparitor - Outcome) to explore all aspects of your topic before you begin dedicating yourself to searching and synthesizing information. PICO It is typically used for evidence-based medicine whereas the 5Ws are used widely in other disciplines. Using a framework to map out your research question will help you to ensure that your search for evidence is structured, systematic and complete.

PICO or PICo are useful tools for defining clear, focused clinical questions and developing a review protocol. Before defining your question using PICO or PICo, you should check that your question has not already been the subject of a systematic review.

What if you want to change things later?

A protocol for a systematic review should only be modified if it becomes clear that there are alternative ways of defining your population, intervention, outcomes or study designs.

Population or Problem Intervention or Exposure Comparison Outcome

What are the characteristics of the population or patient?

What is the problem, condition or disease you are interested in?

How do you wish to intervene - what do you want to do with this patient - treat, diagnose, observe, etc.? What is the comparison or alternative to the intervention - placebo, different drug or therapy, surgery, etc.? What are the possible outcomes - morbidity, death, complications, etc.?

To develop an effective search strategy, use the PICO worksheet below.

This includes identifying:

  • Type of study
  • Limitations
  • Keywords or synonyms
  • Which database/s to search

Here is an example of a clinical question that outlines the PICO components:

P = middle-aged male amputee suffering from phantom limb

I = is gabapentin

C = compared with placebo

O = effective in decreasing pain symptoms?

Identify Sources

Once you have a clear idea about what you want to research, begin identifying key studies, sources, databases, reports and books to use. You can start searching for sources using the library website which includes access to databases, journals, magazines, streaming media, newspapers and more.

Multiple resources should be searched (example, no less than 3 databases) and grey literature should be included in order to reduce publication bias. As you are searching, use a citation management program such as Zotero and/or research log to track sources. Use this example spreadsheet to get started. Using a research log will help to:

  • Reduces information fatigue
  • Helps you avoid duplicating searches you've already done
  • Gives you ideas for further search strategies and keywords
  • Helps you reconstruct searches later if you need to
  • Saves you from trying to remember where and what you've already searched!
  • Important for semester-long projects, theses, dissertations and group projects.

When selecting sources, consider: 

  • Authority/Provenance: What are the author's credentials? Are the author's arguments supported by evidence (e.g. primary historical material, case studies, narratives, statistics, recent scientific findings)?
  • Objectivity: Is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
  • Persuasiveness: Which of the author's theses are most/least convincing?
  • Value: Are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

Evaluate & Analyze

Data Evaluation

This involves a quality assessment of the sources selected and is relevant to every step of a review. When doing this step, you are determining which literature makes a significant contribution to the understanding of the topic. The risk of publication bias and related biases should also be explored. Any recommendations should be considered in connection to its strengths and weaknesses of evidence.

Analysis and Interpretation

This final steps will be your narrative of the findings and any conclusions of pertinent literature and may also data tabulation.