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Systematic Reviews: Overview of systematic reviews

Overview of systematic review methodology and key strategies for searching and reporting to the Cochrane Collaboration's Gold Standard

Heading: Overview of systematic reviews

Overview of systematic reviews

This guide will explain the process of conducting a systematic review in more detail as well as provide you with relevant resources for your review.

Move through the slide deck below to get an overview of systematic reviews. Alternatively, download the PDF document at the bottom of this box.

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The elements of a systematic review

What are the different elements of a systematic review?

What is it?

A systematic review attempts to identify, appraise and synthesise all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit and reproducible methods aimed at minimising bias in the review process, in order to produce more reliable findings that can be used to inform decision making.

Reasons for choosing

To address a clearly focused review question by finding the best available, relevant research studies and synthesising the results.

Question

Focused on a single topic.

Sources / Search

A peer review protocol or plan is included. Clear objectives are identified. Comprehensive sources and explicit and reproducible search strategy.

Eligibility criteria

Eligibility criteria is clearly defined at the outset i.e. before the review is conducted.

Selection

Criterion-based selection that is uniformly applied, clear and explicit.

Appraisal

Rigorous critical appraisal, and evaluation of study quality.

Synthesis

Clear summaries of studies based on high quality evidence.

Inferences

Evidence based.

A meta-analysis is a statistical process for amalgamating the data from different primary studies which have investigated the same issue, using suitably homogenous data.

Note that while most meta-analyses arise from a systematic review of the literature, it possible to perform a meta-analysis without doing a systemic review.

Watch the following video by Dr Saravana Kumar, Associate Professor in Physiotherapy, UniSA, to learn more.

Video Length: 4:44

  • Systematic reviews and meta-analyses are not the same.
  • A systematic review may include a meta-analysis.
  • A meta-analysis can be created on its own, but usually they are part of a systematic review.
  • A systematic review is a process to:
    • determine a question
    • set inclusion and exclusion criteria
    • find and select the literature
    • critically appraise and synthesise the literature
  • Meta-analysis is a statistical process to:
    • synthesise findings from many studies which all investigate a similar issue
    • summarise the effects of all the different studies
    • address the limitations of individual studies (e.g. small sample sizes)
  • A meta-analysis can only be done for studies with homogenous (similar) data.
  • For heterogenous studies (different data), use descriptive synthesis instead.
Type
Overview
Narrative review
(literature review) 

Synthesises the findings of literature retrieved from searches of computerised databases, hand searches, and authoritative texts.

Critical review

Shows that the literature has been extensively researched and critically evaluated. Goes beyond the narrative review as it contains a degree of analysis and conceptual innovation of the literature.

Scoping review

Aims to provide an overview or map of the available evidence, focusing on concepts, themes and types. Conducted according to similar rigorous and transparent methods as systematic reviews, but typically answers broad questions and does not require critical appraisal.

Rapid review

Uses systematic review methods to search and critically appraise the literature to assess what is already known about a particular policy or issue. How complete the searches are depends on time factors.

Systematic review

Attempts to identify, appraise and synthesise all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit and reproducible methods aimed at minimising bias in the review process, in order to produce more reliable findings that can be used to inform decision making.

Umbrella review

Focuses on a broad condition or problem and compiles evidence from other reviews into one document which highlights competing interventions. Does not include primary studies.

Adapted from: 'A typology of reviews' (Grant and Booth 2009, pp. 94-5).

The systematic review in context:

Systematic reviews level of confidence graph. Systematic reviews have the highest level of confidence.

Original image source: HLWIKI International, adapted under Creative Commons (CC BY-NC-SA 2.5 CA)

Guidelines and standards

Using a standard or guidelines will help you conduct your systematic review. 

Cochrane Library logo Campbell Collaboration logo Finding what works in health care book cover

Cochrane Library logo

“The process of preparing and publishing a Cochrane Review is different from that for other journals. Reviews are typically registered at conception and there is a closer working relationship between Cochrane and the review authors. In addition, Cochrane Reviews follow a highly structured format so that they can be published within the Cochrane Database of Systematic Reviews, and their preparation follows a structured process.”

-Cochrane Handbook, Part 1, Chapter 2.1.

Campbell Collaboration logo

The process


This is the plan for your review.

  • Search strategy and databases
  • Eligibility criteria
  • Screening process
  • Critical appraisal process
  • Data analysis / synthesis process
  • Register your protocol (e.g. with Prospero or Open Science Framework) or publish it in a relevant journal.

Then, per your protocol:

Further resources