Systematic Reviews & Meta-analyses: Critical

Guidance on conducting systematic reviews and meta-analyses.


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Cozette Comer, Evidence Synthesis Librarian, Liaison Librarian: Statistics and Computational Modeling & Data Analytics,

Kiri DeBose, Head, Veterinary Medicine Library & Liaison to Animal Sciences,

Ginny Pannabecker, Liaison Librarian: Biochemistry, Biocomplexity Institute, Biological Sciences, Biomedical Engineering and Mechanics, Neuroscience, and Systems Biology; Director, RCE,

Critical Appraisal - Overview and Planning

The critical appraisal process evaluates studies based on quality measures specific to your research question components, the discipline/s related to your research topic, and those specific to the study design, outcome measures, methodology, data analysis, and reporting methods that relate to your research question and identified outcomes.

During the critical appraisal process, you will be assessing each study's risk of bias. See many of the links below to tools often used to critically appraise research studies.  

Critical Appraisal Planning:

  • Identify or Develop one or more checklists or forms for evaluating studies
  • Pilot test one or more checklists or forms for evaluating studies
    • Ensure that you are evaluating all aspects you would like to / need to address
    • Test and ensure inter-rater reliability in evaluating studies

Critical Appraisal Guidance - Example Checklists, Rating Sheets

Cochrane RoB 2.0 (Risk of Bias) Tool

This is the newly revised Cochrane Collaboration Risk of Bias tool, released October 2018.  The Risk of Bias tool developed by the Cochrane Collaboration evaluates studies in several domains, including selection bias, performance bias, attrition bias, reporting bias, etc.  It ONLY can be used for randomized control trials (RCTs).  More information on this tool can be located here: 

Critical Appraisal Skills Programme Tools

  • CASP offers a variety of critical appraisal tools.

NIH Study Quality Assessment Tools

  • The NIH has a variety of study quality assessment tools grouped by study design. 

Joanna Briggs Institute Critical Appraisal Tools

  • Several critical appraisal tools grouped by study design. 


  • Grading Recommendation Assessment, Development, and Evaluation


  • A MeaSurement Tool to Assess systematic Reviews


  • Methodological Expectations of Cochrane Intervention Reviews

Center for Evidence-Based Medicine Critical Appraisal Tools

  • Consolidated Standards of Reporting Trials (CONSORT) Critical Appraisal Checklist

The STROBE Statement for Observational Studies -- Critical Appraisal Checklists

RE-AIM Checklist

  • A checklist that looks at the external validity of intervention programs across the domains of reach, effectiveness, adoption, implementation and maintenance.  

Mixed Methods Appraisal Tools

Non-Randomized Studies

The Newcastle-Ottawa Scale for Assessing the Quality of Nonrandomized Studies

  • A critical appraisal tool for nonrandomized studies. 

Subject/Discipline-based tools

Meta Quality Appraisal Tool (MetaQAT)

  • Public Health studies

SYRCLE's checklist for Animal Studies

  • A checklist (and article) about critical appraisal for animal studies

What kind of bias could I look out for?

This website contains a plethora of biases that you may want to consider for your systematic review. Remember, you don't have to use an established tool if it doesn't work for you. Try creating your own!

Which tool is right for you?

Here's a paper that evaluates 18 critical appraisal tools that are available for researchers to use.  

Tools for assessing risk of reporting biases in studies and syntheses of studies: a systematic review


Background: Several scales, checklists and domain-based tools for assessing risk of reporting biases exist, but it is unclear how much they vary in content and guidance. We conducted a systematic review of the content and measurement properties of such tools.

Methods: We searched for potentially relevant articles in Ovid MEDLINE, Ovid Embase, Ovid PsycINFO and Google Scholar from inception to February 2017. One author screened all titles, abstracts and full text articles, and collected data on tool characteristics.

Results: We identified 18 tools that include an assessment of the risk of reporting bias. Tools varied in regard to the type of reporting bias assessed (eg, bias due to selective publication, bias due to selective non-reporting), and the level of assessment (eg, for the study as a whole, a particular result within a study or a particular synthesis of studies). Various criteria are used across tools to designate a synthesis as being at ‘high’ risk of bias due to selective publication (eg, evidence of funnel plot asymmetry, use of non-comprehensive searches). However, the relative weight assigned to each criterion in the overall judgement is unclear for most of these tools. Tools for assessing risk of bias due to selective non-reporting guide users to assess a study, or an outcome within a study, as ‘high’ risk of bias if no results are reported for an outcome. However, assessing the corresponding risk of bias in a synthesis that is missing the non-reported outcomes is outside the scope of most of these tools. Inter-rater agreement estimates were available for five tools.

Conclusion: There are several limitations of existing tools for assessing risk of reporting biases, in terms of their scope, guidance for reaching risk of bias judgments and measurement properties. Development and evaluation of a new, comprehensive tool could help overcome present limitations.