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Systematic Reviews: Critical Appraisal

This guide will help to start and proceed through the main stages of systematic review

Definition

Although, critical appraisal is essentially referred to as a part of the evidence-based process, it does allow systematic assessment of the found evidence. 

Critical appraisal is the process of carefully and systematically examining research to judge its trustworthiness, its value and relevance in a particular context (CASP, 2025). 

Critical appraisal serves to 1) understand is the study good enough to use it for the practice in treating patients; 2) assist in depth evaluation of studies for possible inclusion or exclusion from systematic reviews:

  • reliably support research with high-quality evidence
  • identify useful high-level research relevant to the clinical or health practice
  • better appreciation of how strong the evidence is 
  • reliability, importance and applicability of clinical evidence
  • make informed decision based on assessed findings useful in one own context 
  • improve the quality of healthcare provided to patients
  • make sense of results, efficiency.

(Image source https://www.nccmt.ca/tools/eiph/appraise?utm_source=nccmt&utm_medium=strengthen_your_skills&utm_campaign=registry_additional_resources)

What to Appraise

Research methodology of the article, the field, and type of the study will define which part has to be assessed. Questions below will guide you on how to appraise.

  • Introduction - are there clear aims and objectives? Is the research question clear and focused?
  • Study design/choice of methodology - are they appropriate for what is being measured? Could the hypotheses/aim have been investigated using a different method?
  • Methodology - are there methodological protocols to limit bias? Have participants been appropriately selected? Is the sample size appropriate? Have they followed any protocols for data collection and performing the study?
  • Results and Statistical analysis - is raw data included? Have the findings been analysed accurately? Is there any potential measurement error? Has the reliability been considered? Is statistical significance considered?
  • Discussion/interpretation of results - are these linked back to the study aims? Have null findings been interpreted? Have limitations of the study been considered? Are conclusions/arguments justified by the results data?
  • External validity - can the results be generalised? Are the findings transferable to other settings or limited to the one where they were obtained?
  • Bias - design, sampling, data collection, measurement, reporting, analysis, publication, ethical issues. Has potential bias been addressed? Are conflicts of interest addressed?

How to Appraise

Critical appraisal suggests assessment of the following

  • Aetiology: what caused this illness?
  • Diagnosis: what does this test result mean in this patient?
  • Prognosis: what is likely to happen to this patient?
  • Harm: is having been exposed to this substance likely to do harm, and, if so, what?
  • Effectiveness: is this treatment likely to help patients with this illness?
  • Qualitative: what are the outcomes that are most important to patients with this condition?

The checklists are used to consider the important areas in a consistent, structured way. They should be used depending on the study design (CASP, 2025)

Type of question Study design

Etiology and risk factors

Cohort and case–control studies

Incidence and prevalence

Cohort or cross-sectional

Harm

Cohort and case–control studies

Prognosis

Cohort/survival studies

Value for money

Economic evaluation (e.g. cost-effectiveness study or cost–benefit study)

Effectiveness

Randomized controlled trial

Diagnosis

Diagnostic test study (or randomized controlled trial)

Patient experience (e.g. of illness, treatment or service)

Qualitative studies, e.g. questionnaires, focus groups, or interviews

Checklists

The following tools will assist in successful appraisal assignment, research or practice. They might overlap, see how to select in the upper section of this libguide. It is also suggested to apply the one selected for all materials in a particular assignment to maintain continuity of the project.

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