How to critically appraise a scientific paper (medical journal)

Hi everyone,

Welcome back to my blog post series, today’s topic is How to read a critically appraise a scientific paper (medical journal).

 Firstly, it is important to understand why we critically analyse papers. One of the main reasons is to determine if this paper is trustworthy. Are findings of this paper generalizable and applicable to a clinical or hospital setting?

 Critical appraisal also allows us to:

  • Reduce information overload by eliminating irrelevant or weak studies
  • Identify the most relevant papers
  • Distinguish evidence from opinion, assumptions, misreporting, and belief
  • Assess the validity of the study
  • Assess the usefulness and clinical applicability of the study
  • Recognise any potential for bias.

*Note a critical appraisal of a paper is your critical reflection on the academic work.  To determine the level of bias or the quality of the paper you will need to conduct a “Risk of Bias Assessment” or “Methodological Quality Assessment” of the paper. These will be discussed in later blogs

When critically analyzing a paper the specific questions used to assess validity will change slightly depending on the study designs and article types.

The checklist I have devised (below) is general and suitable to most study designs. It can be used as a quick reference to appraise any journal article.

The first four checklist questions should be answered “Yes.” If any of the four questions are answered “No,” then this article is not suitable for your research.  I would suggest that you return to your search and attempt to find an article that will meet these criteria.

Critical appraisal of…the Introduction

  1. Does the article attempt to answer the same question as your clinical question?
  2. Is the article recently published (within 5 years) or is it seminal (i.e. an earlier article but which has strongly influenced later developments)?
  3. Is the journal peer-reviewed?
  4. Do the authors present a hypothesis?

Critical appraisal of…the Methods

  1. Is the study design valid for your question?
  2. Are both inclusion and exclusion criteria described?
  3. Is there an attempt to limit bias in the selection of participant groups?
  4. Are there methodological protocols (i.e. blinding) used to limit other possible bias?
  5. Do the research methods limit the influence of confounding variables?
  6. Are the outcome measures valid for the health condition you are researching?

Critical appraisal of…the Results

  1. Is there a table that describes the subjects’ demographics?
  2. Are the baseline demographics between groups similar?
  3. Are the subjects generalizable to your patient?
  4. Are the statistical tests appropriate for the study design and clinical question?
  5. Are the results presented within the paper?
  6. Are the results statistically significant and how large is the difference between groups?
  7. Is there evidence of significance fishing (i.e. changing statistical tests to ensure significance)?

Critical appraisal of…the Discussion/Conclusion

  1. Do the authors attempt to contextualise non-significant data in an attempt to portray significance? (e.g. talking about findings which had a trend towards significance as if they were significant).
  2. Do the authors acknowledge limitations in the article?
  3. Are there any conflicts of interests noted?

The above checklist is general and should only be used as a quick reference. I would recommend using a checklist specifically to the study design.

The CASP tool has appraisal checklists specifically designed for:

  • Systematic Reviews
  • Randomised Controlled Trials
  • Cohort Studies
  • Case Control Studies
  • Economic Evaluations
  • Diagnostic Studies
  • Qualitative studies and
  • Clinical Prediction Rule. (link below)

Make sure you select the correct CASP Tool for your specific article.

Thanks everyone for reading and I hope this helps. I will see you all in my next blog. Next week the topic is How to conduct a methodological quality assessment when writing a systematic review

See you soon,