What is Critical Appraisal?

""Once you have asked the clinical question and searched for evidence, Assessment 2 asks you to critically appraise the evidence you have found.  This is a really important process because it allows you to:

  • cut down on information overload,
  • disregard studies which have scientific flaws, and
  • find studies relevant to your situation.

In the Evidence-Based Practice process, and especially in the process of evaluating primary research, we need to go beyond the usual CRAP test to also critically appraise certain aspects of the evidence. Even when we have found a study addresses our keywords and concepts, certain questions need to be addressed, especially:

  • Is the study relevant to our clinical question?
  • How well (scientifically) was the study done, especially taking care to eliminate bias?
  • What do the results mean and are they statistically valid (and not just due to chance)?

Introduction to Critical Appraisal

More Resources

Video

EBook

EBook Chapter

  • Critically appraise the evidence - Part 2: EBP Step 3 in the eBook by Glasziou, Salisbury, & Del Mar quoted above. Includes an example of critical appraisal of a real RCT into the use of elastic stockings to prevent deep-vein thrombosis (DVT) on long aeroplane flights.

Critical Appraisal Tools

You have been asked in Assessment 2 to use a critical appraisal tool to critically appraise each of the research papers you have identified. Here are some commonly used tools:

Quick appraisal

When deciding whether to include a study in your results, it is worth checking some of these factors.

  • Relevance - It's easy to do this by comparing the PICO used in the study to the PICO of your clinical question. Is it close enough to make the results relevant?
  • Bias - "Bias is the degree to which the result is skewed away from the truth" . Bias can occur in many ways, and can occur in the selection of subjects for study, allocation to groups, and measurement of results, but the best way to prevent it is to keep details of interventions hidden from participants and also researchers (Glasziou, Salisbury, & Del Mar, 2007, p. 75). This is called blinding. How much is this study prone to bias?
  • Confounding factors - "Confounding factors are patient features and other possible causal factors, apart from the one that is being measured, that can affect the outcome of the study." These can be eliminated or reduced by ensuring that groups are matched as closely as possible at the start of the study, and managed in the same way in the course of the study (Glasziou et al., 2007, p. 76).
  • Trustworthiness - the RAMMbo mnemonic can help you to work out how trustworthy a study is:
R Recruitment Were the subjects in the study representative of the target population? Were there enough subjects to make the study valid?
A Allocation Were the subjects randomly (and "blindly") allocated to groups?
M Maintenance Was the status of the study group and the control group maintained throughout the trial? Were they treated the same way apart from the intervention?
Mbo Measurement (blinding, objective measures) Were the subjects (and researchers) blinded to the intervention and were the outcomes measured objectively?  Was bias eliminated as much as possible?

Source: Glasziou, P., Del Mar, C., & Salisbury, J. (2009). Evidence-based practice workbook: Bridging the gap between health care research and practice (2nd ed.). Retrieved from ProQuest Ebook Central