What Does “Critical Appraisal” Mean in Evidence-Based Practice?

Critical appraisal: Examining each piece of a research study

Critical appraisal: Focusing in on each section of a research study to determine validity, importance, and application to practice.
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Evidence-based practice (EBP) is the deliberate use of the best evidence that is tempered with your clinical expertise and the patient’s preferences and clinical situation.

EVERY nurse is responsible for practicing according to the best evidence and research findings – therefore, every nurse needs to understand WHAT EBP is, HOW to decide if the evidence is valid and significant (that is, how to perform and interpret a critical appraisal), HOW to decide if your patient may benefit from the evidence, and WHEN to translate evidence into practice changes. 

In this post, I’ll describe the overall purpose of performing a critical appraisal of research and evidence-based literature and introduce you to the basic steps of critical appraisal.

And if you haven’t downloaded this yet, my free Evidence-Based Practice cheat sheet includes an intro to EBP and the major questions you need to ask when performing a critical appraisal. I’ll provide more details about the major questions in the rest of the posts for this month. Download the cheat sheet and follow along!

A critical appraisal is basically a detailed examination of published research for the purpose of making a decision about scientific merit and, therefore, for making a decision about use of the evidence in practice.

What is a Critical Appraisal?

Critical appraisal is also known as a research or evidence critique. Critiquing the literature, appraising the literature, or critically evaluating the literature are phrases that refer to a deliberate examination of a published research study and making a judgment as to the validity of its methods, importance of the question and results, and application to practice. 

A critical appraisal is basically a detailed examination of published research for the purpose of making a decision about scientific merit.

Why is evaluating scientific merit important? Because you only want to use research findings in practice that are generated from valid research methods. 

How will you know if the study was worth doing if you don’t examine the research question for clinical and practical importance? How will you know if the study is valid if you don’t examine the research methods? How will you know the study is important if you don’t examine the magnitude and significance of the findings? Once you are satisfied that the study was necessary, valid, and important — then you can determine whether your patient or target population could benefit from the study findings. 

To get the answers to these questions, you need to do a critical appraisal of your selected research study. 

An Intro to Critical Appraisal Steps

There are several basic steps in performing a critical appraisal.

First, you need a critical appraisal tool. Every nursing research text I’ve ever read provides questions to ask when appraising a research study — quantitative or qualitative. You can use these questions as a critiquing guide and write the answers out on a sheet of paper. When you complete the critique, you can review the answers and come up with your evaluation of the study. 

While this method works, it is not as conducive to coming up with an overall answer to the question, “Should I trust that the results of this study are valid and important?” as having a tool to guide you to the answers you need. And guess what? These critical appraisal tools are available!

The Centre for Evidence-Based Practice is one of my favorite EBP sites. They have some basic EBP appraisal sheets for diagnostic studies, systematic reviews, prognostic studies, and randomized controlled trials (RCTs) that are available in English, German, Chinese, Lithuanian, Portuguese, and Spanish. They were originally written for physicians and are written using research language. I used these, and ones from other EBP sites, to create critical appraisal sheets for students in my applied EBP class. Once I finish updating these tools, I’ll make them available.

The first tool I developed was one that I used for a research journal club I started for my nursing research students. It is a one-page, two-sided tool that I used for students to critique both quantitative and qualitative studies. I wrote about the tool and published it in an article in Nursing Education in Practice (Thompson, 2006). I shared this tool when I was a faculty liaison to the Evidence-Based Practice Council of a local hospital system; they have used and revised it over the years. I’m working on some revisions, but until I get that done, if you are interested in using this for your own critiques, please refer to the article. The full citation is in the Reference list at the end of this post. 

Four Major Questions to Ask When Critically Appraising a Study

These are the major questions to ask for each study you are appraising. The answers to these questions will help you determine if the study is worth reading and if the results can be used in clinical or professional practice.

What follows is just a short synopsis of the steps: I’ll go into greater detail in the coming weeks. 

Is the Research Study Necessary?

The first question to ask revolves around the Research Problem and Purpose of the study. You want to determine whether the author has made a good case for why the research study needed to be conducted. Are the research question/hypotheses and purpose clear? Is the study significant to practice?

Look for the problem statement and then the evidence for why the stated problem is really a problem! If you find this evidence, then continue to the next question. But if the problem and purpose are not clear or the reasons aren’t compelling … you can stop reading the study. Go find a study that is relevant and start again!

Are the Results Valid (i.e., Are the Study Methods Strong/Rigorous?)

To figure out if the research results are valid, you need to examine the research methodology! Examining the research methodology means basically questioning every choice the researcher made in conducting the study (that they published).

You are looking for internal consistency between the quantitative or qualitative research design and the researcher’s choices. For example, for RCTs you’d want to find answers to: what specific type of trial design was used? how were the subjects chosen? what was the sample size? were the subjects randomized? were the subjects similar at the start of the study? was the attrition rate acceptable? was an intention-to-treat analysis performed? were the research instruments valid and reliable? etc. 

This question is at the heart of critical appraisal because if the study methods are not valid, then you CANNOT BELIEVE THE RESULTS! That’s right, I shouted that.

One of my “aha” moments came when I was reading Dr. Trisha Greenhalgh’s book, How to Read a Paper. I highly recommend this text. 

Dr. Greenhalgh wrote something that I’ve never forgotten and that I drill into my EBP students — Read the Methods First! 

If the methods are suspect, you CANNOT BELIEVE the results and, therefore, should not waste your time reading the rest of the paper. Go find another study!

Are the Research Results/Findings Important?

If you’ve decided that the research methods are valid, then you can continue to read the study. At this point you want to look at the actual results or findings. So that means looking at the quantitative (numbers/stats) or qualitative findings (e.g., themes or theory).

For quantitative results, what is the relative risk, absolute risk, risk reduction, odds ratio, likelihood ratio, hazard ratio — whatever is appropriate for the type of study conducted. You want to evaluate the magnitude of the result (how big) and the significance of the result (statistical and clinical significance). 

For qualitative findings, you want to reflect on the themes that the researcher identified from the participant data. Do the themes make sense with what the researcher reported about the participants? Do the themes make sense with the data? In other words, are the qualitative findings reliable and valid?

If the study was necessary, the methods strong, and the results statistically and clinically significant, then you can make a decision about how to translate the findings into your professional or advanced nursing practice. 

Can I Apply the Results to My Patient or Patient’s Situation?

This is the ultimate question, isn’t it? How do we translate research and evidence into practice so that it will benefit our patient? 

You shouldn’t just use the research results or study findings on any patient. You first want to decide if your patient is similar to the sample used in the study. Look at the age range of the sample population, disease state, comorbidities, health status, etc. If your patient is NOT similar to the study sample, you can’t be confident that the treatment will perform in the manner described in the study article. 

If your patient is a good match for the study sample, then you have to decide if the treatment will be acceptable or feasible in your particular practice setting. Not all settings will have the resources, or inclination, to treat the patients with evidence from the newest study. 

Before talking with the healthcare team and the patient, the last consideration is whether the benefits of the new treatment will outweigh the potential risks or harms to the patient. 

 

You should get in a habit of asking a lot of questions (to yourself) when reading the research literature. In the following weeks, I’ll give you more details and do a deep dive on the specifics on these major questions.

How to Cite this Blogpost in APA*:

 

Thompson, C. J. (2017, November 7). What does “critical appraisal” mean in evidence-based practice? [Blogpost]. Retrieved from https://nursingeducationexpert.com/critical-appraisal *Citation should have hanging indent

References

Greenhalgh, T. (2014). How to read a paper: The basics of evidence-based medicine (5th ed.). Oxford, UK: Wiley Blackwell/BMJ Books.

Thompson, C. J. (2006). Fostering skills for evidence-based practice: The student journal club. Nurse Education in Practice, 6(2), 69-77.