Critical appraisal tools

The application of evidence to care is central to the function of nursing. Many uphold that it is no longer acceptable to base nursing on traditional practices and rituals which may be established on false premises or become outdated (Parahoo, 2014; Moule, 2021).

While research sits squarely in the hierarchy of evidence for nursing practice (Polit and Beck, 2020), it is also important for nurses to critically evaluate the application of this evidence to their practice (Parahoo, 2014). 

There are various forms of research and evidence across clinical topics, including:

• meta-analyses and systematic reviews
• randomised controlled trials
• prospective cohort or outcome studies
• case-control studies
• cross-sectional studies
• systematic review of qualitative evidence
• case-reports
• qualitative study
• expert opinion (Ellis, 2023)

Sackett et al (2000) coined the most widely used quote about evidence-based medicine, saying it is:

There are a several approaches to undertaking both quantitative and qualitative research. Quantitative research presents numbers and statistics and is concerned with proof, cause and effect. Qualitative research is concerned with people’s attitudes, beliefs and understandings, and is therefore more concerned with non-numerical data (eg words) (Ellis, 2022).

There are a number of research methodologies and approaches, each with their own requirements, which will inform the approach the nurse takes when assessing the quality of individual pieces of research (Ellis, 2023).

In order to effectively assess research evidence, nurse should have:

• an appropriate critical appraise tool
• at least one research textbook – preferably with a glossary of terms

The first is important in directing the nurse to ask the correct questions of the research and the second enables the nurse to understand the research terms used in the critical appraisal tool.

Some examples of tools which may be used to assess the quality of evidence include:

Critical Appraisal Skills Programme 

This organisation hosts a highly regarded website, where there are a number of checklists which may be used to appraise research, including those for:

• randomised controlled trials
• qualitative studies
• cohort studies
• diagnostic studies
• case-control studies
• systematic reviews

The Joanna Briggs Institute

This international research organisation produces, among other things, critical appraisal tools for various research types including:

• cross sectional studies
• case-control
• case reports
• cohort studies
• qualitative research
• randomised controlled trials
• systematic reviews

There are multiple methods that can be used to critically appraise a piece of evidence, depending on the type of research, the area of research and the purpose for appraisal.

However, there are a series of steps a nurse may follow to ensure they assess the evidence in a structured and holistic way:

1. Identify the type of research to be assessed; the nurse should know:
   • the research type (qualitative or quantitative)
   • the methodology
2. Identify the most appropriate critical appraisal tool:
   • generic qualitative assessment tool are often used for qualitative research
   • the methodology of research (eg randomised controlled trial, cross-sectional study) determines the appraisal tool for quantitative research
3. Review the features of a 'gold standard' version of the research in a research textbook
4. Use the critical appraisal tool or critiquing guide to appraise the evidence by working through the questions identified in it. This will usually mean following a schedule of questions which

Failing to have a working knowledge of how to access, appraise and apply evidence means that nurses will not be fulfilling their professional and ethical obligations to 'practice effectively' using the 'best available evidence' (Nursing and Midwifery Council, 2018). Choosing an inappropriate critical appraisal tool, not understanding the terminology in it or applying the tool incorrectly may cause the nurse to draw incorrect conclusions about the evidence and its applicability to their practice. This, in turn, will lead to suboptimal delivery of care.

Nurses need to have a working understanding of various methods of research in order to be able to identify the paradigm and methodology when reading it. Nurses should also have a working knowledge of some of the terminology used in critiquing various research types so that they can form their own opinion about the usefulness of any evidence they are reading and considering adopting in their practice.

Aveyard H, Greenway K, Parsons L. Beginner's guide to evidence-based practice in health and social care. 4th edn. Maidenhead: Open University Press; 2017

Gray JR, Grove SK. The practice of nursing research: appraisal synthesis and generation of evidence. 9th edn. Philadelphia: Elsevier; 2020

Ellis P. Evidence-based practice in nursing. 5th edn. London: Sage; 2023

Ellis P. Understanding research for nursing students. 5th edn. London: Sage; 2022

Moule P. Making sense of research in nursing and health and social care. 7th edn. London: Sage; 2021. 

Nursing and Midwifery Council. The Code. 2018. https://www.nmc.org.uk/globalassets/sitedocuments/nmc-publications/nmc-code.pdf (accessed 14 November 2023)

Parahoo K. Nursing research: principles, process and issues. 3rd edn. London: Palgrave; 2014

Polit DF, Beck CT. Nursing Research: Generating and Assessing Evidence for Nursing Practice. 11th edn. Philadelphia: Wolters Kluwer/Lippincott Williams and Wilkins; 2020

Sackett DL, Straus SE, Richardson WS et al. Evidence-based medicine: how to practice and teach EBM. 2nd edn. New