Finding Empirical Evidence: B: Hierarchy of evidence

Editor's Notes

• #2: Show of hands. Who feels confident with their understanding of the hierarchy of evidence and how to find research at different levels of evidence?
• #3: There is so much medical literature published you need to know how it is organised and the quickest way to find the information you need. In Medical research it is particularly important to you are familiar with notions of evidenced based practice – that you base your practice decisions on the most up to date and high quality research on the population focus group you are working with in order to determine the best treatment. Click link to OneSearch record of this eBook (will need Pheme credentials to read it), also shows the Multiple Versions feature. Show contents and discuss briefly use of ebook platforms and of bookshelf. Look at contents.. Focus particularly on break down of how to assess different papers that evaluate particular studies and in particular systematic reviews and guidelines. Ask if students are familiar systematic reviews and Evidence based guidelines (hands up) and then to discuss some of the differences between them? Ask for feedback on these? Greenhalgh, Trisha. 2014. How to read a paper: the basics of evidence-based medicine. BMJ Books: Hoboken.)
• #4: “The term ‘level of evidence’ refers to what degree that information can be trusted based on study design”. (Greenhalgh 2014) As you can see from this pyramid the higher the corroboration of different types of evidence, the higher it is on the hierarchy. You will come across many different forms of the hierarchy as it is continually being contested and evolving – so you will have to get used to interpreting it at a critical level. This is the pyramid at its most basic level.. With single studies being considered the least reliable, moving to systematic reviews that undertake a robust review of studies undertaken on specific interventions, through to evidence based guidelines.. (however need to question if these latter do belong at the top of the hierarchy – in trying to provide an overview of current best practice of a condition as a whole) We don’t have access to decision support systems at this time. They are systems that directly link to patient records. Do have a EBM Lib Guide that provides links to the resources we offer to support EBM.
• #5: The bottom layer of the main hierarchy – single studies – has its own hierarchy depending on the original type of study performed. This is where – if you are doing your own literature search or systematic review of treatment/disease research for a specific cohort – you would need to critically assess the research/studies/case focus for their research vigour and relevance to your area of health and cohort. For single studies RCT are considered the most robust and unbiased and they are often the focus on systematic reviews.
• #6: Here is a new revised pyramid, (Developed by Dr Murad and his team at the Evidence Based Practice Centre, Mayo Clinic in Rochester USA.) to take into account the need to think critically about the design and development of individual studies – replacing a straight line with a wavy one to indicate that some research lower down the hierarchy may actually be better if designed better than RCTs. The separation of systematic reviews from the pyramid emphasises that they themselves are a filter through which evidence is viewed and also subject to critical review in their overall design and development. The studies into your specific intervention or research focus area need to be available in order to undertake a systematic review. The proposed new evidence-based medicine pyramid. (A) The traditional pyramid. (B) Revising the pyramid: (1) lines separating the study designs become wavy (Grading of Recommendations Assessment, Development and Evaluation), (2) systematic reviews are ‘chopped off’ the pyramid. (C) The revised pyramid: systematic reviews are a lens through which evidence is viewed (applied).
• #7: This pyramid represents the hierarchy of evidence that can be used to answer clinical questions. It will help lead you to the best resources where you can find evidence for your question. The higher the level of evidence (clinical importance) the less information out there for you to find. Higher levels of evidence are problem focused. In your exploration of EBP and hierarchies of evidence you may come across slightly different hierarchies, this is the UWA FMDHS endorsed hierarchy of evidence.
• #8: Middle level: Systematic Reviews. Systematic reviews analyse and appraise primary studies on the same question. This is a simplified version of the process. (There are UWA as a well as a number of resources for this) The final report will include their search strategies, keywords, subject headings. It is good to look at this to enhance your own learning/searching on your topic. Finding a systematic review on a topic can save you a lot of time. A well structured systematic review will include the databases searched, search strategies used and a detailed analysis of studies included in the review – their quality and strengths, can see also the reasons why certain studies were excluded or considered questionable.
• #9: One consideration in the evaluation of evidence is who has produced it and how good their methodology is? One of the key highly reputed players in Australia is The Joanna Briggs Institute who collaborate with Australian and international research institutes to produce systematic reviews and from these best practice guidelines available through their library JBI Connect. They also produce methodology guides and software to support critical appraisal. This link is a good one for quick checklists on how to appraise different types of studies as well as systematic reviews.
• #10: One of the most robust and trusted producers of systematic reviews is the Cochrane Collaboration. Because systematic reviews have traditionally been built on RCT’s they have Cochrane Central which aims to bring together all randomized controlled trials from core databases such as Medline and Embase and from other sources. The Cochrane Reviews (like JBI) also work in collaboration with International research bodies to produce systematic reviews and have a number of specialist resource databases such as their SR Database and database of Randomised control trials. Like JBI they also produce and collate methodology reviews and critical appraisal of research tools which have been collated into a number of Handbooks. This link is a good one for quick checklists on how to appraise different types of studies as well as systematic reviews.
• #11: The top levels This section of the literature will become important later in your course when you begin clinical practice. Can you trust the synthesis of the evidence that has been completed – who has been involved in it, how recent? Is it comprehensive and based on appraised high level studies and systematic reviews or in providing a comprehensive overview of current best practice is it compromised. http://ebm.bmj.com/content/21/4/121.full Pyramids are Guides not rules: the evolution of the evidence pyramid.
• #12: These are the key databases where you can find studies and systematic reviews, guidelines and individual studies See our guide for access to them: Resources for Answering Clinical Questions: http://guides.is.uwa.edu.au/ACQresources?hs=a Go to this site and And Dentistry – EBM tab http://guides.is.uwa.edu.au/c.php?g=324873&p=2177834 We will be looking at some of these in more detail in the upcoming workshop. Take a bit of stretch and break now or have a look at the websites of the Joanna Briggs Institute or Cochrane Collaboration or our LibGuide link here.
• #13: Shown them how to navigate to this Guide from the UWA website. Library’s guide to resources for answering clinical questions. The second tab in the guide that you can see here lists EBP resources available through the library catalogue, and tells which level of evidence you will find within. You can see a table of different resources we have, and the level of evidence you can find in each. The green button next to each connects to a database-specific guide that lists tips for searching, tips on how to broaden or narrow your search, the best clinical use of the information, and positives and negatives of that particular resource. Includes tips on how to broaden your search and how to narrow your search, and tips on using truncation and wildcards.