An Evidence Pyramid that Facilitates the Finding of Evidence

20 03 2010

Earlier I described that there are so many search- and EBM-pyramids that it is confusing. I described  3 categories of pyramids:

  1. Search Pyramids
  2. Pyramids of EBM-sources
  3. Pyramids of EBM-levels (levels of evidence)

In my courses where I train doctors and medical students how to find evidence quickly, I use a pyramid that is a mixture of 1. and 2. This is a slide from a 2007 course.

This pyramid consists of 4 layers (from top down):

  1. EBM-(evidence based) guidelines.
  2. Synopses & Syntheses*: a synopsis is a summary and critical appraisal of one article, whereas synthesis is a summary and critical appraisal of a topic (which may answer several questions and may cover many articles).
  3. Systematic Reviews (a systematic summary and critical appraisal of original studies) which may or may not include a meta-analysis.
  4. Original Studies.

The upper 3 layers represent “Aggregate Evidence”. This is evidence from secondary sources, that search, summarize and critically appraise original studies (lowest layer of the pyramid).

The layers do not necessarily represent the levels of evidence and should not be confused with Pyramids of EBM-levels (type 3). An Evidence Based guideline can have a lower level of evidence than a good systematic review, for instance.
The present pyramid is only meant to lead the way in the labyrinth of sources. Thus, to speed up to process of searching. The relevance and the quality of evidence should always be checked.

The idea is:

  • The higher the level in the pyramid the less publications it contains (the narrower it becomes)
  • Each level summarizes and critically appraises the underlying levels.

I advice people to try to find aggregate evidence first, thus to drill down (hence the drill in the Figure).

The advantage: faster results, lower number to read (NNR).

During the first courses I gave, I just made a pyramid in Word with the links to the main sources.

Our library ICT department converted it into a HTML document with clickable links.

However, although the pyramid looked quite complex, not all main evidence sources were included. Plus some sources belong to different layers. The Trip Database for instance searches sources from all layers.

Our ICT-department came up with a much better looking and better functioning 3-D pyramid, with databases like TRIP in the sidebar.

Moving the  mouse over a pyramid layer invokes a pop-up with links to the databases belonging to that layer.

Furthermore the sources included in the pyramid differ per specialty. So for the department Gynecology we include POPLINE and MIDIRS in the lowest layer, and the RCOG and NVOG (Dutch) guidelines in the EBM-guidelines layer.

Together my colleagues and I decide whether a source is evidence based (we don’t include UpToDate for instance) and where it  belongs. Each clinical librarian (we all serve different departments) then decides which databases to include. Clients can give suggestions.

Below is a short You Tube video showing how this pyramid can be used. Because of the rather poor quality, the video is best to be viewed in full screen mode.
I have no audio (yet), so in short this is what you see:

Made with Screenr:  http://screenr.com/8kg

The pyramid is highly appreciated by our clients and students.

But it is just a start. My dream is to visualize the entire pathway from question to PICO, checklists, FAQs and database of results per type of question/reason for searching (fast question, background question, CAT etc.).

I’m just waiting for someone to fulfill the technical part of this dream.

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*Note that there may be different definitions as well. The top layers in the 5S pyramid of Bryan Hayes are defined as follows: syntheses & synopses (succinct descriptions of selected individual studies or systematic reviews, such as those found in the evidence-based journals), summaries, which integrate best available evidence from the lower layers to develop practice guidelines based on a full range of evidence (e.g. Clinical Evidence, National Guidelines Clearinghouse), and at the peak of the model, systems, in which the individual patient’s characteristics are automatically linked to the current best evidence that matches the patient’s specific circumstances and the clinician is provided with key aspects of management (e.g., computerised decision support systems).

Begin with the richest source of aggregate (pre-filtered) evidence and decline in order to to decrease the number needed to read: there are less EBM guidelines than there are Systematic Reviews and (certainly) individual papers.
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A milestone for TRIP

13 04 2008

WE MADE IT!” EXULTED JON BRASSEY FROM THE TURNING EVIDENCE INTO PRACTICE (TRIP) DATABASE ON HIS BLOG.

IN MARCH TRIP WAS SEARCHED MORE THAN ONE MILLION TIMES! A MILESTONE IN THE HISTORY OF TRIP.

The TRIP-database is a search engine that simultaneously searches many sources. Its primary focus is to help clinicians identify the best available evidence to answer their clinical questions.

In my first Evidence Based Searching Classes (2006) I advocated TRIP as a major tool to search for clinical evidence (next to National Guideline Clearinghouse, the Cochrane Library and PubMed). Although most clinicians recognized its value, they didn’t use it regularly in daily practice, as only the first 3-5 monthly search commands were for free. Since TRIP switched to free access in September 2006, its usage grew enormously. On a worldwide basis, searches increased from around 25,-30,000 to several hundred thousands per month (isn’t that a factor 30-40?) .

Good that TRIP has made it through the transition from a subscription to a free access service. Not only for TRIP, but even more so for its users. Ideally, evidence should be freely available to everyone, shouldn’t it?!

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Afgelopen maand heeft TRIP een mijlpaal bereikt: 1 miljoen (be)zoekers!

DeTurning Evidence into Practice (TRIP) database is een zoekmachine, ook wel grazer genoemd, die verschillende databases simultaan doorzoekt. De nadruk ligt vooral op evidence based clinical practice. Met TRIP willen de makers bereiken dat artsen makkelijker een goed -evidence based- antwoord vinden op hun vraag. Een aantal jaar was TRIP slechts tegen betaling te raadplegen. Sinds dat Jon en collega’s de overstap hebben gewaagd van betalende naar gratis service is het aantal bezoekers drastisch gestegen, tot de climax van 1 miljoen (be)zoekers in maart.