Information overload is a major barrier in finding that particular medical information you’re really looking for. Search- and EBM-pyramids are designed as a (search) guidance both for physicians, med students and information specialists. Pyramids can be very handy to get a quick overview of which sources to use and which evidence to look for in which order.
But look at the small collection of pyramids I retrieved from Internet plus the ones I made myself (8,9)………
What may be particularly confusing is that these pyramids serve different goals. As pyramids look alike (they are all pyramids) this may not be directly obvious.
There are 3 main kinds of pyramids (or hierarchies):
- Search Pyramid (no true example, 4, 5 and 6 come closest)
Guiding searches to answer a clinical question as promptly as possible. Begin with the easiest/richest source, for instance UpToDate, Harrison’s (books), local hospital protocols or useful websites. Search aggregate evidence respectively the best original studies if answer isn’t found or doubtful.
- Pyramid of EBM-sources (3 ,4, 8 )
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.
- Pyramid of EBM-levels (1, 2, 5, 7, 9)
Begin to look for the original papers with the highest level of evidence.
Often only individual papers/original research, including Systematic Reviews, are considered (1, 9), but sometimes the pyramid is a mixture of original and aggregated literature (2,5)
- A mixture of 2, 3 and/or 4 (2,5)
- Some place Cochrane Systematic Reviews higher than ‘other systematic reviews’, others place meta-analysis above Systematic reviews (2,6). This is respectively unnecessary or wrong. (Come back to that in another post).
- Sometimes Systematic reviews are on top, sometimes Systems (never found out what that is), sometimes meta-analysis or Evidence based Guidelines
- Synopses (critically appraised individual articles) may be placed above or below Syntheses (critically appraised topics).
- Textbooks and Reviews may at the base of the pyramid or a little more up.
- Evidence Summaries ?= Summaries of the evidence? = Evidence Syntheses? = critically appraised topics?
- DARE is considered a review, but it is really a synopsis (critical appraised summary) of a Systematic Review.
Isn’t it about time to weed the pyramids rigorously?
Are pyramids really serving the aim of making it easier for the meds to find their information?
Like to hear your thoughts about this.
What my thoughts are? I will give a hint: I would rather guide the informationseeker through different routes, dependent on his background, question, available time and goal. The pyramid of evidence sources and the levels of evidence would just be part of that scheme, ideally.
Will be continued….