World Gastroenterology Organisation (WGO) - Global Guardian of Digestive Health. Serving the World.

Graded Evidence

WGO's 'Graded Evidence' system is built to help National Societies of Gastroenterology and all those interested in the practice and research of gastroenterology keep track of the literature in topics covered by WGO Guidelines. Most guidelines are based on evidence which is out of date as they appear. Sometimes the 'lag time' is as much as 3–4 years. WGO's Graded Evidence system bridges this gap. WGO Guidelines are constantly reviewed and updates are built when new information becomes available.

Evidence is classified into three categories:

  • Systematic reviews, consensus statements, meta-analyses, evidence-based practice guidelines
  • Clinical trials
  • Other reading

Professor André Elewaut

WGO is honoured to have been able to enlist the expertise and assistance of Prof. André Elewaut in the grading of evidence to support practice guidelines. Each citation is assessed by a specialist in terms of the quality of an article and how relevant it is for the guideline topic in question. Articles are then scored by assigning one or several stars:

  • Grade Key
  • Key Development
  • Very Important
  • Important
  • Special Mention

The following journals are scanned for new evidence:

Rank /Impact factor Name Journal Publisher
 
1 Gastroenterology W.B. Saunders Company
2 Annals of Internal Medecine Am. College of Physicians
3 Hepatology W.B. Saunders Company
4 GUT BMJ Publishing Group
5 Journal of Hepatology Elsevier Science B.V.
6 Alim. pharmacology & therapeutics Blackwell Science Ltd
7 American Journal of Gastroenterology Elsevier Science B.V.
8 Inflammatory Bowel Disease Lippincott Williams & Wilkins
9 Gastrointestinal Endoscopy Mosby Inc.
10 J. of Pediatric Gastroenterology & Nutrition Lippincott Williams & Wilkins
11 Digestion S. Karger AG
12 Scandinavian Journal of Gastroenterology Taylor and Francis A.S.
13 Eur. J. of Gastroenterology and Hep. Lippincott Williams & Wilkins
14 Digestive Diseases and Sciences Kluwer Acad./Plenum Publ.
15 Endoscopy Georg Thieme Verlag
16 J. of Gastroenterology and Hepatology Blackwell Science Asia
17 Digestive Surgery S. Karger A.G.
18 Digestive Diseases S. Karger A.G.

Coverage

Graded Evidence is an iterative process - and for that reason need not be so concerned with searching both Medline, Embase and Biosis for example. All top GI journals are covered by both Medline and Embase and in single one-off complex searches unique citations in one or the other are often due either to differences in database currency or differences in coverage of less important journals. In addition to cost issues, the generous republishing and copyright policies of the US National Library of Medicine (NLM) make Medline the preferred choice.The WGO Graded Evidence library is grateful to the NLM for making data available to clinicians and practitioners outside the US for free.

Search Strategies

Search strategies for each topic are based on a combination of controlled access and free text terms. The strategies aim for 'precision rather than 'sensitivity'. Highly sensitive search strategies as for example used by the Cochrane Collaboration when collecting literature reviews produce many irrelevant records. The advantage is these strategies retrieve all records which are relevant to a topic. But the 'number needed to read' is large and thus time consuming. Busy gastroenterologist probably prefer very precise search strategies in top GI journals and thus make sure every major article is found. The WGO Graded Evidence works along the lines of PUBMED Medline 'Clinical queries' features. Precise searches only find relevant information. Indexing errors may still be responsible for irrelevant or duplicate records. Case studies and animal studies are not usually included.

Finding Evidence

True evidence-based searches require a deeper understanding of databases and search strategies not necessary for our purpose. WGO Global Guidelines are not systematic reviews. The WGO Library adheres to the Cochrane Collaboration's views that a searcher has to work through a hierarchy of evidence as follows:

As you move down the hierarchy you are more likely to find 'opinion' instead of evidence. For a more complete search on a topic please consult also:

Graded Evidence records link directly to Pubmed-Medline and from here the searcher can follow the various link options to find similar records or an indication of how to find full text.

Please consult WGO's Ask a Librarian (AAL) system to request specific help with search strategies or your individual search requirements. The AAL service is free to all gastroenterologists in 'developing nations'. Let us know how we can improve our Graded Evidence system by sending us any evidence we may not have included in our listings for that topic.

Contact Us