The Guideline Elements Model (GEM) was first developed in 2000 to store and organize the heterogeneous knowledge and information contained in clinical practice guidelines. GEM provides an intermediate knowledge representation that permits natural language guidelines to be translated into a format that can be processed by computers. GEM uses XML to describe a comprehensive set of pertinent concepts, relationships between concepts, and attributes. The resulting guideline representation can be used for multiple purposes including incorporation into decision support systems, electronic guideline distribution, and guideline querying. The GEM Cutter editor was designed to facilitate markup of guideline text and to facilitate its translation into XML. It was intended for an array of guidelines users including developers, disseminators, implementers, quality appraisers, and end users.

In June 2010, with the assistance of a medical librarian, we conducted a literature search using three databases: PubMed, SCOPUS, and ISI Web of Knowledge. Search terms used were: ‘GEM AND guideline elements model’ which resulted in 54 articles (see Figure 1). To further expand our search we used the original publication in which GEM was described (1), and searched for articles with related citations, or articles in which the original paper was referenced. Non-English journals were excluded. This expanded search resulted in 322 articles. After eliminating duplicates, 159 articles remained. Because of our interest in diffusion of the model, the 12 articles that were authored by Yale Center for Medical Informatics (YCMI) collaborators were set aside to be analyzed separately. Of the 147 remaining articles 59 could not be accessed (i.e., articles that were not electronically retrievable as full texts or available locally) and 38 articles were not about GEM, i.e. GEM was not mentioned in the text or referenced in the bibliography (e.g., geology articles). This resulted in a final list of 50 articles which were analyzed by all the authors (Figure 1). Articles were categorized according to subject matter and critiques of GEM were extracted for further analysis (Table 2). We reviewed a sample of 20 papers to help define categories of how GEM was being used. These subject categories were iteratively refined dependent upon major categories identified in the 20 papers, and continuously evalulated as the remaining articles were reviewed.

The Guideline Elements Model was used or referenced in 50 manuscripts arising from 8 countries: Italy, Israel, Canada, Australia, France, Sweden, Austria and the United States. Review of the website registry of GEM Cutter downloads revealed 563 incident downloads since 2006 (see Table 1), suggesting that GEM has been applied by many users beyond those who have published their work.

GEM has been praised as “the leader” in the document-centered approach to guideline knowledge representation (3). In contrast to the model-centered approach to guideline formalization—a conceptual model in which the relationship between the original document and the model is only indirect—the document-centered approach takes the original guideline text as a starting point and constrains the translation process toward congruence with the source knowledge.

As GEM approaches the end of its first decade of use, we note that the Guideline Elements Model has been applied for a wide variety of purposes and achieved mention in a substantial number of research reports. We presume that there have been additional uses that have not resulted in publication, as suggested by the 921 downloads of GEM Cutter.