Evaluation of Guideline Recommendations on Oral Medications for Type 2 Diabetes Mellitus

Background: Clinical practice guidelines have an important role in guiding choices among the numerous medications available to treat type 2 diabetes mellitus, but little is known about their quality. Purpose: To assess whether guidelines on oral medications for type 2 diabetes are consistent with a systematic review of the current evidence and whether the consistency of the guidelines depends on the quality of guideline development. Data Sources: MEDLINE, CINAHL, and guideline-specific databases were searched between July 2007 and August 2011, after the 2007 publication of a peer-reviewed systematic review on oral diabetes medications. Study Selection: Two reviewers independently screened citations to identify English-language guidelines on oral medications to treat type 2 diabetes that were applied in the United States, United Kingdom, and Canada. Data Extraction: Reviewers assessed whether the guidelines addressed and agreed with 7 evidence-based conclusions from the 2007 systematic review. Two reviewers independently rated guideline quality by using 2 domains from the Appraisal of Guidelines Research and Evaluation instrument. Data Synthesis: Of the 1000 screened citations, 11 guidelines met the inclusion criteria. Seven guidelines agreed with the conclusion that metformin is favored as the first-line agent. Ten guidelines agreed that thiazolidinediones are associated with higher rates of edema and congestive heart failure compared with other oral medications to treat type 2 diabetes. One guideline addressed no evidence-based conclusions, and 5 guidelines agreed with all 7 conclusions. The summary scores of the rigor of development (median, 28.6% [range, 16.7% to 100.0%]) and editorial independence (median, 75.0% [range, 8.3% to 100.0%]) domains varied greatly across guidelines. Guidelines that received higher quality scores contained more recommendations that were consistent with the evidence-based conclusions. Limitation: Only English-language guidelines targeting users in the United States, United Kingdom, and Canada that contained recommendations on oral medications were included. Conclusion: Not all practice guidelines on oral treatment of type 2 diabetes were consistent with available evidence from a systematic review. Guidelines judged to be of higher quality contained more recommendations consistent with evidence-based conclusions. The quality of guideline development processes varied substantially.