Evaluation of guideline recommendations on oral medications for type 2 diabetes mellitus: a systematic review

Ann Intern Med. 2012 Jan 3;156(1 Pt 1):27-36. doi: 10.7326/0003-4819-156-1-201201030-00005.


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.

Primary funding source: Agency for Healthcare Research and Quality.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review
  • Systematic Review

MeSH terms

  • Canada
  • Diabetes Mellitus, Type 2 / drug therapy*
  • Evidence-Based Medicine
  • Humans
  • Hypoglycemic Agents / adverse effects
  • Hypoglycemic Agents / therapeutic use*
  • Metformin / adverse effects
  • Metformin / therapeutic use*
  • Practice Guidelines as Topic / standards*
  • Thiazolidinediones / adverse effects
  • Thiazolidinediones / therapeutic use*
  • United Kingdom
  • United States


  • Hypoglycemic Agents
  • Thiazolidinediones
  • Metformin