The evidence-based Canadian Diabetes Association (CDA) 2008 clinical practice guidelines for the prevention and treatment of diabetes in Canada (1) differ from the consensus statement by Nathan et al. (2), although both were published virtually at the same time. The consensus statement, which represents the authors’ collective analysis, evaluation, and opinion, is said not to represent official association opinion, yet it is listed as a consensus statement of the American Diabetes Association and the European Association for the Study of Diabetes. In contrast, the CDA clinical practice guidelines do represent the CDA's official position. The CDA clinical practice guidelines follow the AGREE (Appraisal of Guidelines for Research and Evaluation) instrument (3) and have a standardized evidence-based approach to all recommendations, with over 90 authors and a steering committee of 18, and all recommendations need 100% approval by the steering committee and the chapter authors. This removes as much bias as possible. The ADA/EASD consensus group consists of seven authors and emphasizes their “collective knowledge and clinical experience, which takes into account benefits, risks, and costs.” Neither publication specifically provides a cost analysis. We believe cost analyses are generally inconsistent in methodology and lack assessment of hypoglycemia and quality of life and therefore have been omitted from the consensus analysis.
The algorithms differ in the choice of medications to prescribe when metformin fails to control hyperglycemia. As opposed to the consensus statement, which has a two-tier system, the CDA guidelines give equal weight to the following classes of medications available in Canada (alphabetically listed): α-glucosidase inhibitors, DPP-4 inhibitors, insulin, insulin secretagogues, thiazolidinediones, and weight-loss agents. We find the two-tier approach to be concerning, as it includes only basal insulin and sulfonylureas as preferred choices. Our committee believes that patients and practitioners deserve more choice.
Nathan et al. (2) state that they take costs into account, but they do not factor in self-monitoring of blood glucose in their algorithm. The consensus statement also does not recommend glyburide, which is likely the least expensive sulfonylurea, and further states that sulfonylureas should be discontinued altogether when insulin is used. Therefore, when basal insulin is used with an intermediate-acting insulin, it is very likely that more than one injection will be required.
With regard to thiazolidinediones, we do not find that there is cause to exclude rosiglitazone based on recent evidence from the ACCORD (Action to Control Cardiovascular Risk in Diabetes), RECORD (Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes), and Veterans Affairs Diabetes trials (4,5,6), which do not show an increased risk of myocardial infarction. Moreover, these trials are specifically designed to help address this question, as opposed to the studies quoted in the consensus statement.
In summary, both views have merits but differ in important ways. The CDA evidence-based approach gives more flexibility, whereas the consensus approach is more directive and opinion based.
APPENDIX
Members of the CDA 2008 Clinical Practice Guidelines Steering Committee: Lori Berard, Gillian Booth, Sarah Capes, Alice Y.Y. Cheng, Maureen Clement, Keith Dawson, Amir Hanna, William Harper, Stewart B. Harris, Robyn Houlden, Dereck Hunt, Helen Jones, Margaret L. Lawson, Lawrence A. Leiter, David M. Thompson, Ehud Ur, and Jean-François Yale.
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References
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