It seems that an examination of clinical practice guidelines while chanting the mantra of evidence-based medicine could provide endless fodder for your recently initiated Controversy section. Kenneth Marshall's contribution1 on one of the Canadian Diabetes Association's guidelines,2 in which all recommendations have been carefully rated according to the available evidence, demonstrates how easy it is to fuel such a discussion.
Marshall,1 and Hertzel Gerstein and Sara Meltzer in their reply,3 cite the UK Prospective Diabetes Study4 as a critical trial. Marshall failed to recognize that the population recruited to this study reflects those who would be identified by a "screening" process (i.e., patients with newly diagnosed diabetes). They were subsequently managed in a very practical fashion that is replicated daily in physicians' offices and diabetes centres. Furthermore, the trial demonstrates the insidious progression of glucose intolerance with time, suggesting a potential benefit of early intervention. Glycemic control deteriorated in the UK Prospective Diabetes Study, even in patients in the intensive treatment policy group, whose glycosylated hemoglobin level had returned to pretreatment values by 6 years, yet a clear difference in the rate of microvascular complications still emerged. Treatment strategies were constrained by the goals of the study to examine effects of diabetes monotherapy until marked hyperglycemia developed. Surely a "ray of hope," to borrow Marshall's phrase, is the possibility that better control than this can lead to even greater reductions in complication rates. The effects of antihypertensive therapy in these newly diagnosed patients were equally impressive.5
Labelling an individual as having diabetes undoubtedly has adverse psychological potential that we should attempt to avoid. An enlightened approach to patient education, based on the accepted interpretation of clinical trial results for glycemic control, lipid-lowering and antihypertensive therapies in diabetes, should help to bring a more positive attitude to the diagnosis. Marshall's harsh denial that these therapies can improve the quality of life for a person diagnosed with diabetes is unjust, as is his unsupported contention that "screening will do a great deal of harm."
In our practice of medicine we remain in a state of overall evidence deficit. Taking a nihilistic approach while waiting for this deficit to be completely remedied hampers the progress of clinical research and the process of patient care. The Canadian Diabetes Association's guidelines recognize this with their careful rating of evidence to support recommendations.