Diabetes Screening in Canada (DIASCAN) Study: prevalence of undiagnosed diabetes and glucose intolerance in family physician offices.

OBJECTIVE To assess the prevalence of undiagnosed diabetes and glucose intolerance in individuals > or =40 years of age who contacted their family physician for routine care. RESEARCH DESIGN AND METHODS The study used a stratified randomized selection of family physicians across Canada that was proportional to provincial and urban/rural populations based on Statistics Canada Census data (1996). Consecutive patients > or =40 years of age were screened for diabetes. If a casual fingerprick blood glucose was >5.5 mmol/l, the patient returned for a fasting venous blood glucose test. If the fasting blood glucose was 6.1-6.9 mmol/l, a 2-h 75-g post-glucose load venous blood glucose was obtained. Results of these tests were used to classify patients in diagnostic categories. RESULTS Data were available for 9,042 patients. Previously undiagnosed diabetes was discovered in 2.2% of the patients, and new glucose intolerance was found in an additional 3.5% of patients. Overall, 16.4% of patients had previously known diabetes. The decrease in fasting plasma glucose criterion from 7.8 to 7.0 mmol/l resulted in a 2.2% versus a 1.6% prevalence of new diabetes. Several risk factors were reported in a significantly greater proportion of patients with new glucose intolerance and either new and known diabetes compared with the normal glucose tolerance group of patients. CONCLUSIONS Routine screening for diabetes by family physicians is justified in patients > or =40 years of age, given the finding of previously undiagnosed diabetes in 2.2% of these patients and newly diagnosed glucose intolerance in an additional 3.5% of these patients. Another 16.4% of primary care patients > or =40 years of age have known diabetes. This has important implications regarding health resources and physician education.