Screening for type 2 diabetes in general practice

Abstract

The presented studies were conducted within the framework of the international ADDITION study (Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen-Detected Diabetes in Primary Care), a randomised controlled trial in 3,057 screen-detected type 2 diabetic patients. The aim of ADDITION is to evaluate whether screening for type 2 diabetes in general practice is feasible and subsequent intensified, multifactorial treatment beneficial. Intensified treatment consisted of pharmacological treatment combined with lifestyle education. From 2002 to 2004, 56,978 subjects, aged 50-70 years, from 79 general practices in the Netherlands, were invited to participate in a screening programme starting with a questionnaire. Eventually, 586 (1.0%) diabetic patients were diagnosed. Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) were assessed in 1,011 participants (1.8%). The risk score was higher if glucose metabolism was more disturbed. The yield of population-based screening is low. Case-finding in general practice might be more appropriate to detect undiagnosed diabetes. The yield of screening varied widely between practices. Outcome measure was the ratio screen-detected diabetic patients/known diabetic patients per practice. The ratio ranged from 0.8% to 20.0% (mean 7.5% 4.5). A lower yield, plausibly reflecting a lower prevalence of undiagnosed diabetes, was not associated with specific GP and practice characteristics. This finding stresses the importance of a screening programme in each practice. Screened persons with IFG had lower weight and blood pressure than those with IGT and diabetes suggesting IFG to be a condition with less risk to develop cardiovascular diseases. When glycaemic control was poorer, levels of BMI, blood pressure and lipids were worse. The increased cardiovascular risk of hyperglycaemia is notably present in overweight persons. People with lower fasting glucose levels at diagnosis may be at an earlier stage of the disease. 498 patients were divided into tertiles of fasting glucose. Cardiovascular risk markers did not differ substantially between tertiles. Coffee consumption (>2 cups daily) was associated with better, alcohol abstinence with worse fasting glycaemic control. SES was not associated with the level of glycaemic control. Analyses with interaction terms between lifestyle and SES appeared to be not significant. Lifestyle behaviours and socioeconomic factors are not helpful to identify specific categories of patients to be screened for diabetes. 1-year results showed improvements of BMI, blood pressure, HbA1c, and cholesterol in the intensively treated group to be significantly better than in the routine care group. At end of follow-up, in the two treatment groups similar health-related quality of life (HRQoL) was reported. Intensified multifactorial treatment of screen-detected diabetic patients in general practice reduces cardiovascular risk factor levels significantly without worsening HRQoL. After three years of follow-up, screened subjects with an elevated risk score but without diabetes had cardiovascular event rates comparable with diabetic patients. During follow-up numbers of prescriptions of cardiovascular medication, practice visits and glucose, lipid, and blood pressure measurements were highest in diabetic patients. Screened non-diabetic subjects are at risk of lacking optimal medical care in order to control for cardiovascular risk factors. They should not be reassured only because of not having diabetes