BMC Public Health 2007, 7:74 http://www.biomedcentral.com/1471-2458/7/74 Patients from the participating GPs, who are scheduled to visit the DCS for their annual visit, are sent an informa- tion letter on the study. This letter is announced in the tel- ephone call that the reception of the DCS has with the patient to make an appointment for their annual visit at the medical assistant. Patients visit the medical assistant for their annual physi- cal examination of the DCS. The medical assistant checks eligibility of the patient for the study. Patients are eligible if they meet the following inclusion criteria: diagnosis of type 2 diabetes, between 40 and 75 years of age, able to understand the Dutch language in order to understand the study protocol, written informed consent and question- naires, high risk for cardiovascular disease and diabetic complications. Patients are considered at risk if, according to measurements of the previous annual visit, HbA1c ≥ 7.0 % and/or body mass index ≥ 27.0 kg/m2 and/or the patient smokes. In addition, all newly diagnosed patients, who do not have annual check-up results available, are considered eligible, based on the fact that all new patients need to learn how to deal with their diabetes. If all inclu- sion criteria are met, the medical assistant explains the purpose of the study and patients are asked if they are interested in participation. All patients must sign a written informed consent form. Subsequently, physical measurements are performed, which include body weight, waist circumference, blood pressure, and drawing of blood samples (to assess fasting blood glucose, HbA1c, total cholesterol, HDL-cholesterol and triglycerides). In addition, patients are given a self- administrated questionnaire to fill in at home, including questionnaires on physical activity, dietary intake, smok- ing status, determinants of behaviour according to the ASE-model, quality of life, depression, general health and patient satisfaction. The responsible GP is informed that the patient is participating in the study. During the study, GPs receive fax forms from the diabetes nurses and dieti- cians advising on required medication changes for a spe- cific patient. Treatment allocation Patients are randomly assigned to either the intervention group, receiving CBT in addition to the managed diabetes care or the control group, receiving managed diabetes care only. Approximately three weeks after the visit to the med- ical assistant, patients are scheduled for either the first intervention or control session to the diabetes nurse and dietician. Block randomisation is performed within the general practices in order to eliminate the influence of different treatments of general practitioners. From each general practice, half of the patients are randomised to the inter- vention group or the control group. The principle investi- gator (LMCW), who is not involved in the selection and treatment of patients, prepared a randomisation list using series of random numbers [36]. Random permuted blocks of 4 patients are made to ensure equal distribution of patients for each general practice. The manager of the DCS, who is not involved in the patients' care, allocates the patient to one of the two groups by using the randomi- sation list. The flow of the patients is registered by the principal investigator (LMCW), according to a flow dia- gram recommended by the CONSORT statement [37]. Reasons for withdrawal are registered by the medical assistant. Figure 1 shows the design of the study. Blinding Patients, diabetes nurses and dieticians cannot be blinded to the intervention. The medical assistants are blinded as far as possible. They have close contact with the diabetes nurses and dieticians within the DCS and therefore we cannot guarantee the blinding of the medical assistants. However, they are not involved in the intervention. The principal investigator, the GPs and their practices nurses remain blinded during the entire intervention. This is achieved by giving instructions to the patients prefera- bly not to communicate about the intervention with their GPs and practice nurses. To evaluate the success of blind- ing, GPs will be asked to fill in a questionnaire to investi- gate to which group each of their participating patients they believed were allocated. Interventions Control group Patients allocated to the control group receive managed diabetes care provided by the DCS. This managed diabetes care consists of three elements. Firstly, these patients are invited by means of a telephone call from the reception of the DCS to make an appoint- ment for an annual physical examination at the medical assistant. Secondly, the patient visits a diabetes nurse and dietician, for 30 minutes each, in order to receive general information and advice on diabetes problems, dietary intake and physical activity. The results of the physical examination and the recommendations of the diabetes nurses and dietician are sent to the patients' GP, in order to stimulate the GP to follow the guidelines of the Dutch College of General Practitioners [17,18]. Thirdly, the DCS coordinates the care of the patient between the general practices and secondary diabetes care. Patients in the control group are scheduled for one visit to the diabetes nurse and for one visit to the dietician; fol- low-up visits are optional. Page 4 of 10 (page number not for citation purposes)