Table 1

Characteristics of the included cluster randomised controlled trials

StudyComparisonEffect on end points*Notes
Cleveringa et al. (2008)33Intervention: Patient consultation by a practice nurse+use of a computerised decision support system+guideline-based care+physician support by practice nurse+interdisciplinary care by a specialist team+individualised treatment advice+patient education+physician feedback+recall system+regular patient consultations by practice nurse+physician feedback
versus
Usual diabetes care (not further specified)
Biochemical outcomes
HbA1c (0)
Total cholesterol (+, i)
HDL-cholesterol (0)
LDL-cholesterol (+, i)
Systolic blood pressure (+, i)
Diastolic blood pressure (+, i)
10-year CHD risk (+, i)
Diabetes complications and processes of care
HbA1c below target value† (+, i)
Total cholesterol below target value† (+, i)
LDL-cholesterol below target value† (+, i)
Systolic blood pressure below target value† (+, i)
All treatment targets reached† (+, i)
At baseline, patients in the intervention group had higher HDL-cholesterol levels, were more often smoker and more often had a history of CHD.
Statistical analyses were conducted by intention-to-treat and for missing follow-up data the last observation was carried forward.
Comparisons between the intervention and control group were adjusted for cluster structure.
Sönnichsen et al. (2008)45Intervention: Physician education+guideline-based care+patient education+use of a clinical information system tool+interdisciplinary care by a specialist team+patient reminders+physician reminders+goal setting+shared decision-making patient and physician+regular consultations
versus
Usual diabetes care (not further specified)
Biochemical outcomes
HbA1c (0)
Total cholesterol (+, i)
HDL-cholesterol (0)
LDL-cholesterol (0)
Systolic blood pressure (0)
Diastolic blood pressure (0)
Body mass index (+, i)
Triglycerides (0)
Creatinine (0)
Diabetes complications and processes of care
To the guidelines adherent:
– number of eye examinations† (+, i)
– number of foot examinations† (+, i)
– provision of patient education† (+, i)
– regular HbA1c checks† (+, i)
At baseline, patients in the intervention group had a higher BMI and higher cholesterol levels than patients in the control group.
Statistical analyses were conducted by intention-to-treat and for missing follow-up data the last observation was carried forward.
Comparisons between the intervention and control groups were adjusted for cluster structure and baseline characteristics.
Frei et al. (2010)44Intervention: Specialist team involving a practice nurse+practice nurse education+physician education+physician support by practice nurse+regular independent patient consultations by practice nurse+use of a clinical information system tool+guideline-based care+physician feedback+patient information leaflets+self-management support for patient+patient treatment groups
versus
Usual diabetes care (not further specified)
Biochemical outcomes
HbA1c (0)
Total cholesterol (0)
HDL-cholesterol (0)
LDL-cholesterol (+, i)
Systolic blood pressure (+, i)
Diastolic blood pressure (+, i)
Body mass index (0)
Fasting blood glucose (0)
Patient-reported outcomes
Diabetes complications and processes of care
Number GP visits† (0)
Change in antidiabetic therapy (0)
Change in antihypertensive therapy (0)
Change in lipid-lowering therapy (0)
There were no baseline differences in patient characteristics between intervention and control group.
Statistical analyses were conducted by intention-to-treat and for missing follow-up data the last observation was carried forward.
Comparisons between intervention and control group were adjusted for cluster structure and baseline characteristics.
Webb et al. (2010)43Intervention: Structured patient education+lifestyle advice and self-management with ongoing (bimonthly) professional support+individualised management+guideline-based care+shared decision-making patient and healthcare professional+annual screening for diabetic complications+care delivered by a specialist team (specialty doctor, diabetes nurse educator, and a dietician)+patient reminders+physician reminders
versus
Usual diabetes care (not further specified)
Biochemical outcomes
HbA1c (+, i)
Total cholesterol (+, i)
LDL-cholesterol (+, i)
HDL-cholesterol (0)
Systolic blood pressure (+, i)
Diastolic blood pressure (+, i)
Body mass index (+, i)
Weight (+, i)
Waist circumference (0)
Triglycerides (0)
5-year CHD risk (+, i)
5-year CVD risk (+, i)
Patient-reported outcomes
Health-related quality of life (0)
Diabetes complications and processes of care
Hypoglycaemia† (+, i)
Use of antihypertensive drugs† (+, i)
Use of lipid-lowering drugs† (+, i)
Use of antiplatelet therapy† (+, i)
Use of metformin† (0)
Use of sulfonylurea† (0)
At baseline, more patients in the intervention group were taking antihypertensive medication when entering the study and had higher total and LDL-cholesterol levels.
Statistical analyses were conducted by intention-to-treat. It was not reported whether or not data were missing and how missing data were handled.
Comparisons between intervention and control group were adjusted for cluster structure and baseline characteristics (except quality of life which had not been measured at baseline).
Janssen et al. (2009)39Intervention: Physician education+diabetes nurse education+lifestyle advice+guideline based care+physician support by diabetes nurse+evaluation and feed-back sessions diabetes nurse+frequent patient consultations with diabetes nurse+shared decision-making patient, physician and diabetes nurse+physician reminders+patient reminders
versus
Usual diabetes care (not further specified)
Biochemical outcomesHbA1c (+, i)
Total cholesterol (+, i)
LDL-cholesterol (+, i)
HDL-cholesterol (0)
Systolic blood pressure (+, i)
Diastolic blood pressure (+, i)
Body mass index (+, i)
Fasting blood glucose (+, i)
Triglycerides (0)
Patient-reported outcomes
Health-related quality of life (0)
Diabetes complications and processes of care
Hypoglycaemia† (0)
There were no baseline differences in patient characteristics between the intervention and control group.
Statistical analyses were conducted by intention-to-treat and for missing follow-up data the last observation was carried forward.
Comparisons between the intervention and control group were adjusted for baseline characteristics, and clustering at practice level.
Griffin et al. (2011)46This study combined the data after five years of a multifaceted care intervention from the (1) Addition-Denmark study (Lauritzen et al40), (2) the Addition-Netherlands study (Janssen et al39), (3) the Addition-Cambridge study (Echouffo et al35) and (4) the Addition-Leicester study (Webb et al43) in a meta-analysis.Biochemical outcomes
HbA1c (+, i)
Total cholesterol (+, i)
LDL-cholesterol (+, i)
HDL-cholesterol (0)
Systolic blood pressure (+, i)
Diastolic blood pressure (+, i)
Body mass index (0)
Weight (0)
Waist circumference (0)
Triglycerides (0)
Creatinine (+, c)
Patient-reported outcomes
Health-related quality of life (0)
Diabetes complications and processes of care
All-cause mortality (0)
CVD mortality (0)
Myocardial infarction (0)
Stroke (0)
Revascularisation procedures (0)
Hypoglycaemia† (0)
Meeting target values for:
 HbA1c (+, i)
 Blood pressure (+, i)
 Total cholesterol (+, i)
Use of any glucose-lowering drugs (+, i)
Change in any antihypertensive drugs (+, i)
Change in any cholesterol-lowering drugs (+, i)
Baseline characteristics were well matched between intervention and control group. In Denmark however, more patients were identified in practices assigned to the intervention arm then in those assigned to control arm. And in the intervention group, more patients had a history of ischaemic heart disease.
Statistical analyses were conducted by intention-to-treat and patients with missing outcome values at baseline were excluded from the analyses. Those with missing outcome baseline values were included according to the missing indicator method.
Comparisons between intervention and control group were adjusted for cluster structure and baseline characteristics.
Olivarius et al. (2001)41Intervention: Patient follow-up every three months+annual screening for diabetes complications+shared decision-making patient and physician+physician feedback+goal setting+clinical guidelines+physician education+patient leaflets and folders+lifestyle advise+protocol based care+physician recall system
versus
Usual diabetes care (not further specified)
Biochemical outcomes
HbA1c (+, i)
Total cholesterol (+, i)
Systolic blood pressure (+, i)
Diastolic blood pressure (0)
Weight (0)
Fasting blood glucose (+, i)
Triglycerides (0)
Creatinine (0)
Diabetes complications and processes of care
Overall mortality† (0)
Severe hypoglycaemia† (0)
Diabetic retinopathy† (0)
Non-fatal myocardial infarction† (0)
Non-fatal stroke† (0)
Peripheral neuropathy† (0)
Microalbuminuria† (0)
Angina pectoris† (0)
Intermittent claudication† (0)
Number of consultations† (+, i)
Number of referrals to diabetes
clinic† (−, i)
Number of hospital admissions† (0)
Use of metformin† (+, i)
Use of other glucose-lowering drugs† (0)
Use of antihypertensive drugs† (0)
Use of lipid-lowering drugs† (0)
At baseline, more patients in the intervention group were excluded because of severe somatic disease than in the control group. Furthermore, occupation and smoking habits differed between the two groups.
Statistical analyses were conducted by intention-to-treat. It was not reported whether or not data were missing or how missing data were handled.
Comparisons between intervention and control group were adjusted for cluster structure and baseline characteristics.
  • *+=positive effect; 0=no effect; −=negative effect; i=favouring intervention group; u=favouring control (usual care) group. The effects of the intervention are represented by the difference in change from baseline to follow-up between the intervention and control group.

  • † The effect of the intervention is represented by a difference in proportions of patients at follow-up between the intervention and control group.

  • CHD, coronary heart disease; CVD, cardiovascular (heart) disease; GP, general practitioner; T2DM, type 2 diabetes mellitus.