Denig 2014.

Study characteristics
Methods	Randomised controlled trial, 2 × 2 factorial
Participants	Participants with type 2 diabetes mellitus aged < 65 years managed in primary care setting Inclusion criteria: no additional criteria reported Exclusion criteria: people with myocardial infarction (MI) in preceding year, stroke, heart failure, angina, or terminal illness 344 participants randomised at baseline (n = 225 intervention, n = 119 for usual care group) Mean (SD) age: 61.7 (8.5), 44% women, > 90% white, 100% diabetes mellitus; high‐rate of baseline treatment (76% treated with statin)
Interventions	Intervention group: decision aid for people with diabetes mellitus that provided individually‐tailored risk information and treatment options for multiple cardiovascular risk factors; the decision‐aid was offered to participants before a regular diabetes mellitus check‐up and to healthcare provider during the consultation Comparison group: usual care For this systematic review, groups randomised to the decision aid, which provided a CVD risk score, were compared to those in the usual care group (who did not receive a decision aid)
Outcomes	Primary outcome: diabetes empowerment scale Secondary outcome: changes in drug prescription in those with high HbA1c, systolic blood pressure, or LDL; self‐efficacy; satisfaction; negative emotions; and general health status (EQ‐5D); smoking status 306 participants analysed for the study's primary outcome (n = 199 intervention, n = 107 comparison). Not explicitly stated how many were analysed for secondary outcomes obtained from the electronic health record Follow‐up: 6 months before and after intervention
Study funding sources	Funded by Netherlands Organization for Health Research and Development
Notes	4 different formats of the decision aid were tested in exploratory analyses but outcomes for participants allocated to any decision aid were combined by the study authors in this manuscript and was similarly done for this systematic review
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"A stratified computer generated allocation sequence was used."
Allocation concealment (selection bias)	Low risk	"We used a predefined computer algorithm with a blockwise scheme to conceal the allocation process from the healthcare provider."
Blinding of participants and personnel (performance bias) All outcomes	High risk	Participants and personnel not blinded
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	High‐risk for patient‐reported outcomes Low‐risk for clinical outcomes (automatic data extraction from database)
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	31 participants excluded (22 intervention vs 9 control); excluded from analysis
Selective reporting (reporting bias)	Low risk	All outcomes from protocol reported
Other bias	High risk	Randomisation occurred within a practice, increasing the risk for contamination. Decision aid was accessed for 88% (198/225) of intervention participants but only 46% (103/225) of intervention participants received all basic elements of the intervention