van Roosmalen 2004.

Methods	Study design: cluster‐randomized trial Unit of allocation: family Unit of analysis: patient Power calculation: done
Participants	Care setting: specialized care; setting: unclear; the Netherlands Health professionals: number unknown; type: unclear; level of training: unknown Patients: 88, deleterious BRCA1/2 mutation; female
Interventions	Multifaceted intervention: patient‐mediated intervention (SDMI+DA) Quote: "The SDMI was provided by a trained research assistant and consisted of three sessions with an interval of 1 to 2 weeks. In the first session, individual values for the treatment options (screening and prophylactic surgery) were assessed in a face‐to‐face interview by use of the TTO method.In the second session, the TTO interview was repeated by telephone...In the first part of the study (T1 to T3; Fig 1), not reported here, women were randomly assigned to the DA group (the DA was provided 2 weeks after blood sampling) or to the control group (receiving usual care)." see figure 1 pages 3294‐3295 Single intervention (control): patient‐mediated intervention (DA) Quote: "The DA was added to usual care and was to be viewed at home. It consisted of a brochure and video providing information on screening and prophylactic surgery, and the physical, emotional, and social consequences." page 3295
Outcomes	Perceived participation in decision making (continuous)
Notes	Additional information Number of approached patients (eligible): 453 Number of patients per physician: not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Comment: computer generated.
Allocation concealment (selection bias)	Unclear risk	Comment: not specified.
Blinding (performance bias and detection bias) Participant‐reported outcome	High risk	Quote: "Neither study participants nor members of the study staff were blinded to intervention assignment." page 3296
Incomplete outcome data (attrition bias) Participant‐reported outcome	Low risk	Comment: the follow‐up at T4 was 100%. At T5, one woman from the control group was lost to follow‐up.
Selective reporting (reporting bias)	Unclear risk	Comment: study protocol not available.
Other bias	Low risk	Comment: no evidence of other risk of biases.
Baseline measurement? Participant‐reported outcome	Unclear risk	Comment: no baseline measure of our primary outcome.
Protection against contamination?	Low risk	Quote: "Randomization took place by family to avoid contamination." page 3296
Baseline characteristics patients	Low risk	Comment: reported and similar (See table 1).
Baseline characteristics healthcare professionals	Unclear risk	Comment: no report of characteristics.