Alvaro 2011b.

Study characteristics
Methods	Study design: cluster‐RCT Study duration: 8 weekends, beginning in Spring 2009 Study follow‐up period: not reported
Participants	Country: USA (Arizona) Setting: Flea market Number: intervention group (87); control group (69) Mean age ± SD (years): not reported Sex: not reported
Interventions	An organ donation information booth featuring Arizona Organ Donor Registry brochures and registration forms, along with two field workers associated with the Donor Network of Arizona, were present for eight weekends consecutively at the flea market. The workers were made available to answer any questions related to the registration process in Arizona, explaining the nature of the process, and offering visitors the opportunity to complete a registration form on the spot. Intervention versus control weekends order was determined using a coin flip method Intervention group (immediacy) During intervention weekends banners featuring either the phrase “Register Here!” or “Register Now!”were displayed to visitors Control group (non‐immediacy) During control weekends banners featuring the phrase “Done Vida!” were displayed to visitors
Outcomes	Primary outcome Completed paper registry forms on‐site by the flea market attendees (participants) Intervention group: 67/87 (86%) participants registered Control group: 37/69 (54%) participants registered No adverse events were reported
Notes	Study author contact: Eusebio.Alvaro@cgu.edu
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Authors used coin flip to determine randomisation
Allocation concealment (selection bias)	Unclear risk	Insufficient detail about allocation method
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Insufficient detail about blinding of participants and personnel
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Registration in a donor registry is unlikely to be affected by detection bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Minimal loss to follow up
Selective reporting (reporting bias)	Low risk	Outcome measures reported
Other bias	High risk	Each site could recruit their own participants