Cockayne 2017.

Study characteristics
Methods	Parallel RCT, individuals randomised
Data	UK and Ireland, in either primary or secondary care settings. Participants who could be randomised as there was sufficient capacity in the clinics to see them. Total n = 193; mean age 78.1 (6.8) years; 56.5% females.
Comparisons	Intervention group 1 received an optimised version of the participant information sheet and invitation letter developed through bespoke user testing. Intervention group 2 received an optimised template‐developed participant information sheet and the original invitation letter. Control group received the control participant information sheet for the host trial and control invitation letter.
Outcomes	Proportion of participants retained in the trial post‐randomisation
Notes	Retention period: 3 months.
Risk of bias
Item	Authors' judgement	Support for judgement
Allocation concealment?	Yes	Participants were then sent the allocated invitation pack by members of the research team based at the University of York.
Adequate sequence generation?	Yes	An independent data manager, who was not involved in the recruitment of participants, generated the allocation sequence for the embedded methodology trial electronically
Blinding of participants and personnel?	Yes	The researchers, participants and podiatrists were blind to the allocation.
Blinding of outcome assessment?	Yes	The researchers, participants and podiatrists were blind to the allocation.
Incomplete outcome data addressed? All outcomes	Yes	No concerns raised.
Free of selective outcome reporting?	Yes	No concerns raised.
Other sources of bias	Yes	No further concerns raised.
Overall Risk of Bias	Yes	Low