Treweek 2020a.

Study characteristics
Methods	Parallel RCT, clusters randomised
Data	UK, secondary care setting. All host trial participants were considered in this trial. Total n = 560; age NR; 100% females
Comparisons	Intervention group received a pre‐notification card sent around 1 month before the face‐to‐face primary outcome measurement visit. Control group received no pre‐notification card.
Outcomes	Proportion attending the primary outcome measurement visit.
Notes	Retention period:12 months
Risk of bias
Item	Authors' judgement	Support for judgement
Allocation concealment?	Yes	The list was then passed to the data manager at Tayside Clinical Trials Unit to implement.
Adequate sequence generation?	Yes	Two‐arm, parallel randomised with a 1:1 allocation ratio, stratified by centre. One of the authors prepared a central randomisation list using.
Blinding of participants and personnel?	Yes	All trial team members were blind to host trial allocation. Primary outcome visits were organised, done and recorded by research nurses, who had no knowledge of the SWAT or host trial allocation. However, unclear about participants. However, unblinding not likely to impact objective outcome
Blinding of outcome assessment?	Yes	All trial team members were blind to host trial allocation. Primary outcome visits were organised, done and recorded by research nurses, who had no knowledge of the SWAT or host trial 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