Protocol component	ARM of interest	Reference arm	Adjusted Odds Ratio (95% CI)
Email (x4) addition	ARM 5: Email (x4) + mail + telephone	ARM 1: Mail + telephone	1.12 ( 0.99 , 1.27 )
QR code added to paper invitation	ARM 2: Paper invitation + email (x2) + mail (x2)	ARM 9: Paper invitation (URL only) + email (x2) + mail (x2)	1.02 ( 0.87 , 1.19 )
Second mailing instead of 3rd email reminder	ARM 2: Paper invitation + email (x2) + mail (x2)	ARM 3: Paper invitation + email (x3) + mail	1.25 ( 1.06 , 1.47 ) **
Paper invitation instead of 2 additional email reminders	ARM 2: Paper invitation + email (x2) + mail (x2)	ARM 6: Email (x4) + mail (x2)	1.01 ( 0.86 , 1.18 )
Two texts instead of two email reminders	ARM 7: Text + email + text + email + mail (x2)	ARM 6: Email (x4) + mail (x2)	1.25 ( 1.08 , 1.45 ) **
Text invitation and second mailed survey instead of paper invitation	ARM 7: Text + email + text + email + mail (x2)	ARM 8: Paper invitation + text + email (x2) + mail	1.34 ( 1.16 , 1.56 ) ***
Mailed survey	ARM 5: Email (x4) + mail + telephone	ARM 4: Email (x4) + telephone	1.30 ( 1.15 , 1.46 ) ***
Telephone addition (instead of 2nd mailing)	ARM 5: Email (x4) + mail + telephone	ARM 6: Email (x4) + mail (x2)	2.41 ( 2.10, 2.76 ) ***
Text instead of email for 1 reminder	ARM 8: Paper invitation + text + email (x2) + mail	ARM 3: Paper invitation + email (x3) + mail	1.15 ( 0.98 , 1.36 )