Table 3 Examples of trial-specific group-text messages in English

• Welcome SMS-text message

Welcome to StAR* thank you for participating. The trial cell is 0XXXXXX120 (save on phone). We will never ask for personal or banking details. Dr[NAME](StAR*@VAN)

• Trial specific SMS-texts

Pls remember your participation in StAR* is voluntary. Call, text, or send plz cal 0XXXXXX372 (its free) if you need to withdraw. Thnx Dr [NAME] (StAR*@VAN)

Pls remember participating in StAR is free. We do not charge you for the SMS-texts we send to you. Thnx Dr [NAME] (StAR@VAN)

• Birthday SMS-text

Hi [NAME]. Happy birthday, have a great day. Thnx [NAMES](Health Team & StAR*@VAN)