Table 4 Participant engagement activities

1. Referral to study team by health authorities

 – Collaborate with referral partners to obtain participant contact information, preferred modes and times of contact, consent for initial contact

 – Assign each participant to one field interviewer throughout the study, where possible

 – Contact participant using study cell phone with text and email functions

 – Use different modes and times of contact and obtain three alternative contacts

 – Answer questions and offer flexibility in timing and location of interview

 – Provide 24-h reminders using preferred communication mode (e.g., text messages)

 – Enquire at each encounter if there is a change in contact information

 – Accommodate interview rescheduling

3. Baseline interview (in-person)

 – Establish rapport using effective communication techniques

 – Adopt a professional (neutral, non-judgmental) manner

 – Apply risk-mitigation training (interviewer safety)

 – Provide essential study materials outlining the research process and interview dates

 – Explain study purpose and confidentiality, answering questions and providing time to consider

 – Use visual aids to convey the type, length and timing of research interviews

 – Verify eligibility and obtain written informed consent

 – Verify contact information and alternative contacts

 – Use audio aids for survey items sensitive to reporting bias

 – Provide meaningful honoraria such as gift cards for local department stores

 – Collect information to facilitate rapport at follow-up interviews, such as preferred name