| 1. Follow-up interviews (in-person or telephone) |
| – Emphasize the value of participant’s contribution at each interview and review the study purpose |
| – Provide breaks during lengthier interviews |
| 2. Participant tracking and interview scheduling |
| – Maintain the same field interviewer |
| – Text reminders 1 week and 24 h prior to each interview |
| – Attempt different modes/times/types of contact and alternative contacts (partner/friends/family) |
| – Reminder of ongoing study eligibility even if previous interviews are missed |
| – Offer flexibility in interview location and time and accommodate requests for rescheduling |
| – Encourage participants to update team with changes in personal information |
| 3. Specific tracking protocols |
| – Identify new approaches, vary contact type and frequency, send re-engagement letter |
| 4. Study team support |
| – Review progress reports (completed or missed interviews, requests to withdraw) |
| – Frequent field interviewer meetings and retention training |
