The Between-Visit Gap Is Where Participants Quietly Drop Out

Most dropouts don't happen at a dramatic moment. They happen quietly, between visits, when a participant stops feeling like anyone at the site is paying attention. By the time someone stops answering the phone, the decision was usually made weeks earlier.

Communication won't fix a brutal protocol. But in most site datasets, a meaningful share of withdrawals trace back to confusion, inconvenience, or feeling unimportant — all of which are communication problems you control.

Set expectations before the first dose

The single highest-leverage retention conversation happens at consent. Not the consent form itself — the plain-language version you give afterward.

Walk through, out loud:

• Total number of visits and roughly how long each one runs
• Which visits are long or unpleasant (fasting, PK draws, biopsies) and why
• What the participant has to do at home, every day, with no help from you
• When they'll hear from you between visits, and from whom
• What happens if they miss a visit (answer: we reschedule, you're not in trouble)

Participants who are surprised later feel misled, even when nothing was hidden. Surprise is the enemy.

Name a person, not a site

"Call the office" produces far fewer calls than "call Marcus." Give every participant one named primary contact with a direct number, plus a named backup. Put it on a card that fits in a wallet, not a folder that goes in a drawer.

Then have that named person make the between-visit contact. A voicemail from a stranger reads like a collections call. A text from the coordinator who drew their blood last month reads like a check-in.

Build a between-visit cadence and write it down

Ad hoc contact is the default at busy sites, which means the quiet, compliant participants get ignored while problem cases absorb all the attention. Define a minimum cadence per study and track it like any other protocol requirement:

1. 48 hours after randomization. How's the dosing going? Any questions about the diary?
2. Midway between every visit pair. Short text: confirm adherence, flag issues, no ask.
3. One week before each visit. Confirm date, time, parking, fasting, what to bring.
4. 48 hours before. Short reminder with the named contact's number.
5. After any missed or rescheduled visit. Same day, warm tone, no scolding.

For long studies, add something that isn't a request: a brief note at the halfway mark thanking them and telling them how many visits remain. Participants consistently say progress markers help.

Match the channel to the person

Ask at enrollment how they prefer to be reached and honor it. Older participants often prefer calls; working-age participants often ignore them entirely. Text is excellent for reminders and terrible for anything requiring nuance. Clinical concerns always get a voice conversation.

Ask the question that predicts dropout

Add one item to every visit: "Is anything about this study getting harder to manage?" Transportation, childcare, work schedules, and diary fatigue surface in response to that question weeks before they surface as a withdrawal. Most of those problems have solutions — a different appointment slot, ride reimbursement explained properly, a diary refresher — if you hear about them in time.

Close the loop on study results

Participants who feel used don't return for your next study. Tell them when results are expected, and actually follow up when they publish. Retention for study two starts with how you ended study one.