Table 2.
Key notification and reminder messages delivered by the Food Label Trial app
| Message description | Trigger | Time point and frequency | Type |
| Notification informing of ineligibility for the trial; offered a link to the FoodSwitch app. | First eligibility check failed | Once after the screening questionnaire | In-app message |
| Reminder to complete the registration or baseline questionnaire | Registration form not completed | Two days after consent, then once a week up to 4 times, then once a month until 5 weeks before the overall trial recruitment completion | Push notification |
| Reminder to record at least 15 items during week 1 | User submitted a list of purchased products during week 1, and the total number of items recorded by the user to date is less than 15 | After every submitted list that meets the criteria | In-app message |
| Notification that the product list has been successfully sent | User submitted a list of purchased products, and it was successfully transmitted to the trial database. The number of products recorded during week 1 is 15 items or more | After every submitted list that meets the criteria | In-app message |
| Reminder to record food purchases (baseline phase) | User has not sent any product lists since the beginning of week 1 | At days 3 and 5 of week 1 | Push notification |
| Reminder to keep recording food purchases (intervention phase) | User has not been sending through any new product lists | At days 4, 6, 9, 12, 18, and 24 since the last product list was sent OR since the beginning of the intervention phase | Push notification |
| Reminder that the trial is ending soon | Day 26 of the intervention phase | Day 26 of the intervention phase | Push notification |
| Request to complete the follow-up questionnaire | Day 28 of the intervention phase | Day 28 of the intervention phase | In-app message |
| Reminder to complete the follow-up questionnaire | User has not completed the follow-up questionnaire | Days 6, 12, 18, 24, and 30 from completion of the intervention phase | Push notification |
| Notification of the trial completion | User completed the follow-up questionnaire | Once after the follow-up questionnaire | In-app message |