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Item 18b: Plans to promote participant retention and complete follow-up, including list of any outcome data to be collected for participants who discontinue or deviate from intervention protocols.

Example 1

“5.2.2 Retention

. . . As with recruitment, retention addresses all levels of participant.

At the parent and student level, study investigators and staff:

    • Provide written feedback to all parents of participating students about the results of the “health screenings” . . .
    • Maintain interest in the study through materials and mailings . . .
    • Send letters to parents and students prior to the final data collection, reminding them of the upcoming data collection and the incentives the students will receive.

At the school level, study investigators and staff:

    • Provide periodic communications via newsletters and presentations to inform the school officials/staff, students, and parents about type 2 diabetes, the current status of the study, and plans for the next phase, as well as to acknowledge their support . . .
    • Become a presence in the intervention schools to monitor and maintain consistency in implementation . . . be as flexible as possible with study schedule and proactive in resolving conflicts with schools.
    • Provide school administration and faculty with the schedule or grid showing how the intervention fits into the school calendar . . .
    • Solicit support from parents, school officials/staff, and teachers . . .
    • Provide periodic incentives for school staff and teachers.
    • Provide monetary incentives for the schools that increase with each year of the study . . .
Table 1. Study Provided Compensation
Intervention School * school program enhancement
* PE [physical education] class equipment required to implement intervention
* food service department to defray costs of nutrition intervention
* $2000 in year 1, $3000 in year 2, $4000 in year 3
* ~$15,000 over 3 years

* $3000/year
Control School * school program enhancement * $2000 in year 1, $4000 in year 2, $6000 in year 3

. . .

All * return consent form (signed or not)
* participation in health screening data collection measures and forms
* gift item worth ~ $5

* $50 baseline (6th grade), $10 interim (7th grade), $60 end of study (8th grade)
Intervention Parents * focus groups to provide input about family outreach events and activities * $35/year per parent, up to 2 focus groups per field center, 6-10 participants per focus group
 286 [Adapted from original table]

Example 2

“5.4 Infant Evaluations in the Case of Treatment Discontinuation or Study Withdrawal

All randomized infants completing the 18-month evaluation schedule will have fulfilled the infant clinical and laboratory evaluation requirements for the study . . .

All randomized infants who are prematurely discontinued from study drug will be considered off study drug/on study and will follow the same schedule of events as those infants who continue study treatment except adherence assessment. All of these infants will be followed through 18 months as scheduled.

Randomized infants prematurely discontinued from the study before the 6-month evaluation will have the following clinical and laboratory evaluations performed, if possible: . . .

    • Roche Amplicor HIV-1 DNA PCR [polymerase chain reaction] and cell pellet storage
    • Plasma for storage (for NVP [nevirapine] resistance, HIV-1 RNA PCR and NVP concentration)
    • . . .

Randomized infants prematurely discontinued from the study at any time after the 6-month evaluation will have the following clinical and laboratory evaluations performed, if possible:
. . .
5.5 Participant Retention

Once an infant is enrolled or randomized, the study site will make every reasonable effort to follow the infant for the entire study period . . . It is projected that the rate of loss-to-follow-up on an annual basis will be at most 5% . . . Study site staff are responsible for developing and implementing local standard operating procedures to achieve this level of follow-up.

5.6 Participant Withdrawal

Participants may withdraw from the study for any reason at any time. The investigator also may withdraw participants from the study in order to protect their safety and/or if they are unwilling or unable to comply with required study procedures after consultation with the Protocol Chair, National Institutes of Health (NIH) Medical Officers, Statistical and Data Management Center (SDMC) Protocol Statistician, and Coordinating and Operations Center (CORE) Protocol Specialist.

Participants also may be withdrawn if the study sponsor or government or regulatory authorities terminate the study prior to its planned end date.

Note: Early discontinuation of study product for any reason is not a reason for withdrawal from the study.”287


Trial investigators must often seek a balance between achieving a sufficiently long follow-up for clinically relevant outcome measurement,122;288 and a sufficiently short follow-up to decrease attrition and maximise completeness of data collection. Non-retention refers to instances where participants are prematurely ‘off-study’ (i.e., consent withdrawn or lost to follow-up) and thus outcome data cannot be obtained from them. The majority of trials will have some degree of non-retention, and the number of these ‘off-study’ participants usually increases with the length of follow-up.116

It is desirable to plan ahead for how retention will be promoted in order to prevent missing data and avoid the associated complexities in both the study analysis (Item 20c) and interpretation. Certain methods can improve participant retention,67;152;289-292 such as financial reimbursement; systematic methods and reminders for contacting patients, scheduling appointments, and monitoring retention; and limiting participant burden related to follow-up visits and procedures (Item 13). A participant who withdraws consent for follow-up assessment of one outcome may be willing to continue with assessments for other outcomes, if given the option.

Non-retention should be distinguished from non-adherence.293 Non-adherence refers to deviation from intervention protocols (Item 11c) or from the follow-up schedule of assessments (Item 13), but does not mean that the participant is ‘off-study’ and no longer in the trial. Because missing data can be a major threat to trial validity and statistical power, non-adherence should not be an automatic reason for ceasing to collect data from the trial participant prior to study completion. In particular for randomised trials, it is widely recommended that all participants be included in an intention-to-treat analysis, regardless of adherence (Item 20c).

Protocols should describe any retention strategies and define which outcome data will be recorded from protocol non-adherers.152 Protocols should also detail any plans to record the reasons for non-adherence (e.g., discontinuation of intervention due to harms versus lack of efficacy) and non-retention (i.e., consent withdrawn; lost to follow-up), as this information can influence the handling of missing data and interpretation of results.152;294;295

18a: Data collection methods 19: Data management
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