The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
The Prevention and Treatment of Missing Data in Clinical Trials
ACTIONS FOR DESIGN AND MANAGEMENT TEAMS
This section discusses some techniques that trial design and management teams can use to reduce the frequency of dropouts. First, designers and managers can limit participants’ burden and inconvenience in the data collection stage. This can be done in at least five ways: (1) minimizing the number of visits and assessments, (2) collecting only the information that is needed at each visit, (3) using user-friendly case report forms, (4) using direct data capture that does not require a clinic visit whenever feasible, and (5) allowing a relatively large time window for each follow-up assessment. Examples of information not needed at each visit include aspects of the participant’s medical history and contact information that were provided at earlier visits and information available from medical records. The overall aim is to balance the competing goals of reducing response burden and collecting sufficient information to fully support the analytic goals and to guide the next steps in treatment. (Regarding use of direct data capture to minimize the response burden, it would also be useful to attempt to collect whatever information is available from administrative records.)
Second, design and management teams can increase the incentives for participation and completion by the provision of effective treatments to participants after the trial. Such incentives might include continued access to effective study treatments on extension protocols until the treatment is licensed.
Third, designer and managers can select investigators with a good track record of both enrolling and following participants and collecting complete data in previous trials, and provide good training. The training (and onstudy reinforcement) needs to emphasize the importance of complete data collection and the difference between discontinuing the study treatment and discontinuing data collection. Training should stress the value of collecting data after a participant discontinues the study (or the control) treatment.
As discussed in Chapter 2, many trial sponsors and investigators mistakenly assume that there is little reason for additional data collection when participants discontinue study treatment. But as we emphasize, the continued collection of data is important in many trials. The trial objectives and estimands need to be considered.
Training can also emphasize the importance of the informed consent process as a mechanism for ensuring that participants understand the commitment they are making, including their intent to complete the trial regardless of the treatment they are receiving. Training of investigators and research staff should also emphasize how to work with participants to minimize the extent of missing data (see later in this chapter). Finally, trainers need to know and explain to participants that any decision to withdraw consent is a participant’s decision, not the investigator’s decision. However,