Dropouts missing data

What are the implications of the trial procedures on the potential dropout rate and the extent of missing data ... 

What impact are the dropouts and missing data likely to have on the definition of analysis sets and in particular our ability to align with the principle of intention to treat ... 

It is worth noting here that documentation of premature withdrawals from a study is important for various reasons. The implications of premature withdrawals are different in the analysis of safety and the analysis of efficacy. From a safety perspective, these data relate to tolerability of the drug. From an efficacy perspective, dropouts lead to missing data, and the way(s) that missing data are addressed is important from the point of view of full interpretation of the analysis presented. The issue of missing data is addressed in Section 11.2.4. 

Important features of the analysis, including adjustments for interim analyses, handling of dropouts, and missing data, should be included. Information on the selection and adjustments for covariate or prognostic factors such as baseline measurements, demographics, and concomitant therapy, together with the results of analyses, should be included. 

The importance of the execution model cannot be overemphasized. The execution model describes how the study is carried out and deviations from the protocol. There are deviations from the protocol that are done by the patient such as refusal to enter the study, dropouts, and patient noncompliance. Other deviations are due to practitioner behavior such as missing data, wrong recording of data, or improper preparation of doses. It must be decided whether the deviations are completely at random or if there is some influencing factor that may result in protocol deviations. For example, would patients experiencing adverse events have a greater tendency to drop out of the study ... 

By doing this, the statistician becomes familiar with the strongest data trend and will be able to assess the frequency with which data with a certain variable are missing. This includes rate, timing, reasons for dropout, and some of the other easily noted results. 

All research personnel must search for clues about safety events from many sources, such as information in clinical records at the study sites information in data collection forms (e.g. CRFs, diary cards, quality-of-life forms, psychiatric rating scales, etc.), occurrence of missed and/or unscheduled visits, dropouts and withdrawals use of any concomitant medications/devices and abnormal laboratory data. AEs may also occur simply as a result of study procedures and study participation. Information about definitions of AEs and requirements for reporting AEs must be clearly stated in the protocol and explained to the site staff, who must also be educated in the correct procedure and immediate requirement for reporting any AE suspected to be serious or unexpected as per the regulatory definitions. 

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