The increase in the use of electronic patient-reported outcome (ePRO) instruments has presented study teams with considerations not previously encountered with paper. Specifically, in an effort to minimize missing data, there is now the opportunity of requiring subjects to provide a response to an item before allowing the subject to proceed to the next item. While the ability to require subjects to respond to ePRO items would seem to guarantee a complete data set, it raises questions about the conditions under which it is appropriate to require subjects to respond to the items in an instrument. This article provides guidance on the circumstances under which allowing a subject to opt out of responding to ePRO items may be appropriate. Three main scenarios are discussed: (1) requiring subjects to complete all items in all the instruments in the study, (2) allowing subjects to opt out of at least some selective items that do not support key primary or secondary endpoints, and (3) allowing subjects to opt out of responding to any or all items in the study. For either of the 2 scenarios allowing the subject to opt out of responding to an item, the use of programmed edit checks is highly recommended to confirm that the subject intended to 'skip' or 'opt out of' the item. This ensures that, at the end of the study, the database contains an explicit data point indicating when a subject has actively decided to skip an item. While this article is focused on patient-reported outcomes, the issues raised could also apply to other clinical outcome assessments, such as clinician- and observer-reported outcomes.
