Why is a non-fixed interval not available for selection on the Subject Overview page

Non-fixed intervals can be added for subjects in either of the following:

1. Sidebar
2. Encounters tab of the Subject Overview Details view by clicking the + and selecting the encounter name from the dropdown  

If the project has Screening as an enabled feature, then the option selected for the Interval Type field will determine when the interval is available for subjects.

• Follow-up:  The interval will only be available when the subject has passed screening and is enrolled in the project 
• Screening:  The interval is only available when a subject is in the screening phase of the project

There are times when a non-fixed interval only applies during the screening phase or only during the follow-up phase.  For example, a project may have an non-fixed interval to capture complications from study medication.  That non-fixed interval would not be applicable during the screening phase as the subject would not have started taking the study medication.  Or a subject may need to be washed-off a medication before starting the study, in that situation a non-fixed interval for complications from washing-off medications would only be required during the screening phase.