Key item requirements

A key item must:

• Be in a repeating section, if the key is for an itemset.
• Be in a repeating form or in a non-repeating section of the repeating form, if the key is for a repeating form.

A key item must not:

• Be a hidden item.
• Be a compound item.
• Be formatted as a checkbox.
• Have a caption that is aligned at the top or bottom of the control.
• Be in a nested control structure, unless it is at the top of the hierarchy and conforms to other eligibility requirements.

  For example, consider an item called Continuing in an Adverse Events form. The Continuing item has a YesNo codelist formatted as radio buttons, and the No codelist item has a conditional date time item called End Date. In this example, the Continuing item can be a key item, but the End Date item cannot.