If you don’t, you need to. Handling one incorrectly could get you or your organization in serious hot water.
Modifier extensions are different to — and less common — than regular extensions.
A modifier extension changes the meaning of the resource or element that contains it.
Example: A contact listed for a Patient has a modifier extension called “do-not-contact.”
Ignoring this and using the contact information in any way could be a costly or even dangerous mistake.
If your app encounters a resource or element with a modifier extension and doesn’t understand how it should be used, you should reject that resource or element.
More: https://hl7.org/fhir/extensibility.html#modifierExtension
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