Central labs (Labcorp, Quest, Sonora Quest and BioReference) allow you to pass in clinical notes. These are reflected in the Requisition form that is generated.
Junction also allows you to set these notes, on an order by order basis, or as a Lab Account default.
The Lab Account default is an internal configuration, contact your CSM to set this up.
Order Level Notes
You can also pass in order-specific notes that will be displayed in the requisition form.
This can be achieved via the clinical_notes field in the Create Order endpoint.
What happens when both the Order and the Lab Account have a clinical note?
When this happens, Junction concatenates both of the notes, so they are always displayed.
Usage
Notes are new line separated (\n) strings. If you wish to provide more than one note, you can append a new line to your provided string. 
