The derivation is the process that allows refers a patient and asks for some kind of test to a centre.
It initiates a request for referral from the petitioner centre, after sending the message, the provider responds with another message. The petitioner centre may submit change or cancellation of the derivation and the provider centre can do it as well. Finally, the provider centre is responsible for terminating the process.
The package "Test Leads" contains everything regarding to managing a referral (to create a new one, modify, cancel, add another one and get the results).