Ahhhh! This is an interesting topic.
Certain tests require Medicare medical necessity, meaning pt has a matching condition / diagnosis code.

This is part of the government’s requirement to ascertain that Medicare, which is paid for by our nation’s working contributors, is fairly charged. These policies are defined in National and Local Coverage Determinations (NCD, LCD) and are found on Medicare.gov. Medicare ads/deletes/updates policies and codes often.

If a test is not justified by a policy, patient should be given an Advance Beneficiary Notification (ABN) explaining this. If pt agrees and signs, pt will be billed. If pt refuses to sign but still wants the test, a witness signs to this effect, and pt will be billed. Or pt can refuse test.

Often clinician did not add pt’s justifiable dx code to the order. Sometimes the policy has complicated restrictions. Thus it is difficult for patients,, clinicians, providers, but it is a “necessity”.