Modifier 91, Repeat Clinical Diagnostic Laboratory Test, Is Used When

Modifier 91, Repeat clinical diagnostic laboratory test, is used when:

A) A patient presents with symptoms of hypoglycemia and is sent to the lab for a fasting blood glucose and then is sent back to the lab later on the same day to check on levels after treatment.
B) During the same encounter, a patient has a biopsy of a suspicious lesion on the forearm and an excision of a mole on the chest.
C) A provider sends the patient to a lab outside the clinic for testing. The lab has an agreement with the clinic to provide the service and will receive payment from the clinic.
D) After an open biopsy of a breast mass, the patient returns in the postoperative period for a total lumpectomy.