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

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

A) After an open biopsy of a breast mass, the patient returns in the postoperative period for a total lumpectomy.
B) 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.
C) 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.
D) 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.