Last month, we discussed the importance of establishing medical necessity prior to ordering or performing any special ophthalmological tests on a patient with diabetes.

With the focus of this month’s issue being on new technology and diagnostic testing, let’s revisit the topic of the Advanced Beneficiary Notice of Noncoverage (ABN) and how it applies when you suspect that a procedure or test may not be paid for by the carrier.

Know When You Need an ABN
Every doctor should know the importance of issuing an ABN to a Medicare patient. And, by the end of this column, you’ll know which of the four modifiers—GA, GX, GY or GZ—is most appropriate to append to the CPT code of the procedure or test in question.

When a provider thinks that Medicare will not pay for some or all of the services or items, the ABN is a written notice that the provider gives to the Medicare beneficiary before those items or services are furnished. The ABN is a formal document required by Medicare, but the concepts here often apply to other commercial medical carriers as well. (The most current ABN form and instruction set can be downloaded at www.cms.gov/Medicare/Medicare-General-Information/BNI/ABN.html.)

There are four common modifiers that can be appended to the CPT codes for procedures that may be denied by the carrier. Depending on the service provided and specific circumstances, the modifier may be required by Medicare or voluntarily appended to the CPT code.

Modifiers for an ABN
GA. Modifier GA indicates that the ABN is required by the payer policy. It is appended to a CPT code to report that a required ABN was issued for a service and is on file. If the service is denied, CMS will assign financial liability to the beneficiary. Because ABN was properly obtained, the financial liability is legally transferred to the patient and the physician can bill the patient for this service.

GX. When modifier GX is appended to a CPT code, it used to report that a voluntary ABN was issued for a service that is statutorily excluded from Medicare reimbursement. Medicare rejects non-covered services appended with GX and assigns liability to the beneficiary. Because this is a voluntary ABN, the patient always has financial responsibility for the procedure or test being conducted.

GZ. Modifier GZ indicates that a service or item is expected to be denied as unreasonable or unnecessary. It is appended to a CPT code to report that an ABN was not issued for this service. CMS will automatically deny these services and indicate that the beneficiary is not responsible for payment. Because the doctor did not obtain an ABN prior to performing the service, he cannot bill the patient.

GY. Modifier GY is appended to a CPT code to report when a service is specifically excluded by Medicare and an ABN was not issued to the beneficiary. This indicates that the service is statutorily excluded or does not meet the definition of any Medicare benefit. CMS will deny these claims and the beneficiary will be totally responsible for all financial liability.

Modifiers GA and GZ are used, for example, if a procedure does not meet medical necessity as determined by a Medicare Local Coverage Determination (LCD) or National Coverage Determination (NCD), or occurs more frequently than stipulated in your carrier’s guidelines.

Modifiers GX and GY are used for items or services statutorily excluded from the Medicare program. Here, the use of an ABN is optional, but provides proof that the beneficiary understands he will be liable for payment for these services. In other words, modifiers GX and GY are informational only. When using either modifier, the provider should bill the patient for the services provided.


Understanding how to use an ABN will allow you to incorporate new technologies into your practice and provide the highest level of care to your patients without having to be financially at risk. Knowing which modifier to use in the appropriate case will save you time and make you money.

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