Medicare ABN for Genetic Tests: What Labs Must Know About GA and GZ Modifiers
Short answer: A Medicare Advance Beneficiary Notice (ABN, CMS-R-131) lets a lab bill a patient for a genetic test Medicare is expected to deny, but only if the notice is issued, the patient is told Medicare may not pay, and the patient signs. Without all three, the lab can be held liable and cannot collect from the patient.
Why ABNs matter more for genetic testing labs now
Molecular coverage is increasingly set by local policy. Noridian's MolDX notice states that two LCDs, L40242 (Genetic Testing for Hereditary Thrombophilia) and L40222 (Non-NGS Targeted Molecular Panel Tests for Targeted Therapy in Cancer), were finalized with an effective date of October 12, 2026. When a test falls outside the covered indications in a policy like these, the lab faces an expected denial. The ABN is the tool that decides who pays for it: the lab or the patient.
This guide is for lab compliance and revenue cycle teams. For the coverage rules themselves, see our breakdown of the MolDX non-NGS cancer panel LCD.
When an ABN is required
According to the CMS MLN booklet on Medicare Advance Written Notices of Non-coverage, all fee-for-service Medicare providers and suppliers must issue an ABN when they expect a denial that shifts liability to the patient. The booklet lists Part B items and services from independent labs among the situations where the ABN applies.
The trigger is an expected denial. CMS also explains that Medicare will not pay for a usually covered service if the provider knew or should have known it was not reasonable and necessary for that patient. That is the standard a lab applies when it reviews a requisition against an LCD or NCD.
Who can issue the notice
CMS defines notifiers to include physicians, practitioners, health care providers including labs, and suppliers. When the ordering and delivering providers differ, as when a physician orders a test that an independent lab performs, any notifier involved in delivering care can issue the notice. Multiple notifiers can be listed in the form's header if the patient can tell whom to contact about billing. CMS says the billing notifier is held responsible for issuing the notice.
For genetic labs, this means your contract with referring practices should state who delivers the ABN, and your billing team should confirm it exists before the claim goes out. Our guide to Medicare lab test order requirements covers the companion documentation.
Routine notices are prohibited
A common mistake is having every patient sign an ABN at intake. CMS states routine notices are not permitted, with defined exceptions. Per the MLN booklet, the exceptions include experimental items and services, items with frequency limits set by statute, regulation, NCDs or LCDs, and medically unnecessary services that are always denied. A genetic test with a frequency limit in an LCD may qualify; a blanket form signed by every patient does not.
Completing the notice correctly
The booklet sets out the following requirements for completion: the patient or representative must select an option before signing, and must sign and date the notice. The notice cannot exceed one page. For electronic notices, you must offer a paper copy and keep a copy for your records. If the patient refuses to choose an option or sign, you note the refusal on the original.
Retention is five years from the date of care delivery when no other state law applies. CMS says records must include cases where the patient declined care, refused an option, or refused to sign. Build this into your document retention schedule alongside requisitions and test reports.
Claim modifiers: GA, GX, GY and GZ
The ABN is only half the process. The claim must report what happened, using the modifiers in the MLN booklet:
GA means a waiver of liability statement was issued as required. Keep the ABN on file and make it available on request. Use GA when covered and non-covered services appear on the same claim. GZ reports an expected denial as not reasonable and necessary where no ABN was issued. GX is a voluntary notice of liability for a service Medicare never covers. GY reports an item or service that is statutorily excluded or not a Medicare benefit. GX can be used with GY or separately.
Modifier errors also create duplicate and denial problems elsewhere on the claim; see Medicare duplicate lab test denials and modifier 91.
A practical lab checklist
Review high-risk test and diagnosis pairs against active LCD and NCD criteria before billing. Decide, in writing, who issues the ABN: the lab, the ordering practice, or both. Use the standardized approved form and keep it to one page. Capture the patient's option selection, signature and date. Record any refusal on the original. Report GA or GZ accurately on every affected line. Retain the record for five years. Finally, audit a sample monthly to confirm that notices are not being issued routinely, since that practice is not permitted.
For a wider view of why these claims fail, read our guide to genetic testing denials, and learn how ScreenMyGene supports coverage and documentation workflows for labs.
Frequently asked questions
Can a genetic testing lab issue its own ABN?
Yes. CMS lists labs among the notifiers that can issue an ABN, and when the ordering and delivering providers differ, any notifier involved in delivering care can issue it. The billing notifier is held responsible for making sure the notice is issued, so labs should confirm delivery rather than assume it.
What happens if the patient refuses to sign?
CMS says to note the refusal on the original notice and keep it in your records. Liability shifts only after the notice is issued, the patient is told Medicare may not pay, and the patient signs. A refusal means the shift to the patient has not been secured.
Can we use one ABN for every patient?
No. CMS says routine notices are not permitted, apart from specific exceptions such as experimental services and items with frequency limits set by statute, regulation, NCDs or LCDs. Issue the notice when you expect a denial for that patient and that service.
When do we use modifier GZ?
Use GZ when you expect Medicare to deny a service as not reasonable and necessary and no ABN was issued. CMS notes that you may be held liable, and cannot collect from the patient, if you did not issue a required notice or your MAC finds it invalid.
How long must ABN records be kept?
Five years from the date of care delivery, when no other state law requirement applies. Records should include cases where the patient declined care, refused an option, or refused to sign, according to the CMS MLN booklet.
This article is for educational purposes only and is not legal, billing or medical advice. Coverage and billing rules change; confirm requirements with your Medicare Administrative Contractor and qualified counsel.
Sources: CMS MLN, Medicare Advance Written Notices of Non-coverage; Noridian Medicare, MolDX LCDs finalized effective October 12, 2026.