Alzheimer’s disease affects millions of older adults globally. Accurate diagnosis is paramount for effective care management, especially with new treatments targeting the disease’s underlying biology. Advanced medical imaging, particularly Positron Emission Tomography (PET) scans, provides insight into the changes occurring in the brain. These scans visualize biological processes, helping physicians confirm a diagnosis or rule out other causes of cognitive decline. Understanding Medicare coverage for these diagnostic tools is important for patients and families.
Types of PET Scans Used for Alzheimer’s Diagnosis
Two main types of PET scans investigate cognitive impairment and Alzheimer’s disease pathology, focusing on different biological markers.
FDG-PET Scans
The Fluorodeoxyglucose-PET scan, known as FDG-PET, measures metabolic activity in the brain. This scan uses a radioactive glucose tracer to visualize how brain cells utilize sugar. In Alzheimer’s disease, a characteristic pattern of decreased glucose uptake (hypometabolism) appears in specific brain regions, helping physicians distinguish it from normal aging or other forms of dementia.
Amyloid PET Scans
The Amyloid PET scan detects amyloid-beta plaques in the brain, which are defining pathological hallmarks of Alzheimer’s disease. Amyloid PET tracers bind directly to these protein deposits, confirming the presence of this specific pathology. This imaging technique is considered the gold standard for confirming the biological diagnosis of Alzheimer’s and is relevant for determining eligibility for new anti-amyloid treatments.
Medicare’s Specific Coverage Criteria
Medicare Part B covers medically necessary diagnostic services, including PET scans. The specific coverage rules for Alzheimer’s imaging recently underwent a major change.
Amyloid PET Coverage
Historically, coverage for Amyloid PET scans was severely restricted by the Centers for Medicare & Medicaid Services (CMS) via a National Coverage Determination (NCD 220.6.20). This NCD limited coverage to a single scan per lifetime and only for patients enrolled in specific clinical trials.
In October 2023, CMS retired this restrictive NCD. This policy shift ended the clinical trial requirement and the once-per-lifetime limit, allowing broader access. Coverage determinations are now made by local Medicare Administrative Contractors (MACs) based on clinical necessity. This change was driven by the FDA approval of new anti-amyloid treatments, such as Leqembi, which require confirmation of amyloid pathology for effective use.
FDG-PET Coverage
Coverage for FDG-PET scans for dementia diagnosis is governed by a separate, established NCD (220.6.13). This scan is considered necessary for patients with documented cognitive decline for at least six months and a recently established dementia diagnosis. The primary role of the FDG-PET scan is for the differential diagnosis of Alzheimer’s disease and frontotemporal dementia (FTD) when the cause of symptoms is uncertain after a thorough initial evaluation. The physician must document that the scan is necessary to distinguish between two possible diagnoses, as coverage is not granted for a general dementia diagnosis.
Patient Financial Obligations
When a PET scan is approved for coverage, the cost-sharing structure for Original Medicare (Part A and Part B) beneficiaries is straightforward. The procedure falls under Medicare Part B, covering outpatient services and diagnostic tests. After the patient meets the annual Part B deductible, Medicare pays 80% of the approved amount.
The patient is responsible for the remaining 20% coinsurance. This out-of-pocket cost for a covered PET scan typically ranges from $200 to $300. Beneficiaries with a Medigap (Medicare Supplement) policy usually have this 20% coinsurance covered, minimizing their expense for the service.
Medicare Advantage (Part C) beneficiaries have a different financial experience, as these plans are offered by private insurance companies. The patient’s cost-sharing—which may be a fixed copayment or a percentage coinsurance—depends on the specific plan’s structure and network requirements. Patients must consult their plan documents to determine the exact deductible, copayment, or coinsurance amounts. Total cost exposure is capped by the plan’s annual out-of-pocket maximum, a financial protection not offered by Original Medicare alone.
Securing Authorization and Handling Denials
The process for obtaining a covered PET scan begins with the referring physician, who must ensure the patient meets Medicare’s specific coverage criteria and document medical necessity. For Original Medicare beneficiaries, the local Medicare Administrative Contractor (MAC) determines final coverage. For Medicare Advantage enrollees, the plan manages the authorization process. Prior authorization is often necessary for expensive imaging services, requiring the provider to submit documentation before the scan.
Advance Beneficiary Notice of Noncoverage (ABN)
If a provider believes Medicare may deny the claim because the service is not medically necessary under the coverage rules, they must issue an Advance Beneficiary Notice of Noncoverage (ABN). This standardized form informs the patient that they may have to pay if Medicare denies the claim. By signing the ABN, the patient accepts financial responsibility if denied, but preserves the right to appeal.
The Appeals Process
If Medicare or a Medicare Advantage plan denies coverage after the service, the patient has the right to file an appeal. The appeal process involves several levels of review, starting with a request for reconsideration detailed on the Medicare Summary Notice (MSN) or the plan’s Explanation of Benefits (EOB). Successfully appealing a denial requires providing additional physician documentation that clearly demonstrates the service met the specific medical necessity and coverage criteria.