(200) Fragmented access to Alzheimer’s plasma biomarkers: A Medicaid policy review of coverage for early detection and anti-amyloid therapy eligibility

Background: : Plasma biomarkers including phosphorylated tau (pTau-181), amyloid beta 42/40 ratio (Aβ42/40), glial fibrillary acidic protein (GFAP), and neurofilament light chain (NfL) are transforming Alzheimer’s disease (AD) diagnostics by enabling earlier, less invasive confirmation of amyloid pathology. Their relevance has grown with the approval of anti-amyloid monoclonal antibodies requiring biomarker evidence prior to treatment. However, Medicaid coverage remains fragmented, raising concerns about delayed diagnosis, inefficiencies, and restricted access, particularly among racially and ethnically minoritized populations disproportionately affected by AD.

Objective: : To evaluate Medicaid coverage of plasma-based AD biomarkers across all 51 jurisdictions and assess alignment with therapy eligibility. The review also assessed CPT-based coverage clarity, reimbursement structure, and attention to health equity.

Methods: : A systematic review of Medicaid policies was conducted in accordance with PRISMA 2020 guidelines (January 2022 to May 2025). Sources included state Medicaid websites, CMS portals, and policy bulletins. Inclusion required references to plasma biomarkers, CPT codes (e.g., 0346U for Aβ42/40, 0412U for pTau-181, 0443U for NfL), or diagnostic criteria for therapy approval. Coverage was classified as explicit (biomarker named with CPT and billing guidance), partial (biomarker named without CPT/billing), or absent. Two reviewers independently extracted and validated data. Equity was defined as any mention of disparities or targeted access.

Results: : Among 51 jurisdictions, 18 (35%) referenced at least one plasma biomarker. Eleven (22%) included CPT codes, primarily for Aβ42/40 or pTau-181. Nine (18%) required biomarker evidence for therapy approval, while 72% permitted cerebrospinal fluid (CSF) or PET testing through existing benefits. Seventeen states (33%) limited plasma testing to select labs, often CLIA-certified or manufacturer-designated. Only six jurisdictions (12%) referenced health equity, and fewer than 10% addressed plasma assays in diagnostic stewardship. Ambiguities in benefit designation and lack of federal standards contributed to inconsistent reimbursement.

Conclusions: : Medicaid coverage for plasma-based AD biomarkers remains inconsistent and misaligned with treatment eligibility criteria. Delays in diagnostic access and uneven reimbursement reflect broader gaps in coverage infrastructure. Federal guidance, CPT standardization, and equity-focused reforms are needed to improve early detection and reduce disparities in AD care.

Sponsorship:: None