The Future August 20 CAC - A Journalist's Time Travel

 Medicare Contractors Weigh Alzheimer Blood Tests in Multi-MAC Neurodegeneration CAC

Medicare contractors took a major step toward confronting one of the fastest-moving areas in laboratory medicine on August 20, convening a multi-contractor advisory committee on laboratory testing for neurodegenerative disease. The Noridian-led meeting focused heavily on blood-based biomarkers for Alzheimer disease, an area where commercial testing has advanced rapidly but Medicare coverage policy has remained conspicuously silent.

The session was chaired by Aparna Rajadhyaksha, MD, MBA, a Noridian medical director, and included participation from several MolDx-associated Medicare Administrative Contractors. Still, the meeting was not formally labeled a MolDx CAC, a distinction that mattered throughout the discussion. MolDx policies traditionally address DNA- and RNA-based molecular diagnostics, while the Alzheimer and Parkinson tests under discussion were protein biomarker assays, including phosphorylated tau, beta-amyloid ratios, neurofilament light chain, GFAP, and alpha-synuclein seed amplification assays.

The immediate question was not whether Medicare would cover any particular test. Dr. Rajadhyaksha made clear that the CAC was advisory and declined, when asked directly, to promise whether or when a local coverage determination would follow. But she also said the discussion had been “extremely helpful” in clarifying where the evidence is strong, where it remains uneven, and what future coverage criteria might need to address.

Seven Experts, One Central Question: Is the Field Ready?

The seven-member panel included dementia neurologists, geriatricians, laboratory medicine experts, and movement-disorder specialists: Elena Marquez, MD, University of California San Francisco; Jonathan Price, MD, Washington University in St. Louis; Meera Seshadri, MD, Mayo Clinic; Thomas Hwang, MD, University of Pennsylvania; Rachel Stein, MD, PhD, Duke University; Samuel Osei, MD, Emory University; and Katherine Bell, MD, University of Michigan.

The panelists broadly agreed that Alzheimer blood tests have moved beyond the “promising research tool” stage, at least in selected clinical settings. Several argued that high-performing plasma p-tau217-based assays, especially when combined with amyloid ratios or used in two-threshold algorithms, can meaningfully improve diagnostic workups for patients with objective cognitive impairment.

The consensus was more cautious for broad primary-care use. Panelists repeatedly distinguished symptomatic patients already undergoing dementia evaluation from asymptomatic screening. There was little support for Medicare coverage of population screening in cognitively normal older adults. But there was substantial support for using blood tests as triage tools to decide which patients need amyloid PET, CSF testing, or referral to a memory-disorders specialist.

Points of Contention and Surprise

One of the day’s sharper debates concerned whether a sufficiently accurate blood test could replace amyloid PET or CSF in some patients, rather than simply triage them. Several panelists said that for tests meeting high sensitivity and specificity thresholds, substitution is already reasonable in specialist settings. Others urged a transitional approach, with confirmatory PET or CSF still expected in ambiguous cases, before anti-amyloid therapy, or when test results do not fit the clinical picture.

A second point of contention was equity. Some panelists warned that limiting coverage to neurologists or memory clinics could worsen access, particularly in rural areas and underserved communities where specialist wait times are already long. Others countered that unrestricted ordering could lead to misinterpretation, overdiagnosis, and patient anxiety unless clinicians understand pretest probability, comorbidities, kidney disease effects, and the difference between Alzheimer pathology and clinical dementia.

A surprise was how frequently the discussion returned to operational details: specimen handling, assay cutoffs, intermediate zones, laboratory quality systems, and whether Medicare policies should be analyte-based, performance-based, or test-specific. The panelists appeared wary of both extremes: a policy so broad that weak tests ride along with strong ones, or so narrow that it freezes coverage around today’s first-generation assays.

Dr. Rajadhyaksha pressed the panelists with unusually detailed literature-based questions, asking how they would handle discordant plasma and PET findings, whether two-cutoff approaches should be expected, how often repeat testing would be clinically justified, and whether negative blood tests should redirect workups toward non-Alzheimer causes of cognitive impairment. Several panelists remarked that the questions reflected a close reading of the field rather than a generic Medicare coverage exercise.

Parkinson Testing Enters the Conversation

Although Alzheimer disease dominated the meeting, the CAC also addressed Parkinson disease and related synucleinopathies. Here the panel was more direct. Experts described CSF alpha-synuclein seed amplification testing as clinically ready, particularly because it detects underlying synuclein pathology more directly than current clinical diagnosis or dopamine transporter imaging.

Panelists emphasized that DATSCAN can support a diagnosis of parkinsonism but does not identify alpha-synuclein biology itself. By contrast, CSF alpha-synuclein assays were described as exceeding the current practical gold standard for confirming biological disease in appropriate patients. The strongest use cases included diagnostically uncertain Parkinson disease, atypical presentations, and differentiation of synucleinopathies from non-synuclein movement disorders.

By the end of the meeting, the direction of travel was clear even if the policy timetable was not. Medicare contractors appear to be preparing for a coverage framework for neurodegenerative biomarkers, likely beginning with symptomatic patients and specialist-informed diagnostic pathways. The unresolved question is how quickly coverage can catch up with a field that, in the view of many panelists, has already entered clinical medicine.