Over the past year, a new kind of lab result has started arriving in our inboxes. Patients forward a p-tau217 value from a primary care visit, raw APOE data from a consumer genetics report, or an amyloid ratio they purchased online, and they want to know two things: what it means, and what they should do now.
Here’s what’s happened…fifteen months ago there were no FDA-cleared blood tests for Alzheimer’s disease. Today there are four, and two of them were cleared within the same week in August 2026. Brain health has become a primary care conversation, and functional medicine practitioners are often the clinicians’ patients seek out when they want a prevention plan rather than a wait-and-see answer.
This article walks through what the current literature supports, how to order and interpret these tests, how APOE4 status changes the conversation, what a prevention plan for an APOE4 carrier looks like, and an honest appraisal of whether the Bredesen ReCODE framework helps practitioners do this work well.
What Changed in the Testing Landscape
The FDA has now cleared four blood tests for Alzheimer’s disease, beginning with Fujirebio’s Lumipulse test in May 2025 [1-3]. They differ in method and age range, but all are intended for adults who already have cognitive symptoms. The one most practitioners will encounter is Roche’s Elecsys pTau217, cleared in August 2026, because it is the first test that can help both confirm and rule out Alzheimer’s pathology, and Quest and Labcorp plan to offer it nationally [3,4]. The table below summarizes each test, who it is intended for, and how to order it.
p-tau217 has displaced older markers because it performs well. In a large validation study spanning primary and specialty care, it identified Alzheimer’s pathology with roughly 85 to 94 percent accuracy, approaching the performance of spinal fluid testing, though a small share of patients fall into an intermediate zone that needs follow-up and accuracy is somewhat lower in patients over 80 [5]. It is also changing practice: in a 2026 study, primary care clinicians’ diagnostic accuracy rose from 65 to 93 percent once they had blood test results, nearly matching specialists, and a negative result was especially useful for ruling Alzheimer’s out [6].
Blood-Based Biomarker Test Menu
| Test | What it measures | Regulatory Status | Intended use | How to access |
|---|---|---|---|---|
| Lumipulse G pTau217/β-amyloid 1-42 ratio (Fujirebio) | p-tau217 to Aβ42 ratio, immunoassay | FDA cleared, May 2025 | Symptomatic adults; aid in assessing amyloid pathology | Through clinical laboratories running the Lumipulse platform |
| Elecsys pTau181 (Roche) | p-tau181, immunoassay | FDA cleared, 2025 | Primarily rule-out in primary care | Clinical laboratories with Roche cobas platforms |
| PrecivityAD2 (C2N Diagnostics) | %p-tau217 and Aβ42/40 combined score, mass spectrometry | FDA cleared, August 2026; cleared version expected later in 2026 | Symptomatic adults 40 and older | Clinician order through C2N; CLIA-validated version available now |
| Elecsys pTau217 (Roche) | p-tau217, single biomarker | FDA cleared, August 2026 | Symptomatic adults 55 and older; rule-in and rule-out | Quest (planned Q4 2026) and Labcorp (announced) |
| Quest AD-Detect and Labcorp p-tau217 | p-tau217; Quest also offers a panel combining Aβ42/40, p-tau217, and ApoE | Lab-developed tests, not FDA reviewed | Aid in evaluation of symptomatic patients | Clinician order; draw at patient service centers |
| Quest AD-Detect consumer test | Aβ42/40 ratio only | Lab-developed, consumer-initiated | Screening, not diagnostic | Not recommended as a standalone screen |
Blood-based Alzheimer’s biomarker tests available in the United States as of October 2026. Confirm current availability and intended-use labeling with the laboratory before ordering.
What the Guidelines Say and Their Limitations
The Alzheimer’s Association released its first clinical practice guideline on blood-based biomarkers in July 2025, built on GRADE methodology and written for specialists evaluating patients with objective cognitive impairment, meaning mild cognitive impairment (MCI) or dementia [7]. The guideline is brand-agnostic and performance-based. Tests with at least 90 percent sensitivity and 75 percent specificity can serve as triage tools, while tests reaching at least 90 percent for both can substitute for amyloid PET or cerebrospinal fluid testing as confirmatory tools. A good practice statement is explicit: blood biomarkers should not be ordered before a comprehensive clinical evaluation, and results must be interpreted in the context of that evaluation [7].
Equally important is what the guideline does not cover. It makes no recommendation for cognitively unimpaired individuals or for population screening, and the Association has stated plainly that those questions remain unanswered [8]. A primary care guideline is in development, and a dementia prevention guideline is planned for 2027 [9]. For now, any use of these tests in asymptomatic patients sits outside formal guidance.
Who to Test, and When
For a patient with cognitive complaints, the sequence is important. Start with a structured cognitive assessment (the MoCA or a validated digital tool), a medication review with attention to anticholinergic burden, and a workup for reversible and contributing factors: B12 and homocysteine, a full thyroid panel, CBC, CMP, A1c with fasting insulin, vitamin D, screening for depression, hearing and vision checks, and screening for obstructive sleep apnea. If objective impairment is present, that is the point at which a p-tau217 test belongs in the plan. Ordering the blood test first and building the evaluation around it reverses the logic the guideline was designed to protect. Now this sequencing is evolving as practitioners use the testing in practice more, I am sure more insight is soon to follow.
The cognitively unimpaired patient is where our field will feel the most tension. In July 2026, a JAMA study following 2,684 cognitively healthy older adults for up to 13.5 years found that those with high p-tau217 levels had a 38 percent risk of developing cognitive impairment within five years and a 78 percent risk within ten [10]. That is meaningful prognostic information, and prevention-minded patients will ask for it. Our position is that testing an asymptomatic patient can be reasonable, but only after pre-test counseling that covers what each result would mean, the absence of approved treatment for asymptomatic amyloid positivity outside clinical trials, the psychological weight of a positive result, and insurance implications. Consumer amyloid ratio tests should not be used as standalone screens; the direct-to-consumer AD-Detect product, for example, measures the Aβ42/40 ratio rather than p-tau217 and is labeled as a screening test rather than a diagnostic one [11].
Clinical Pearl: Before ordering p-tau217, write down what you will do with a positive, an intermediate, and a negative result. If the plan is identical for all three, the test is unlikely to add value for that patient right now.
Interpreting the Result and Next Steps
Most current p-tau217 reports return a three-tier result: positive, intermediate, or negative. A positive result in a symptomatic patient indicates a high likelihood of amyloid pathology. It supports Alzheimer’s disease as a contributor, but it does not exclude co-pathology, and it does not end the investigation. Next steps include referral to neurology or a memory clinic for diagnostic confirmation and staging, particularly if the patient wants to be evaluated for anti-amyloid therapy, along with APOE genotyping and a full contributor workup that continues in parallel.
An intermediate result calls for either repeat testing in six to twelve months or referral for confirmatory CSF or PET testing, depending on symptom trajectory and patient goals. Ratio-based assays such as percentage p-tau217 tend to produce fewer intermediate results [5]. A negative result in a symptomatic patient makes Alzheimer’s pathology less likely and should widen the differential: vascular contributions, Lewy body disease, frontotemporal syndromes, untreated sleep apnea, depression, medication effects, thyroid dysfunction, B12 deficiency, alcohol, and metabolic disease. This is territory where a systems-based workup earns its keep.
Two cautions apply to serial testing. Advanced age reduces accuracy, and body weight can shift plasma biomarker concentrations, so note age and BMI alongside any result, especially if a patient has lost significant weight. More importantly, p-tau217 has not been validated as a treatment-response marker. In the Bredesen randomized trial discussed below, cognition improved substantially in the intervention group while p-tau217 did not differ between groups [12]. Track function and cognition, not the biomarker alone.
APOE4: What the Genotype Does and Does Not Tell You
APOE4 remains the strongest genetic risk factor for late-onset Alzheimer’s disease, with two copies raising the odds up to 15-fold [13]. The 2024 Nature Medicine analysis by Fortea and colleagues reframed the homozygous state. Drawing on 3,297 brain donors and more than 10,000 living participants, the authors found near-complete penetrance of Alzheimer’s biology in APOE4 homozygotes: by age 65, more than 95 percent had abnormal CSF amyloid and 75 percent had positive amyloid scans, with symptom onset around age 65 [14]. They proposed that APOE4 homozygosity be considered a distinct, genetically determined form of Alzheimer’s disease, noting it affects roughly 2 to 3 percent of the population. Heterozygotes showed intermediate phenotypes and should not be counseled as though they carry the same risk [14].
To order APOE status, genotype testing is available through Quest, Labcorp, and Mayo Clinic Laboratories, and C2N offers a protein-based ApoE4 test. Quest has also launched a combined lab-developed panel that reports Aβ42/40, p-tau217, and ApoE together [4]. Consumer genetic results should be confirmed with a clinical test before they drive treatment decisions. Pre-test counseling matters here too. The Genetic Information Nondiscrimination Act protects against discrimination in health insurance and employment, but it does not extend to life, disability, or long-term care insurance, and patients deserve to know that before the result is in their chart. Homozygous results carry family implications, and a genetic counselor referral is appropriate.
APOE status also matters for safety if a patient is considering anti-amyloid therapy. The main risk of these drugs is brain swelling and small bleeds, known as ARIA, and that risk rises with each copy of APOE4. Roughly half of homozygotes in the lecanemab and donanemab trials developed ARIA, about double the rate seen on placebo [15,16], and in the EU and UK these drugs are not approved for homozygotes at all [17]. Both drug labels recommend genotyping before treatment, so for any APOE4 carrier we refer, that conversation should already have happened.
Clinical Pearl: APOE4 is a probability modifier, not a verdict. For heterozygotes, it is a reason to start comprehensive risk reduction earlier and pursue it more consistently. For homozygotes, the Fortea data justify treating prevention with the seriousness we bring to other inherited disease.
What a Functional Medicine Prevention Plan Looks Like for an APOE4 Carrier
The 2024 Lancet Commission estimates that 45 percent of dementia is potentially attributable to 14 modifiable risk factors, and it added two new ones recently: high midlife LDL cholesterol and untreated vision loss.
High LDL and hearing loss each account for an estimated 7 percent of cases, and the Commission recommends detecting and treating elevated LDL from around age 40 [18,19]. For APOE4 carriers, whose risk travels largely through lipid handling and vascular biology, that list is the scaffold of the plan. The functional medicine contribution is in how deeply each domain is assessed and how consistently the plan is delivered.
Vascular and lipid health. Go beyond LDL-C to ApoB, Lp(a), and, where risk is unclear, coronary imaging such as CT angiography to stratify vascular burden. Treat blood pressure to target; in SPRINT MIND, intensive blood pressure control reduced the risk of mild cognitive impairment [20]. Vascular risk reduction is brain risk reduction, and for carriers it should begin in midlife rather than after symptoms appear.
Metabolic health. Fasting insulin, HOMA-IR, and A1c identify insulin resistance years before glucose rises, and continuous glucose monitoring can reveal variability that fasting labs miss. In the Bredesen randomized trial, the intervention arm showed significant improvements in A1c and HOMA-IR alongside its cognitive gains [12].
Exercise and structured accountability. U.S. POINTER enrolled 2,111 at-risk older adults and compared a structured multidomain program with a self-guided version. Both improved global cognition, the structured arm improved more, and benefits held regardless of APOE4 status [21,22].
Sleep. Screen every carrier for sleep apnea, ideally with home sleep testing rather than symptom questionnaires alone. Sleep disruption is common, often unrecognized, and treatable.
Hearing and vision. Schedule formal hearing and eye exams and treat what is found. These are among the highest-yield, lowest-cost interventions on the Lancet list and are easy to overlook in a functional medicine workup.
Nutrition and omega-3s. APOE4 alters DHA handling; carriers given labeled DHA showed a 31 percent smaller rise in plasma levels than noncarriers [23]. Yet the PreventE4 trial, which gave high-dose DHA to 365 cognitively healthy adults with low fish intake, raised brain omega-3 levels without improving cognition or Alzheimer’s biomarkers, even among carriers. The investigator’s conclusion was that omega-3s matter, but a supplement alone is not sufficient [24]. Measure the omega-3 index, build intake through food first, and frame supplementation as one part of a broader dietary pattern.
Immune and infectious load. A natural experiment in Wales, where shingles vaccine eligibility was set by exact birth date, found that vaccination reduced new dementia diagnoses by 3.5 percentage points over seven years, roughly a 20 percent relative reduction, with a stronger effect in women [25]. That study used the live vaccine, so the effect of the recombinant vaccine on dementia is not yet known, but zoster vaccination is already indicated for most adults in this age group. By contrast, the VALAD trial randomized 120 HSV-seropositive patients with early Alzheimer’s disease to valacyclovir or placebo for 78 weeks and found no benefit; cognition actually declined slightly more in the treatment arm [26]. Routine antiviral therapy for cognition is not supported by current trial data but we do know empirically and in practice, that there is a strong correlation between post-viral syndrome and cognitive symptoms such as brain fog, slowed processing, and memory complaints. Large biobank studies support this. Severe viral infections are linked to higher rates of Alzheimer’s and other neurodegenerative diseases up to 15 years later, which makes preventing severe infection through shingles, influenza, and pneumonia vaccination the most actionable lever we have today
Hormonal transitions. For women, the menopause transition is a window in which vascular, metabolic, and neuroendocrine risk shift at once. The evidence on hormone therapy and dementia is observational and timing-dependent, and it does not yet justify prescribing hormones for dementia prevention alone. It does mean the brain belongs in every menopause risk-benefit conversation, especially for carriers. Individualized hormone protocols are covered in depth inside Functional Hormone Mastery.
Environmental and lifestyle exposures. Minimize alcohol, address air quality where possible, and evaluate toxicant or mold exposure when the clinical history supports it. The evidence here is largely associative, so prioritize these assessments when the story points toward them rather than ordering them reflexively.
Stratifying by genotype. For heterozygotes, begin comprehensive risk-factor optimization in midlife and establish a baseline cognitive assessment that is repeated over time. For homozygotes, start earlier, often in the 40s, with baseline cognitive testing, a discussion about biomarker testing after counseling, referral to a preventive neurology or memory program, and awareness of prevention trial registries. A repeated, validated cognitive measure will tell you more about how a patient is doing than serial biomarker values.
Where Does the Bredesen ReCODE Program Fit?
Dale Bredesen’s ReCODE model views Alzheimer’s disease as the result of many converging contributors, including insulin resistance, inflammation, hormonal and nutrient loss, toxic exposures, and infections. For functional medicine practitioners, that framing will feel familiar: it is essentially a systems-based approach applied with a focus on the brain. The evidence has built steadily, from early case reports and a 100-patient case series to a 25-patient pilot trial in which 84 percent of participants improved on cognitive testing over nine months [27-30].
The most important new data come from the first randomized trial, posted as a preprint and not yet peer reviewed [12]. Among 73 patients with MCI or early dementia, those on the personalized protocol improved substantially in overall cognition, memory, and executive function over nine months, along with better blood sugar, lipids, blood pressure, and weight, while the standard-care group did not. That is an encouraging signal, and it is also important to read the fine lines. Patients and clinicians knew who was receiving treatment, the intervention group received far more attention and support, and the design cannot tell us which components drove the benefit. Alzheimer’s blood biomarkers and brain volume did not differ between groups [12]. Dean Ornish’s 2024 randomized lifestyle trial points in the same direction, with improved cognition and function after just 20 weeks [31].
Our view is that ReCODE is most valuable as a framework rather than a protocol to follow line by line. Its real strength is evaluation discipline: systematically assessing metabolic, vascular, inflammatory, hormonal, nutrient, sleep, toxic, and infectious contributors in every patient with cognitive concerns, then delivering care with the coaching and accountability that POINTER showed makes a difference. Practitioners trained in functional medicine already have most of this toolkit; the framework brings it into focus for brain health. We can tell patients with confidence that improvement is possible in the early stages, while being clear that it is not guaranteed, leading with the most evidence-backed interventions and individualizing the rest.
Where the Evidence Leaves Room to Explore
Several questions remain open, and they are the ones our patients will keep asking. We do not yet know how best to use p-tau217 in cognitively unimpaired people, and the Alzheimer’s Association prevention guideline expected in 2027 will be an important marker. Whether serial p-tau217 can serve as a monitoring tool, and how to correct for weight change, is unresolved. APOE4-specific prevention, including how to deliver DHA to the brain effectively, deserves dedicated trials. A randomized trial of zoster vaccination for dementia prevention is being pursued. The combination of precision, multidomain care with disease-modifying therapy has not been tested, though the Bredesen authors raise it directly. And precision protocols still need blinded, adequately powered trials with component analysis before they can be called a standard of care.
Clinical Takeaway
Blood-based Alzheimer’s testing has moved from research to routine care in less than two years, and patients are arriving with results in hand. Our role is to put those results in sequence: evaluate before testing, interpret within the full clinical picture, refer when confirmation or disease-modifying therapy is on the table, and build prevention plans that start years before symptoms. For APOE4 carriers, that plan is vascular, metabolic, sensory, sleep-focused, and structured, and it is delivered with the same consistency the best trials used. That is where functional medicine is already strongest.
References
1. U.S. Food and Drug Administration. FDA clears first blood test used in diagnosing Alzheimer’s disease. News release. May 16, 2025.
2. Alzheimer’s Association. Statement on FDA clearance of PrecivityAD2 blood test for Alzheimer’s diagnosis in adults as young as 40. August 20, 2026.
3. Roche Diagnostics. Roche receives FDA clearance for Elecsys pTau217, advancing Alzheimer’s disease assessment across primary and specialty care. News release. August 24, 2026.
4. Quest Diagnostics. Quest Diagnostics to offer FDA-cleared Roche pTau217 blood test to assess Alzheimer’s disease pathology. News release. August 24, 2026.
5. Palmqvist S, Warmenhoven N, Anastasi F, et al. Plasma phospho-tau217 for Alzheimer’s disease diagnosis in primary and secondary care using a fully automated platform. Nat Med. 2025;31(6):2036-2043. doi:10.1038/s41591-025-03622-w. PMID: 40205199.
6. Palmqvist S, et al. Effects of Alzheimer’s disease blood-based biomarkers on diagnosis and clinical management in secondary and primary care. Presented at: Alzheimer’s Association International Conference; July 2026; London, UK.
7. Palmqvist S, Whitson HE, Allen LA, et al. Alzheimer’s Association clinical practice guideline on the use of blood-based biomarkers in the diagnostic workup of suspected Alzheimer’s disease within specialized care settings. Alzheimers Dement. 2025. doi:10.1002/alz.70535. PMID: 40729527.
8. Meglio M. NeuroVoices: Rebecca Edelmayer, PhD, on the Alzheimer’s Association’s new blood-based biomarker guidelines. NeurologyLive. September 24, 2025.
9. Alzheimer’s Association. Alzheimer’s Association releases its first clinical practice guideline for blood-based biomarker tests. AAIC press release. July 29, 2025.
10. Buckley RF, et al. Prognostic value of blood-based p-tau217 levels for progression to cognitive impairment. JAMA. Published online July 2026. doi:10.1001/jama.2026.12556.
11. Quest Diagnostics. Quest introduces first-to-market consumer-initiated blood test for Alzheimer’s disease risk assessment on questhealth.com. News release. July 31, 2023.
12. Toups K, Tanio CP, Hathaway A, et al. Precision medicine treatment of Alzheimer’s disease: successful randomized controlled trial. Preprints.org. Posted December 2025; version 3 April 20, 2026. doi:10.20944/preprints202512.2694.v3. Not peer reviewed.
13. Alzheimer Europe. APOE4 homozygosity causes a distinct, genetic form of Alzheimer’s disease, according to a new study. May 7, 2024.
14. Fortea J, Pegueroles J, Alcolea D, et al. APOE4 homozygozity represents a distinct genetic form of Alzheimer’s disease. Nat Med. 2024;30(5):1284-1291. doi:10.1038/s41591-024-02931-w. PMID: 38710950.
15. Eisai Inc. LEQEMBI (lecanemab-irmb) prescribing information, including Boxed Warning.
16. Eli Lilly and Company. What was the incidence of ARIA in Kisunla (donanemab-azbt)-treated participants by APOE genotype? Lilly Medical Information; KISUNLA prescribing information.
17. Sato K, Niimi Y, Kurihara M, Ihara R, Iwata A, Iwatsubo T. Utility of APOE testing for reducing ARIA under probabilistic stopping rates to treat with anti-amyloid therapy for ε4-homozygote patients: a simulation study. JAR Life. 2026;15:100059. doi:10.1016/j.jarlif.2026.100059. PMID: 41630792.
18. Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. Lancet. 2024;404(10452):572-628. doi:10.1016/S0140-6736(24)01296-0.
19. Alzheimer Europe. 2024 Lancet Commission underscores the potential for dementia risk reduction, identifying 14 modifiable risk factors across the life course. July 31, 2024.
20. SPRINT MIND Investigators; Williamson JD, Pajewski NM, Auchus AP, et al. Effect of intensive vs standard blood pressure control on probable dementia: a randomized clinical trial. JAMA. 2019;321(6):553-561. doi:10.1001/jama.2018.21442.
21. Baker LD, Espeland MA, Whitmer RA, et al. Structured vs self-guided multidomain lifestyle interventions for global cognitive function: the US POINTER randomized clinical trial. JAMA. Published online July 28, 2025. doi:10.1001/jama.2025.12923.
22. Alzheimer’s Association. U.S. POINTER study results. alz.org/us-pointer/study-results.
23. Yassine HN, Arellanes IC, Mazmanian A, et al. Baseline findings of PreventE4: a double-blind placebo controlled clinical trial testing high dose DHA in APOE4 carriers before the onset of dementia. J Prev Alzheimers Dis. 2023;10(4):810-820. doi:10.14283/jpad.2023.77.
24. Yassine HN, et al. CNS target engagement of high-dose DHA supplementation in older adults at risk for dementia: a randomised, double-blind, placebo-controlled trial. eBioMedicine. 2026. doi:10.1016/j.ebiom.2026.106316.
25. Eyting M, Xie M, Michalik F, Hess S, Chung S, Geldsetzer P. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature. 2025;641(8062):438-446. doi:10.1038/s41586-025-08800-x.
26. Devanand DP, Wisniewski T, Razlighi Q, et al. Valacyclovir treatment of early symptomatic Alzheimer disease: the VALAD randomized clinical trial. JAMA. 2026;335(6):511-522. doi:10.1001/jama.2025.21738. PMID: 41405855.
27. Bredesen DE. Reversal of cognitive decline: a novel therapeutic program. Aging (Albany NY). 2014;6(9):707-717.
28. Bredesen DE, Sharlin K, Jenkins D, et al. Reversal of cognitive decline: 100 patients. J Alzheimers Dis Parkinsonism. 2018;8:1-6.
29. Toups K, Hathaway A, Gordon D, et al. Precision medicine approach to Alzheimer’s disease: successful pilot project. J Alzheimers Dis. 2022;88(4):1411-1421.
30. Bredesen DE, Toups K, Hathaway A, et al. Precision medicine approach to Alzheimer’s disease: rationale and implications. J Alzheimers Dis. 2023;96:429-437. doi:10.3233/JAD-230467.
31. Ornish D, Madison C, Kivipelto M, et al. Effects of intensive lifestyle changes on the progression of mild cognitive impairment or early dementia due to Alzheimer’s disease: a randomized, controlled clinical trial. Alzheimers Res Ther. 2024;16:122. doi:10.1186/s13195-024-01482-z.
