A familial Alzheimer's genetic panel sequences three genes — PSEN1, PSEN2, and APP — and finds a pathogenic variant in roughly 60-80% of early-onset familial cases, with that detection rate falling as age of onset rises, according to ARUP Laboratories' test documentation. For adults over 65, that lower sensitivity matters: the panel was built for early-onset disease, and a negative result at this age carries more uncertainty than it would in a 45-year-old from a known mutation-carrying family. This guide covers what the panel can and cannot tell an older adult, how it differs from APOE testing, what preparation and counseling look like, and how a result can affect eligibility for newer Alzheimer's drugs.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What does this panel actually test, and how accurate is it?
- How is this different from APOE testing?
- Who should actually get the familial panel at this age?
- What does preparation and counseling actually involve?
- Frequently Asked Questions
What does this panel actually test, and how accurate is it?
The panel sequences PSEN1, PSEN2, and APP, the three genes tied to autosomal-dominant, early-onset familial Alzheimer's. Among people who do carry a pathogenic familial variant, PSEN1 accounts for roughly 20-70% of cases, APP for 10-15%, and PSEN2 for about 5% — while 20-40% of familial early-onset cases have no identifiable cause on any of these three genes, according to ARUP Laboratories. That gap matters for a negative result. The sequencing method used can miss regulatory and deep-intronic variants and may not detect large deletions, duplications, or insertions, so a clean panel does not rule out a heritable cause, per the same ARUP documentation.
For someone over 65 with a strong family history of early-onset dementia, a negative result means the three known genes were not implicated — not that the family's disease has no genetic basis. Penetrance also differs by gene. PSEN1 mutations are considered fully penetrant, meaning nearly every carrier eventually develops the disease, while PSEN2 mutations show reduced penetrance, cited at about 95%, according to South Carolina Blue Cross medical policy. A positive PSEN1 result in an older relative of an affected family member carries a different practical weight than a PSEN2 finding.
How is this different from APOE testing?
APOE is a separate gene, and it works differently from PSEN1, PSEN2, and APP. It is a risk-modifying gene, not a deterministic one: carrying the ε4 allele raises the odds of developing both early- and late-onset Alzheimer's, but it does not confirm or rule out the disease the way a PSEN1 or APP mutation can, according to a payer medical policy summary. This distinction matters most for adults over 65, because APOE testing has a newer, practical use that has nothing to do with family history. For patients considering anti-amyloid drugs, the FDA's labeling for lecanemab (brand name Leqembi) recommends APOE genotyping before starting treatment, to help estimate the risk of ARIA — amyloid-related imaging abnormalities, a swelling or bleeding side effect seen on brain scans — as reported in NeurologyLive's 2025 commentary on anti-amyloid therapy eligibility.
US labeling still allows treatment without the test, which leaves a patient's homozygote status, and their individual ARIA risk, unknown. Outside the US, the test is effectively required rather than optional. Regulators in the EU and UK have not approved lecanemab or donanemab for patients who carry two copies of the ε4 allele, so APOE genotyping becomes a gatekeeping step before treatment can start in those markets, per the same NeurologyLive report. A patient weighing anti-amyloid treatment should ask specifically whether APOE testing — not the PSEN1/PSEN2/APP panel — is the test their care team needs.
Who should actually get the familial panel at this age?
The familial panel is built around autosomal-dominant, early-onset disease, and professional guidance reflects that focus. The 2011 ACMG/National Society of Genetic Counselors practice guideline states the test is most appropriate for families with a documented history of early-onset Alzheimer's, and recommends it proceed only with support from someone with genetic counseling expertise in the field, according to a summary of the guideline published by Newswise. For an adult over 65 without that family history, the panel is a narrower tool than it might sound.
The Alzheimer's Association's official position holds that routine genetic testing of healthy, asymptomatic people for dementia risk should not proceed without prior genetic counseling to explain what a result would mean, and that broader susceptibility or risk testing is primarily valuable in research or clinical-trial settings rather than routine care, per the Alzheimer's Association's Genetic Testing Statement. In practice, this points toward a specific candidate: someone over 65 whose siblings, parents, or children developed Alzheimer's at an unusually young age, where identifying a PSEN1, PSEN2, or APP mutation would clarify risk for the patient's own children or grandchildren. An adult with no such family pattern, who is mainly curious about general dementia risk, is better served by the APOE conversation in Section 2 or by a clinical workup for symptoms already present.
What does preparation and counseling actually involve?
Genetic counseling is not a formality attached to the test — it is where the result gets interpreted. A 2025 presentation to a Wisconsin dementia-care network, delivered by genetic counselor Abigail Freeman, outlined what that process typically looks like for patients and families: a counselor walks through family history, explains what a positive, negative, or inconclusive result would mean, and discusses who else in the family might need to know, according to the presentation materials. Cost and timing are concrete enough to plan around.
The same presentation cites a typical panel cost around $300, with a range of roughly $0 to $1,000 depending on insurance coverage, and a turnaround time of about three weeks for results. A patient scheduling this test should ask their insurer in advance whether genetic counseling and the panel itself are covered separately, since the two are often billed apart. Before the blood draw, it helps to arrive with a written family history: ages of onset, which relatives were affected, and whether any relative has already tested positive for a specific mutation. That history is what lets the counselor and lab interpret a result accurately, and it is also the detail the ACMG/NSGC guideline in Section 3 treats as the deciding factor in whether testing is appropriate at all.
- Confirm with your insurer whether the counseling visit and the panel are billed as one service or two.
- Bring a written record of relatives' ages at diagnosis, not just "early-onset" in general terms.
- Ask directly whether a negative result would be followed by any additional testing, such as looking for large deletions or duplications the standard panel can miss.
- If anti-amyloid treatment is the real reason for testing, confirm with the prescribing clinician whether APOE genotyping, not the familial panel, is the test actually needed.
Frequently Asked Questions
Can a negative result on this panel rule out a genetic cause of Alzheimer's in my family?
No. The sequencing method can miss regulatory and deep-intronic variants and certain large structural changes, so a negative result leaves those possibilities open, according to ARUP Laboratories' test documentation.
If I only want to know my general Alzheimer's risk, is this the right test?
Likely not. This panel targets early-onset familial mutations; the Alzheimer's Association states that general risk testing in healthy adults is primarily useful in research settings, not routine care.
Does a positive PSEN2 result mean I will definitely develop Alzheimer's?
Not necessarily. PSEN2 shows reduced penetrance, cited at about 95%, unlike PSEN1, which is considered fully penetrant, per South Carolina Blue Cross medical policy.
