Ask whether your family history fits early-onset disease, who should give DNA first, what counseling involves, and what results can change. An APP gene test checks for harmful changes in the APP gene, a cause of Alzheimer's that begins before age 65. Most Alzheimer's is late-onset and sporadic. According to the Alzheimers.gov genetics fact sheet, early-onset disease is less than 10% of all Alzheimer's, and only 10–15% of those early cases are linked to APP, PSEN1, or PSEN2 changes Alzheimer's disease genetics fact sheet.
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
- Does our family history fit APP testing?
- Who should give DNA first?
- What safeguards come with predictive testing?
- What can results change — and what can't they?
Does our family history fit APP testing?
Ask what ages relatives developed symptoms and how many generations were affected. APP variants cause Alzheimer's before age 65, MedlinePlus Genetics reports, but they account for less than 10% of early-onset cases.
Ask whether the pattern looks autosomal-dominant. The NIA genetics fact sheet reports that APP, PSEN1 on chromosome 14, and PSEN2 on chromosome 1 act this way, so each child of a carrier has a 50% chance of inheriting the variant. A pedigree with early memory loss in a parent and grandparent raises the question more strongly than one late-onset case.
Who should give DNA first?
Ask if an affected relative can test before you do. Clinical APP testing is usually offered as a three-gene panel with PSEN1 and PSEN2, and the joint ACMG and NSGC guidelines recommend testing an affected family member first to find the familial variant joint ACMG-NSGC testing guidelines.
That order matters because a clear result in someone with symptoms gives the family a target. Without a known family variant, your own negative result leaves more uncertainty. Ask the clinic which relative is the best candidate and whether stored DNA or records can help if that person cannot test.
What safeguards come with predictive testing?
Ask what counseling, consent, and support the program requires. The joint ACMG and NSGC guidelines require predictive APP testing to include formal genetic counseling, pedigree risk review, separate pre-test and post-test visits, and a support person present.
Use the pre-test visit to ask practical questions: Bring the support person to both visits. Discuss insurance, privacy, work effects, and how you would handle either result before blood is drawn.
- How will you use my pedigree and medical history to estimate risk?
- What are the possible results, including uncertain findings?
- Who will disclose results, and who else will see them?
- What follow-up and family communication help do you offer?
What can results change — and what can't they?
Ask what a positive, negative, or uncertain result would mean for care and family planning. A negative APP result is not definitive when no family mutation is known and does not rule out Alzheimer's, Genetics Education Canada summarizes, because most disease is sporadic or involves undiscovered genes Alzheimer disease testing summary. Ask about timing limits and related genes.
The ACMG and NSGC guideline review reports variable expression, with onset varying by more than 20 years even within one family, so a positive result cannot set an exact onset age. Also ask why the clinic is not ordering APOE-e4 instead, since ACMG Choosing Wisely describes APOE-e4 as a risk factor that is neither necessary nor sufficient for dementia and advises against ordering it as a predictive test. Request a written plan for sharing results with at-risk relatives.
