Patients asking about APOE gene test results? Here’s what to tell them
This guidance can help shape the conversations you have with patients who want to understand the results of their gene and biomarker testing for Alzheimer disease.
The ε2/ε4 genotype is rare. One study showed that in healthy adults, the frequency was 7 in 210 (0.02 [0.01-0.04]).34 Given the rarity of the ε2/ε4 genotype, data about it are sparse. However, since the ε4 allele increases risk but the ε2 allele decreases risk, it is likely that any increase in risk is more modest than with ε3/ε4. In addition, it would help Mr. L to know that AD occurs infrequently before age 60.35 Given his relatively young age, he is unlikely to develop AD any time in the near future. In addition, particularly if he starts early, he might be able to mitigate any increased risk through some of the advice provided to Mr. K in Vignette 5.
Vignette 7
Joe J, age 65, comes to the clinic for a new patient visit. He has no concerns about his memory but has a family history of dementia and recently purchased DTC genetic testing to learn about his genetic health risks. His results showed an APOE ε4/ε4 genotype. He is concerned about developing AD. He heard on the news that there is a drug that can treat AD and wants to know if he is a candidate for this treatment.
Mr. J would benefit from the education provided to Ms. W in Vignette 1. Patients such as Mr. J should be advised that while an APOE ε4/ε4 genotype conveys an increased risk for AD, it is not deterministic of the disease. While there are no specific preventive measures or treatments based on APOE genotype, careful medical care and lifestyle factors can offset some of the risk (see Vignette 5 for discussion).
Recently (and controversially), the FDA approved aducanumab, a drug that targets amyloid.6,36 Of note, brain amyloid is more common in individuals with the APOE ε4/ε4 genotype, such as Mr. J. However, there would be no point in testing Mr. J for brain amyloid because at present the drug is only indicated in symptomatic individuals—and, even in this setting, it is controversial. One reason for the controversy is that aducanumab has potentially severe adverse effects. Patients with the ε4/ε4 genotype should know that this genotype carries increased risk for the most serious adverse event, ARIA—which can include brain edema and microhemorrhages.
What lies ahead?
More research is needed to explore the impact that greater AD gene and biomarker testing will have on the health system and workforce development. In addition, graduate schools and training programs will need to prepare clinicians to address probabilistic risk estimates for common diseases, such as AD. Finally, health systems and medical groups that employ clinicians may want to offer simulated training—similar to the vignettes in this article—as a practice requirement or as continuing medical education. This may also allow health systems or medical groups to put in place frameworks that support clinicians in proactively answering questions for patients and families about APOE and other emerging markers of disease risk.
CORRESPONDENCE
Shana Stites, University of Pennsylvania, 3615 Chestnut Street, Philadelphia, PA 19104; Stites@UPenn.edu
