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J Neural Transm (Vienna). 2019 Jan;126(1):65-85. doi: 10.1007/s00702-018-1934-9. Epub 2018 Oct 31.

Clinical implications of APOE genotyping for late-onset Alzheimer's disease (LOAD) risk estimation: a review of the literature.

Author information

1
Institute of Medical Science, University of Toronto, Toronto, ON, Canada.
2
Pharmacogenetics Research Clinic, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON, M5T1R8, Canada.
3
Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
4
Faculty of Medicine, Queen's University, Kingston, ON, Canada.
5
Institute of Medical Science, University of Toronto, Toronto, ON, Canada. daniel.mueller@camh.ca.
6
Pharmacogenetics Research Clinic, Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON, M5T1R8, Canada. daniel.mueller@camh.ca.
7
Department of Psychiatry, University of Toronto, Toronto, ON, Canada. daniel.mueller@camh.ca.

Abstract

Alzheimer's disease is a genetically complex neurodegenerative disorder representing the leading cause of dementia. Advances in personal genomics are increasing the public uptake of genetic susceptibility testing for complex diseases such as late-onset Alzheimer's disease (LOAD). For LOAD, the discovery of the major risk ε4 allele of the APOE gene has prompted a debate on the ethics and utility of presymptomatic (i.e., predictive) testing. Although the mechanistic contribution of APOE to disease onset remains uncertain, presymptomatic genetic testing provides a relative risk of developing LOAD. Presymptomatic testing for complex disorders, such as LOAD is much less conclusive than early-onset Alzheimer's disease (EOAD) which follows a Mendelian inheritance pattern. Given the lack of preventive strategies available for EOAD or LOAD, APOE genotyping offers limited clinical utility, thus, raising ethical and practical questions. We conducted a systematic search of five electronic databases or primary studies published during January 2008-January 2018 which investigated practical and ethical issues of presymptomatic APOE genotyping for LOAD risk estimation. We identified 31 articles which suggested that APOE genotyping for LOAD susceptibility provides potential benefits to at-risk patients and can guide changes in positive health-related behaviors. However, other individuals may experience test-related anxiety, depression and psychological distress. Future research should focus on developing an integrated risk assessment tool to enhance the utility of APOE genotyping. Furthermore, empirical research is required to understand actual psychological and social implications associated with testing.

KEYWORDS:

APOE; Alzheimer’s disease; Direct-to-consumer; Ethics; Genetic testing

PMID:
30382407
DOI:
10.1007/s00702-018-1934-9

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