Incorporating ethnicity into genetic risk assessment for Alzheimer disease: the REVEAL study experience

Abstract

Purpose: To describe how investigators in a multisite randomized clinical trial addressed scientific and ethical issues involved in creating risk models based on genetic testing for African American participants.

Methods: The following informed our decision whether to stratify risk assessment by ethnicity: evaluation of epidemiological data, appraisal of benefits and risks of incorporating ethnicity into calculations, and feasibility of creating ethnicity-specific risk curves. Once the decision was made, risk curves were created based on data from a large, diverse study of first-degree relatives of patients with Alzheimer disease.

Results: Review of epidemiological data suggested notable differences in risk between African Americans and whites and that Apolipoprotein E genotype predicts risk in both groups. Discussions about the benefits and risks of stratified risk assessments reached consensus that estimates based on data from whites should not preclude enrolling African Americans, but population-specific risk curves should be created if feasible. Risk models specific to ethnicity, gender, and Apolipoprotein E genotype were subsequently developed for the randomized clinical trial that oversampled African Americans.

Conclusion: The Risk Evaluation and Education for Alzheimer Disease study provides an instructive example of a process to develop risk assessment protocols that are sensitive to the implications of genetic testing for multiple ethnic groups with differing levels of risk.

Fig. 1

Cumulative risk estimates to age 85 for Alzheimer disease (AD) for first-degree relatives of AD patients based on APOE genotype, gender, and ethnicity. □ White females; African American females; white males; and ■ African American males.

Fig. 2

Sample cumulative risk curves presented to study participants all of whom have a first-degree relative with Alzheimer disease (AD). The risk curves apply to participants who are found to have an APOE ∈3/∈4 genotype. “APOE 34” refers to the participants' individual risk profiles specific to their genotype–gender–ethnicity combinations. “First Degree” is a comparison line that shows the risk for AD among the population of people with the same gender–ethnicity combination as the participant and a first-degree relative with AD. “General Population” is another comparison line that shows the risk for AD within the same ethnic group as the participant regardless of gender or whether a person has an affected first-degree relative. Explanations of each line are provided verbally to study participants.