What do studies say about APOE Test?

The APOE genetic test analyzes the ε2, ε3, and ε4 variants of the apolipoprotein E gene. The ε4 allele is the strongest known genetic risk factor for late-onset Alzheimer's disease (LOAD). Studies indicate that carrying one ε4 allele increases risk about 3- to 4-fold, and two ε4 alleles increase risk 10- to 15-fold. However, the test is not diagnostic: many ε4 carriers never develop Alzheimer's, and the disease occurs without ε4. Clinical utility in healthy individuals is debated because no proven prevention strategies exist. Medical guidelines (e.g., Alzheimer's Association) recommend testing only in symptomatic individuals or within research. Potential harms include psychological distress and insurance discrimination. Therefore, testing should only follow genetic counseling. Evidence: strong association but limited predictive value for asymptomatic individuals.