When is APOE Test actually useful?

APOE testing is clinically useful for diagnosing familial dysbetalipoproteinemia (type III hyperlipoproteinemia), where genotyping guides treatment. It may also provide risk information in early-onset Alzheimer's families, but routine screening in asymptomatic individuals is not recommended by major guidelines (e.g., American Academy of Neurology). The association between APOE ε4 and Alzheimer's is human-strong, but the test is not deterministic. Without a clear medical indication, the psychological impact of knowing one's risk can be significant. Therefore, APOE testing is only useful in specific clinical scenarios with proper counseling.