APOE and early-onset autosomal dominant Alzheimer disease: Of note, the ACMG has recommended that clinicians not order APOE testing for the purpose of predictive testing for Alzheimer's disease, as heterozygous or homozygous e4 alleles are neither necessary nor sufficient to cause Alzheimer's disease (https://www.acmg.net/docs/ACMG_ChoosingWisely_Final.pdf).