The human apolipoprotein (apo) E gene is polymorphic, with three commo
n alleles (epsilon 2, epsilon 3, epsilon 4) coding for three isoforms
(E2, E3, E4). The isoforms differ from each other by a single amino ac
id substitution, and also differ in their binding affinity for the fou
r apo E receptors. Apo E polymorphism is an important determinant of r
isk for the development of cardiovascular and Alzheimer diseases, the
prevalence of the epsilon 4 allele being increased in both kinds of pa
tients compared with control subjects, Furthermore, the prevalence of
the epsilon 4 allele differs among populations (range 5-40%, respectiv
ely, for Taiwanese and Papua New Guineans), Genotyping or phenotyping
needs to be introduced in clinical laboratories. The choice of the met
hod should be based on the types of patients who are examined. The apo
E genotype is also a determinant of apo E plasma concentration. Stand
ardization of apo E measurement is an important prerequisite before in
vestigating the clinical interest of plasma apo E concentration. Deter
mination of apo E genotype/phenotype and later the plasma concentratio
n are expected to yield useful clinical laboratory information.