APOLIPOPROTEIN-E - AN IMPORTANT GENE AND PROTEIN TO FOLLOW IN LABORATORY MEDICINE

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.