Biological or Clinical Significance:
High density lipoprotein (HDL) plays an important role in reverse cholesterol transport, a process by which excess cholesterol from peripheral tissues is returned to the liver for use or excretion. There is a strong inverse correlation between plasma HDL cholesterol concentration and the incidence of atherosclerosis. Lecithin-cholesterol acyltransferase (LCAT) performs a central role in HDL metabolism by catalyzing the formation of cholesteryl esters on HDL through the transfer of fatty acids from the sn-2 positions of phosphatidylcholine (PC) to cholesterol. Two classes of genetic deficiencies are known: familial LCAT deficiency (FLD) and fish-eye disease (FED). FLD is caused by either null or missense mutations; in Class 1 defects, null mutations cause total loss of catalytic activity and virtual absence of LCAT mass, whereas in Class 2, missense mutations are characterized by loss of activity and either normal, reduced, or absent LCAT mass. FED is caused by missense mutations only; these mutations affect either LDL or HDL activity in Class 3 defects, and LCAT mass is reduced. In Class 4 defects, the missense mutations are associated with partial loss of activity against HDL only, and reduced LCAT mass. Direct measurement of the enzyme mass and activity may contribute to the differentiation of LCAT defects.
Principle of Test Method:
The LCAT mass assay is an enzyme-linked immunoassay (ELISA) designed to quantitate LCAT mass in human serum and plasma.
* EDTA is recommended. If serum is used, due to lack of freeze thaw stabiltiy, two aliquots should be submitted to allow for repeat analysis (as needed), Refrigerated and frozen LTS in serum is TBD.