Direct measurement of low density lipoprotein in whole blood by silver-enhanced gold-labelled immunoassay.

A competitive silver-enhanced gold-labelled immunoassay has been developed for the direct measurement of low density lipoprotein (LDL) in whole blood. Immobilized LDL and sample LDL compete for added antibody. Quantitation of the bound antibody/antigen complex is achieved by the addition of gold-labelled anti-immunoglobulin G followed by enhancement of absorbance by addition of silver ions. Whole-blood samples from fasting patients were assayed directly for LDL by the procedure and the corresponding plasma samples were assayed for total cholesterol, high density lipoprotein and triglycerides followed by the indirect calculation of LDL cholesterol. The correlation between the two methods was good (r = 0.82) and the SEGLISA exhibited good precision.