Sandwich immunoassays interference

Another useful heterogeneous EIA is the double antibody or "sandwich" immunoassay. In a sandwich immunoassay, an untagged antibody or capture antibody is the first reagent bound to the solid phase. The test sample and then the enzyme labeled antibody are added sequentially. The unbound components are removed by washing after each incubation. Enzyme-labeled antibody is detected by addition of a substrate as above. The capture antibody is particularly useful when the test sample consists of a complex mixture of materials. The capture antibody "fishes-out" the target antigen and other components of the test sample (which could interfere with subsequent steps in the immunoassay) are more effectively washed away. 

Rl. Ruan, K.-H., Hashida, S., Yoshitake, S., Ishikawa, E., Wakisaka, O., Yamamoto, Y., Ichioka, T., and Nakajima, K., A more sensitive and less time-consuming sandwich enzyme immunoassay for insulin in human serum with less serum interference. Ann. Clin. BiochertL 23, 54—58 (1986). 

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