This testing method is a type of immunoassay. It is based on the principle that antibodies will bind to very specific antigens to form antigen-antibody complexes, and enzyme-linked antigens or antibodies can be used to detect and measure these complexes.

To detect or measure an antibody in a person’s blood, a known antigen is attached to a solid surface. A solution containing the patient sample is added. If the patient’s sample contains antibody, it will bind to the antigen. A second antibody (against human antibodies) that is labeled with an enzyme is then added. If the enzyme-linked antibody binds to human antibodies, the enzyme will create a detectable change that indicates the presence and amount of the antibody in the patient sample.

Sources
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(© 1994-2006). Introduction to Antibodies – Enzyme-Linked Immunosorbent Assay (ELISA) [35 paragraphs]. Millipore Corporation [On-line information]. Available FTP: http://www.chemicon.com/resource/ANT101/a2C.asp

S2
(2001). Gerostamoulos, J. et. al. (2001). The Use Of Elisa (Enzyme-Linked Immunosorbent Assay) Screening In Postmortem Blood [5 paragraphs]. TIAFT, The International Association of Forensic Toxicologists [On-line information]. Available FTP: http://www.tiaft.org/tiaft2001/lectures/l13_gerostamoulos.doc

S3
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Harris, N. and Winter, W.