According to Tijssen in "Practice and Theory of Enzyme Immunoessays," EIA stands for enzyme immunoassay test. Tijssen explained that an EIA tests for enzymatic activity by instigating a controlled immune response. Accordingly, Winn and Koneman indicate that EIAs can test for HIV in "Color Atlas and Textbook for Diagnostic Microbiology" by combining immunoglobulin G with an enzyme---usually alkaline phosphatase---then adding a color reactant to measure HIV antibody content.
Purpose of EIA
According to the Office of Technology Assessment of U.S. Congress in "Medical Testing and Health Insurance," EIA tests are useful to screen for HIV in high-risk patients. Yolanda Tayler concurs in "Battling HIV/AIDS," stating that laboratories with high specimen volumes should use EIA tests as a screener, then Western blot tests for confirmation.
In "Porth Pathophysiology," Hannon, Pooler and Porth explain that EIA results require confirmation due to frequent inaccurately positive results. The authors detailed the following causes for falsely positive results: viral DNA infections, primary biliary cirrhosis, antibodies of class II leukocytes, Stevens-Johnson syndrome, autoimmune disorders, chronic renal failure and hematologic malignant disorders, among others.
Immunoglobulin G
In "Immunology for Life Scientists," Lesley-Jane Eales defined immunoglobulin G as the primary antibody released during a secondary immune response. Moreover, Eales states that immunoglobulin G, or IgG, is the only antitoxic antibody in the human body. Correspondingly, immunoglobulin G is a critical element in the body's response to an HIV infection. Alternately, due to immunoglobulin's typical involvement in many infections, the EIA test's concentration on the enzyme contributes to its inaccuracy.
Western Blot Test
Contemporary medicine considers the Western blot test more accurate than the EIA and thus, effective to measure its accuracy, as stated in "Porth Pathophysiology." Similar to the EIA, a Western blot test begins by arranging HIV antigens in lines by weight via electrophoresis on a sheet of nitrocellulose paper. Laboratory clinicians then add a sample to the antigens. In the event of an infection, antibodies from the sample will bind to a specific line, indicating an infection and the specific HIV strain infecting the owner of the sample. As with an EIA test, the tester adds a color substrate to the lines to identify the presence of antibodies bound to antigens, thus providing results for the test.
References
- "Practice and Theory of Enzyme Immunoessays"; P. Tijssen; 1985
- "Koneman's Color Atlas and Textbook for Diagnostic Microbiology"; Washington C. Winn and Elmer W. Koneman; 2006
- "Medical Testing and Health Insurance"; Office of Technology Assessment of U.S. Congress; 1998
- "Porth Pathophysiology: Concepts of Altered Health States"; Ruth A. Hannon, Charlotte Pooler and Carol Mattson Porth; 2009
- "Immunology for Life Scientists"; Lesley-Jane Eales; 2003
