Plate-based assays designed for detecting and quantifying substances such as peptides, proteins, antibodies and hormones, enzyme-linked immunosorbent assays (ELISAs) are used to detect antibodies related to several infectious conditions. There is a wide range of infectious disease ELISA kits available for the detection of human IgG, IgA and IgM antibodies to bacterial, viral, fungal and protozoal antigens. This common but versatile laboratory technique offers many advantages for physicians and laboratories:
- Offers quick and accurate results
- Highly sensitive
- Simple to perform
- Easily automated
- Compare favorably with other methods such as radioimmune assay (RIA) tests (do not need radioactive substances or a costly radiation counting apparatus)
- Needs just a simple blood sample obtained either from the arm or fingertip of the patient
- ELISA kit can test for antibodies as well as antigens as well
- Convenient and easy-to-use for HIV testing
In August, the FDA approved the use of a polymerase chain reaction (PCR) based test for the diagnosis of the Ebola Zaire virus. Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing and IgM ELISA are among the diagnostic tests for Ebola a few days after the symptoms begin. The test binds anti-human IgM to a bound surface. Serum from the patient is added to the surface and it will bind to the anti-human IgM if it contains IgM to Ebola. When the Ebola antigen is added, it will bind to the anti-Ebola IgM. A substrate is added and the signal produced by enzyme-substrate reaction is studied. A color change would indicate the presence of the Ebola virus. Since this assay uses surface binding for separation, washes are repeated several times between each ELISA step to remove unbound materials.
As with all assays, the consistency and dependability of the ELISA depend upon the use of appropriate techniques and attention to detail.