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==Introduction==
==Introduction==
[[Image:ELISA.jpg|thumb|right|150px|Double Antibody Sandwich ELISA]]
[[Image:ELISA.jpg|thumb|right|150px|Double Antibody Sandwich ELISA]]
The Enzyme Linked Immunosorbent Assay (ELISA) is an immunoassay commonly used to detect the presence of an antigen or antibody in a sample. It is a powerful tool in clinical immunology and can be used to determine whether an individual is positive for a specified pathogen, so is often the first test used in disease diagnosis. Utilizing the principle of antigen-antibody interaction, the test allows easy visualisation of results and, since its introduction in 1971, has quickly replaced radioimmunoassays for diagnostic purposes.
The Enzyme Linked Immunosorbent Assay (ELISA) is an immunoassay commonly used to detect the presence of an antigen or antibody in a sample. It is a powerful tool in clinical immunology and can be used to determine whether an individual has been exposed to a specified pathogen. Utilizing the principle of antigen-antibody interaction, the test allows easy visualisation of results and, since its introduction in 1971, has quickly replaced radioimmunoassays for diagnostic purposes.
*There are two basic types of ELISA:
*There are two basic types of ELISA:
==Applications==
==Applications==
*Detection and indentification of disease agents, e.g. type and subtype
*Detection and indentification of disease agents, e.g. type and subtype
*Identification of specific antibodies, e.g. used in serodiagnosis for epidemiological studies
*Identification of specific antibodies, e.g. used in serodiagnosis for epidemiological studies
*Quanitification of specific antibody isotypes, e.g. IgM/IgG ratio
*Quanitification of specific antibody isotypes, e.g. IgM/IgG ratio
'''Competitive VS Non-competitive'''
'''Competitive VS Non-competitive'''
*As their name implies, competitive assays measure the competition between a pre-titrated (fixed amount) of labelled antigen and unknown quantity of sample antigen in their affinity to an antibody. The process can be reversed to measure the competition between labelled and unlabelled antibody.
*As their name implies, competitive assays measure the competition between a pre-titrated (fixed amount) of labelled antigen and an unknown quantity of sample antigen in their affinity to an antibody. The process can be reversed to measure the competition between labelled and unlabelled antibody.
*Competitive techniques:
*Competitive techniques:
**Easier to quantify
**Easier to quantify