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Thread: Elisa

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    Default Elisa

    ELISA

    An HIV ELISA, sometimes called an HIV enzyme immunoassay (EIA) is the first and most basic test to determine if an individual is positive for a selected pathogen, such as HIV. The test is performed in a 8 cm x 12 cm plastic plate which contains an 8 x 12 matrix of 96 wells, each of which are about 1 cm high and 0.7 cm in diameter.

    The ELISA Method
    Partially purified, inactivated HIV antigens pre-coated onto an ELISA plate
    Patient serum which contains antibodies. If the patient is HIV+, then this serum will contain antibodies to HIV, and those antibodies will bind to the HIV antigens on the plate.
    Anti-human immunoglobulin coupled to an enzyme. This is the second antibody, and it binds to human antibodies.
    Chromogen or substrate which changes color when cleaved by the enzyme attached to the second antibody.

    False positives

    It is entirely possible that an individual not infected with HIV has antibodies which may give a positive result in the HIV ELISA. This is called a false positive. One reason for this is that people (especially women who have had multiple pregnancies) may possess antibodies directed against human leukocyte antigens (HLA) which are present on the host cells used to propagate HIV. As HIV buds from the surface of the host cell, it incorporates some of the host cell HLA into its envelope. False negatives can occur during the window between infection and an antibody response to the virus (seroconversion).

    ELISA data from three patients

    Positive Control Negative Control
    1.689 0.153
    Patient A Patient B Patient C Assay Control
    O.055 0.412 1.999 0.123

    Above is ELISA data from three patients. Numbers are expressed as optical density at 450 nm. The cutoff value indicating a positive result is 0.500. Optical densities of 0.300 to 0.499 are indeterminate and need to be retested. Values below 0.300 are considered to be negative. In most cases, a patient will be retested if the serum gives a positive result. If the ELISA retests are positive, the patient will then be retested by western blotting analysis.

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    My post was ELISA!!!!

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