Asha M. Jagtap.
Rajarambapu college of
pharmacy , kasegaon .
An immunoassay is a biochemical test that
measures the presence or concentration of
a macromolecule or a small molecule in a solution
through the use of an antibody (usually) or
an antigen (sometimes).
The molecule detected by the immunoassay is
often referred to as an "analyte" and is in many
cases a protein.
1.RIA (RADIO IMMUNO ASSAY)
It was developed by “Rosalyan Yalow and S.
A. Berson in the 1950s”.
Development of the ‘RIA for insulin;
It is a scientific method used to
test antigens without the need to use a
It involve competition between
labelled and unlabelled antigen for binding with
specific antibodies so antigen-antibody
complex is formed .& radio activity is measured.
It is an alternative technique employed in
diagnosis of several antigen like hepatitis.
It is competitive binding assay in which serum
sample is combined with radioactively labelled
antigen and antibodies to the antigen .
The radioactive antigen and antigen specimen
will compete for antibody .the antigen-antibody
complex thus formed is isolated and analyzed for its
radioactivity. The concentrations ‘standard dose
1. Detection of insulin.
2. Detection of narcotic drug .(morphine and
3. Detection of digoxin .
4. Determination hydromorphon and
hydrocondron in human serum .
5. Measurement of ferritin.
6. Thyroid testing .
2.ELISA (ENZYME LINKED IMMUNOSORBENT ASSAYS)
The ELISA is a fundamental tool of clinical
immunology and is used as an initial screen for
Enzyme-linked ImmunoSorbent Assay ,also
called ELISA ,enzyme Immuno Assay or ELA is
a biochemical technique used mainly in
immunology to detect the presence of an
antibody or an antigen in a sample.
Antigen –antibody interaction this test
allows for easy visualization of results and can
be completed without the additional concern of
radioactive material used.
In which enzyme like alkaline phosphate
is employed to visualize antigen-antibody
TWO TYPE –
1. Direct ELISA ( double antibody sandwich)
2. Indirect ELISA ( direct antigen coating )
1. DIRECT ELISA
It is performed in microtitre
well, in which antibody to specific antigen is
adsorbed to well, on which specimen
containing antigen to be demonstrated is
added. Unbound antigen are washed off and
enzyme –linked antibody specific for test
antigen is added which binds to complexed
antigen forming sandwich.
2. INDIRECT ELISA -
It is also performed in microtitre well, in
which antigen to the antibodies demonstrated is
adsorbed to well ,on to which patient antiserum
specimen is added If serum contains specific
antibody ,it will bind to the adsorbed antigen
.un-reacted serum is washed off and enzyme –
linked anti-HSIG is added, which will bind to
antibodies in the initially formed antigen
1. It is a useful tool for determination serum
antibody concentrations.( such as with the HIV
2. For detecting the presence of antigen .it has
also found applications in the food industry in
detecting potential food allergens such as milk
3. ELISA can also be used in toxicology as a rapid
presumptive screen for certain classes of drug .
4. Diagnosis of infection .