What is a Diagnostic Immunoassay Test_
                     What is a Diagnostic Immunoassay 
Test?
A diagnostic immunoassay test is a method 
of analysing a sample to determine 
whether it contains a specified substance. 
The analysis can also indicate how much of 
the substance is present.
Some immunoassay tests are relatively simple 
and can be carried out at home (e.g., test 
strips for urinary ketones, blood glucose or 
human chorionic gonadotrophin). 
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What is a Diagnostic Immunoassay Test?
Others are more sophisticated and require 
specialist equipment and trained personnel 
to carry out the analysis (e.g., tests for 
human growth hormone).
Immunoassays are based on the principle 
that if an antibody is placed in contact with 
an antigen that specifically binds to it, then 
the two molecules will form a complex 
which can be identified using a secondary 
antibody and associated detection system. 
A wide range of detection systems exist, 
but all operate by enabling the presence of 
the complex to be observed in some way. 
The simplest methods involve changing 
colour after adding a solution containing 
the labelled secondary antibody; other 
methods include using radioisotopes, 
fluorescence or chemiluminescence. 
Diagnostic immunoassays are in vitro 
diagnostic tests that utilize specific binding 
between an antigen and an antibody. 
The antigen-antibody complexes have 
various physicochemical properties that 
can be measured using different detection 
methods.
Diagnostic immunoassays are widely 
used to detect or measure antigens and 
antibodies in a sample.