Is direct binding elisa the same as indirect elisa?

Question

Is direct binding elisa the same as indirect elisa?

Answer 1

No.  That's why they have different names.  ;-)

A direct binding process means that you are using a tag molecule that binds directly to whatever your object of interest is.  In ELISA (Enzyme-Linked ImmunoSorbent Assay), you are using an antibody to bind to an antigen.  Antibodies are Y-shaped molecules with sensitive sites at the tips of their arms that are designed to grab onto a particular part of a molecule, which is called the "antigen."  You can then wash the plate to get rid of the excess and then use an enzyme to detect the remaining antibodies that are latched onto those antigens.  The last step will be to rewash, add a substrate for the enzyme and look for changes based on how much activity the enzyme creates.

Alternatively, you can do this indirectly by using one antibody to latch on and then use a secondary antibody that is linked directly to an enzyme through a conjugate process.

Which you use tends to depend on whether you're looking for the antigen or the antibody in your sample, because the test can detect both.  I know this sounds confusing, but it's hard to explain without the jargon.  You can look at the process here:  http://www.biology.arizona.edu/immunolog...

Or, as simply put as possible:  No, it depends on whether there are one or two intervening steps in the process before you look for the quantities of whatever it is you're trying to find.  If there's only one, it's direct.  If there's two, it's indirect.