What is the difference between 3rd and 4th Generation ELISA ??

Hello all,
As title says, I just wanted to know what is the difference between 3rd and 4th generation ELISA ??
my understanding is that:
3rd generation = antibody test
4th generation = antibody + antigen
am i correct ??
Thanks

[Vance2335]

Yes I believe that is correct.

[avonelle38]

Yes. The 3rd generation tests for antibodies only while the 4th generation tests for both antibodies and particles of the virus itself.

[Teak]

Antigen tests do not identify HIV virus particles. It is important to realize that the p24 antigen test detects soluble p24 antigen, presumably following viral replication, and does not specifically identify live virus. Therefore, a positive antigen test does not confirm that a sample is infectious, and should not be used for that purpose. The only means available to demonstrate that a sample contains infectious virus is by virus isolation and culture. A negative result for antigen does not rule out infection, because the test lacks exquisite sensitivity; i.e., the test should not be used to verify noninfection. Antigen detection signals infection, however, and positive results in seronegative individuals can be an effective, although not cost effective, means to identify early infection.

[crossfire123]

thanks guys