ELISA, the most commonly performed diagnostic test in developing countries like India, to detect HIV Antibodies (Ab) is classified on the basis of Antigens (Ag) used.
1st Generation - used infected viral cell lysate as antigen.
2nd Generation - used glycopeptides (recombinant antigens)
3rd Generation - synthetic peptides are used as antigens.
4th Generation, are the newer tests for simultaneous detection of p24 Ag (HIV-1 Ag) and HIV-1/HIV-2Ab.
HIV tests utilizing Recombinant antigens would be 2nd Generation.
Abbot AxSYM test is a 3rd Generation test.