The treatment may prove most useful for people who strongly suspect they have been recently infected. Standard ELISA/EIA tests, the ones most frequently used for preliminary HIV testing, cannot always immediately detect the presence of HIV antibodies in HIV-infected individuals. This is why a more complex and expensive test, the Western Blot, is usually administered (barring any other post-ELISA/EIA potential HIV transmission), three months following a negative ELISA/EIA result. There are newer tests, a group called the nucleic acid based tests (NATs), which can conclusively detect seroconversion within 12 days of infection. These tests are much more expensive and complex than the ELISA/EIA/Western Blot series, but may become the standard of testing if OPAL therapy proves successful in humans.