ELISA is the name of one of the tests used for testing for HIV infection (a similar process is also used for other diseases) but the kit for HIV is used only for that particular test. Other kits use the same process -- Enzyme linked Immuno-Sorbent Assay for other types of immunological tests. The older ELISA tests were chromogenic (depending upon colour change to indicate reactivity) but the newer ones are fluormetric and depend upon changes in the florescence pattern. Enhanced Chemluminesence Using Autoanaylzer Vitros, is a automatic machine for carrying out tests and can handle a large batch of samples in sequence and also in the same run do many types of tests. So one is a type of test and the other is a machine for carrying out tests. Most hospitals depend on one or the other form of the ELISA test for their first line tests.