The RIA test system was used extensively before the invention of the ELISA test system. However, in the late '60s and early '70s, there were some difficulties getting an RIA test. During this time, most individual researchers used self-made methods to carry out RIA tests. This is not because the home cooking method is (actually not) more effective.
The reason is that (for financial and technical reasons) they cannot match the capabilities and facilities of commercial manufacturers such as Abbott and Organon Teknika. These companies also paid attention to this phenomenon and later invented the ELISA testing system.
As already mentioned, the ELISA test system was discovered during the same period. Compared to RIA, ELISA is much cheaper, less technically recommended and, because it is not irradiated, much safer than RIA. There are many companies like Bosterbio that provide ELISA service via https://www.bosterbio.com/services/assay-services/elisa-testing-service.
However, complicated preparation and procedural steps have prevented the spread of this new testing system. If someone can make an ELISA kit, they will provide the essential materials to use for the test and ready to use. The difficulties will be overcome. This production had the same idea and started with the commercialization of the ELISA kit, which contains essential components for the ELISA test, which can significantly reduce the difficulty of preparation and procedure.
An important step in the development of an ELISA kit is the use of the solid phase technique. Using solid-state techniques, scientists cannot bind antigens or antibodies covalently within the microtiter holes. In addition, the invention of automated machines such as microtiter plate readers and washing instruments boosted the ELISA kit population.