Immunoassay involves diverse techniques that utilize the reaction of antigens binding to specific antibodies. This interaction results in a quantifiable signal that is related to the concentration of a definite analyst in the solution. In 1959, Yalow and Berson developed the immunoassay technique which has, over the time, enhance the scope of diagnosis and research in the field of medicine. Now, many assays have been developed, which can be automated easily to be used as ideal methods for testing sensitive, high throughput and specific paradigms.
Immunoassays are now standard procedures to initially test the urine in drug testing programs. These drug testing programs have pre-defined drugs and metabolites which are easily identified by the immunoassay technique. These tests identify one or more drugs which are present within the same class of compounds because of which they can easily screen and detect the negative specimens. Further confirmatory tests are done on the specimens which are designated as ‘non negative/ presumptive positive’. Specimens that are proved to be positive have been reported as ‘positive’ in both the immunoassay and the confirmatory tests.
This chapter describes the core principles on which immunoassay systems function. Moreover, they’ll also tell in detail about the analytical aspects of immunoassays which the laboratories have to fulfill while entertaining the drug-testing programs. Limitations and some analytical issues pertaining to immunoassays are also discussed in this chapter.