The immunoassay is a laboratory diagnostic test using an immunological reaction of antibodies. It measures the formation of antibody-antigen complexes in blood samples or other body fluids and it is used when an analyte needs to be detected in a qualitative (positive or negative) or quantitative (amount measurement) manner. The analyte can either be some natural part of the body (e.g. hormones), may be produced by the body under specific conditions (e.g. cancer antigen), or of those that naturally do not occur (e.g. a Hepatitis B antigen). Immunoassays generally use a method that produces an amplified signal that can then be visualized by using an analyzer or another detection method.