What property makes a monoclonal antibody useful in detecting the presence of an anabolic steroid in urine?

The most important property of monoclonal antibodies for use in diagnostics and testing is their **specificity**. An antibody has a unique, three-dimensional binding site that is complementary in shape to a specific part of a molecule, called an antigen. In this case, the monoclonal antibodies are designed to have a binding site that is complementary only to the anabolic steroid molecule. This means they will bind to the steroid and nothing else in the urine. This high specificity prevents the test from reacting to other hormones or chemicals, ensuring an accurate result and avoiding false positives.