The property of immunological testing that allows focus on a certain antibody and antigen without cross reaction is called .

The property of immunological testing that allows focus on a certain antibody and antigen without cross-reaction is called specificity. Specificity refers to the ability of an antibody to bind to a single epitope or a closely related set of epitopes on an antigen, effectively distinguishing it from other similar antigens. This characteristic is crucial in immunological assays such as ELISA (Enzyme-Linked Immunosorbent Assay) or Western blotting, where the goal is to accurately detect and quantify the presence of specific antibodies or antigens in a sample.

High specificity is essential in clinical diagnostics to avoid false positives, ensuring that the test results are both accurate and reliable. If a test has low specificity, it may yield cross-reactive results, which can lead to misinterpretation of a patient's condition or the presence of a disease. Thus, understanding and achieving high specificity in immunological testing is vital for effective disease diagnosis and monitoring.