Tetramethylbenzidine (TMB) substrate concentration in a plasma/serum immunoassay probe for detecting specific antibodies or antigens

What This Test Measures

TMB is a colorless compound that turns blue or brown when it reacts with enzymes (like horseradish peroxidase) in immunoassays. This reaction indicates the presence and concentration of specific analytes, such as antibodies or antigens, in your plasma or serum. The test uses this chemical reaction to provide a quantitative or qualitative measurement of the target substance.

How the Test Works

In this test, TMB acts as a substrate in an enzyme-linked immunoassay (ELIA) or similar method. When antibodies or antigens bind to the test surface, an enzyme attached to another antibody binds to them, catalyzing the conversion of TMB into a colored product. The intensity of the color correlates with the amount of target substance present, allowing for measurement.

Common Uses

TMB testing is often used in research, diagnostics, and research labs to detect low concentrations of proteins, hormones, or pathogens. It is frequently employed in assays for infectious diseases, autoimmune conditions, or monitoring certain biomarkers in clinical settings.

Preparation for the Test

No special preparation is needed for this test. You may be asked to fast for 8–12 hours before your blood draw if your doctor specifies it, but this is not always the case for TMB-based assays. Bring any medications or supplements you’re currently taking to your appointment.