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These terms are commonly used in Immunoassay technology.

Antibody: A molecule, produced in respons to an antigen, that has the particular property of binding specifically with the antigen that has induced its formation.

Antigen: A molecule that, upon introduction into the body is recognized by the cellular or humoral part of the host’s immune system.

Autoantibody is an antibody produced by the immune system that is directed against one or more of the individual’s own protein. These autoantibodies can sometimes disturb the ELISA test.

Calibrator: Another word for standard.

CV: Coefficient of Variation. The CV is a statistical expression of the precision of an assay based on the average and standard deviation of multiple measurements.

Competitive assay: The analyte competes with a predetermined fixed amount of labelled analyte for the binding sites of an antibody in a solution. A second antibody, coupled to the plate, directed against the first antibody separates the antigen-antibody complex.

Conjugate: A molecule labeled with a specific enzyme to be detectable by a specific method.

Detection limit: Reflects the minimum level that is clearly distinguishable from Calibrator 0. Concentrations of samples with absorbance below Calibrator 1 should not be calculated, but rather expressed as less or equal to the concentration of calibrator 1.

ELISA: Enzyme-Linked Immunosorbent Assay.

Epitope: The smallest structural area on an antigen that can be recognized by, and bind to an antibody.

Hook dose effect:
The antigen-saturated detection antibodies in solution can be washed off giving a falsely low signal. A ”hook” is observed in the curve when data is plotted as a signal versus antigen concentration.

IVD: In Vitro Diagnostic.

Lot number: Number that identifies the specific production batch of the ELISA.

Matrix effect: An interference caused by a constituent of the sample itself. This usually relates to the pH, osmolarity or composition of the sample. If the sample characteristics exceed the limitations tolerated by the assay, a matrix effect will result and sample detection becomes non-linear.

Monoclonal antibody: An antibody derived by one type of immune cell that is a clone of a single parent cell. It is directed against one epitope on the antigen molecule.

Precision: A statistical evaluation of the ability to detect the same value over multiple measurements. Precision can be divided into intra-assay and inter-assay. Intra-assay precision reflects the statistical repeatability within a single assay while inter-assay precision reflects repeatability over a number of different assay runs.

Polyclonal antibody:
Population of antibodies directed against a specific antigen, each recognizing different epitopes on the antigen molecule.

A test done by diluting a sample and with the addition of sample to ensure that there does not exist any conflicts between the sample and the test. The statistical value should be around 100%.

Simultaneous assay:
The sample and detection antibody is added simultaneously durring the assay procedure.

Sequence assay:
The sample and detection antibody is added in steps durring the assay procedure.

Specificity: The degree of selectively binding the analyt of interest without disturbances by cross-reaction or interfering substances.

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