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Glossary

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:
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.

Recovery:
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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