Chemiluminescent immunoassay CLIA

In the most common method for chemiluminescent immunoassay (CLIA), after the immunological reaction and any necessary separation steps, the labeled compounds or complexes react with an oxidizer, eg, hydrogen peroxide, and an enzyme, eg, peroxidase, or a chelating agent such as hemin or metal... 

Fig. 4. Principle of chemiluminescent immunoassay (CLIA) of vitellogenin (Vg). Polyclonal antibodies raised against two distinct classes of Vg-derived yolk proteins (anti-/3 -component and anti-lipovitellin), which are derived from different parts of the same parent Vg molecule, can be utilized to develop a simultaneous one-step CLIA (right side of the figure). Alternatively, a single anti-Vg antibody can be used in a two-step CLIA (left side of the figure). Advantages of each type of CLIA are discussed in detail in section VI.2. IgG, immunoglobulin G.

Enzyme activities may also be measured in urine, cerebrospinal fluid, bone marrow cells or fluid, amniotic cells or fluid, red blood cells, leukocytes, and tissue cells. Cytochemical localization is possible in leukocytes and biopsy specimens (e.g., from liver and muscle). Under ideal conditions, both the concentration of the enzyme and its activity would be measured. Radioimmunoassay (RIA) and its alternative modes such as fluorescence immunoassay (FIA), fluorescence polarization immunoassay (FPIA), and chemiluminescence immunoassay (CLIA) (discussed later), can be used to measure enzyme concentration as well as other clinically important parameters. 

The ELISA and EIA receptor systems measure substances at concentrations as low as a few nanograms (10 g). This sensitivity is not sufficient for detecting many substances and alternate methods have been devised. One is chemiluminescence immunoassay (CLIA), which can measure concentrations in femtogram (10 g) quantities. CLIA depends on the detection of emitted light associated with the dissipation of energy from a substance... 

Chemiluminescence represents emitted light as a result of a certain chemical reaction. Some examples of chemiluminescent reagents are shown in Figure 2. Luminol, acridinium esters, and dioxetanes are the most frequently used labels for chemiluminescence immunoassays (CLIAs). 

ABEI, N-(4-aminobutyl)-N-ethyl isoluminol CLIA, chemiluminescence immunoassay SPE, solid-phase extraction MSPD, matrix solid-phase dispersion RP, reversed phase. 

Immunosensors have been designed which use both direct and indirect immunoassay technology to detect specific analytes within a minute or less in a variety of matrices (see Fig. 9). Indirect immunosensors may employ ELA, FLA, or CLIA principles whereby enzyme-, fluorophore- or chemiluminescent-labeled analyte competes with the target (nonlabeled) analyte for binding sites on the immobilized antibody. Unbound (free) labeled analyte is then quantitated using an electrochemical, optical, or electromechanical transducer and compared to the amount of target analyte in the sample. 

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