What is Chemiluminescence Immunoassay (CLIA)?
Introduced in 1977, Chemiluminescence Immunoassay (CLIA) revolutionized immunoassay techniques by combining chemiluminescence with the immune response. By building on radioimmunoassay principles, CLIA offers several advantages, including high sensitivity, strong specificity, and a broad detection range. Best of all, it’s easy to use and doesn’t require expensive equipment.
How CLIA Works
CLIA relies on two systems: the immunoassay system and the chemiluminescence system. First, in the immunoassay system, chemiluminescent substances or enzymes are used to label the antigen or antibody. When these react, they form an immune complex. After that, the chemiluminescence system activates when you add a luminescent substrate and an oxidant. The oxidant excites the chemiluminescent substance, causing it to emit light (photons). The intensity of the light is measured by a detector and corresponds to the analyte concentration.
Because of its efficiency, CLIA is widely used in diagnostic testing across various fields.
Types of Chemiluminescence Immunoassays
CLIA comes in three types based on the markers used:
- Chemiluminescence Immunoassay (CLIA): In this type, chemiluminescent agents such as luminol or acridinium esters label the antibodies or antigens.
- Luminol-labeled CLIA: Luminol emits light through an oxidation reaction, typically using H₂O₂ as the oxidant. Catalysts like HRP or metal ions speed up the process. Additionally, adding boosters can increase luminescence up to 1000 times, making it ideal for protein and nucleic acid detection.
- Acridinium Ester-labeled CLIA: Acridinium esters react quickly with H₂O₂ and produce high quantum yield. Since they don’t need a catalyst, this simplifies the process while providing high sensitivity and low background noise.
- Chemiluminescent Enzyme Immunoassay (CLEIA): In CLEIA, enzymes such as HRP and ALP act on luminescent substrates to produce light. Newer substrates like CSPD and CDP-Star improve the speed and sensitivity of these reactions, making them ideal for DNA and gene detection.
- Electrochemiluminescence Immunoassay (ECLIA): ECLIA uses an electrochemical reaction to trigger light emission. It typically uses compounds like ruthenium terpyridine and tripropylamine, which create stable and continuous light. Thanks to its high sensitivity and full automation, ECLIA delivers quick and reliable results.
Why ECLIA Stands Out:
- Provides long-lasting luminescence with high sensitivity
- Uses stable markers and supports multi-labeling
- Offers a wide detection range with strong linearity
- Delivers fast results in just 18 minutes
- Supports multiplex detection and repeatable measurements
Applications of CLIA and CLEIA
CLIA and CLEIA are commonly used to detect various biological molecules, such as tumor markers, cardiac markers, thyroid function, insulin, C-peptide, and markers for infectious diseases. These assays are particularly valuable for therapeutic drug monitoring, hormone analysis, and cytokine detection.
Instruments used for these assays are available as fully automatic or semi-automatic systems. Most fully automatic systems use magnetic bead separation or plastic orifice plate systems.
Why CLIA is the Top Choice
CLIA offers exceptional sensitivity, allowing for the detection of even trace amounts of analytes. It also provides a broad dynamic range, ensuring a linear relationship between light intensity and analyte concentration. Furthermore, the use of enhancers extends the reaction time, which maintains steady and strong light emission.
Due to its precision, speed, and scalability, CLIA remains a leading method for clinical diagnostics and research. Whether in the medical lab or research setting, CLIA consistently delivers fast, accurate, and reliable results.
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Ref:
Cinquanta L, Fontana DE, Bizzaro N. Chemiluminescent immunoassay technology: what does it change in autoantibody detection? Auto Immun Highlights. 2017 Dec;8(1):9.
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AF546, Alexa Fuor 488 conjugation, AF532, Cy3b maleimide, 6 fam phosphoramidite, etc