The outbreak of the COVID-19 epidemic in 2020 brought unprecedented attention to the in vitro diagnostics (IVD) industry.

At present, there are two main types of detection products for COVID-19 used internationally, which are molecular diagnosis (nucleic acid detection) and immunodiagnosis (antigen and antibody detection). Judging from the diagnostic reagents that have been approved for marketing by the WHO and national drug regulatory authorities, nucleic acid testing products account for the majority, while the number of approved immunologic testing products increased recently.

IVD ( refers to products and services that obtain clinical diagnostic information by testing human samples (blood, body fluids, tissues, etc.) outside the human body to determine diseases or body functions. Currently, its clinical utilization is extremely high that about 80% of the disease diagnosis relies on it to complete. According to the different technologies used in clinical medical test items, IVD products can be divided into immunodiagnosis, biochemical diagnosis, molecular diagnosis, microbiological diagnosis, coagulation diagnosis, tissue diagnosis, blood and body fluid diagnosis, etc.

Core raw materials of IVD diagnostic reagents

Antigens and antibodies are one of the most important in vitro diagnostic materials, which are widely used in enzyme-linked immunoassay, chemiluminescence immunoassay, colloidal gold lateral chromatography, fluorescence immunological lateral chromatography, etc. International advanced companies in antigen and antibody include Hytest, Medix, and Meridian.

Enzyme/coenzyme/enzyme substrates are widely used in almost all IVD sub-fields such as biochemistry, immunity, molecules, POCT, coagulation, blood sugar, and are the most widely used core biological materials.

Magnetic microspheres/microspheres/NC membranes are key materials and reaction carriers for magnetic particle chemiluminescence, latex immunoturbidity, immunofluorescence, liquid phase chips, nucleic acid extraction, and other processes.

Reagent raw materials are the foundation of IVD technology innovation, of which the performance greatly affects in vitro diagnostic systems, and has important strategic significance in the entire industry chain.

The quality of IVD core raw materials is an essential factor that determines the quality of IVD reagents, the basis for the IVD development and innovation, and the most important strategic node in the upstream of the IVD industry. Appropriate raw materials such as antigens are highly compatible with antibodies in clinical samples, which contribute to the detection of antibodies more efficiently. Choosing appropriate raw materials to provide the correct epitope can increase the upper limit of reagent quality, shorten the development cycle, and get twice the result with half the effort.

Immunogenicity and immunoreactivity are two fundamental properties of antigens, which are connected by epitope.

* Immunogenicity: antigen induces the body to produce an immune response, which causes B lymphocytes to produce specific antibodies.
* Immunoreactivity: the ability of an antigen to specifically bind to the antibodies or sensitized lymphocytes it induces.

Selection of antigen as IVD reagents
The choice between natural antigen and recombinant antigen should be determined by the expected downstream applications. If immunodiagnostic tests are developed, natural antigens are more suitable, because natural antigens have similar properties to the same antigens in clinical samples, and have high adaptability to antibodies, making it more likely to detect target antibodies.

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