In vitro diagnostic reagents are widely used in medical research and clinical testing, because of stable quality and reliable effect, it not only provides a basis for scientific research and diagnosis and treatment, but also provides technical information for disease prevention and control.
　　
There are many kinds of in vitro diagnostic reagents, involving many disciplines. Due to the increasing interdisciplinary phenomenon and the endless emergence of new technologies, it is difficult to classify them simply according to a certain principle. From the perspective of clinical specialty, it can be divided into clinical hematology humoral test reagents, clinical chemistry reagents, clinical immunology reagents, and microbiology, cell histology, molecular biology reagents, etc. From the perspective of methodology, it can be divided into chemical chromogenic method, immunoturbidimetry, enzyme-linked immunoassay, colloidal gold method, immunofluorescence method, chemiluminescence reagents, molecular biology reagents, immunohistochemistry reagents, immunocytochemistry reagents, etc.
　　
Clinical biochemical reagents are mainly used for testing with semi-automatic and automatic biochemical analyzers and other instruments. There are a variety of analytical methods and technical principles used in commonly used clinical biochemical reagents, which are described below.
　　
1. spectrum analysis technique
This technique is based on the measurement of the wavelength and intensity of the emitted, absorbed or scattered radiation generated by the transition between the quantized energy levels within the substance when the substance interacts with the radiation energy, so as to analyze it. According to the different objects, spectral analysis techniques can be divided into atomic spectrometry (measurement of ions, trace elements, etc.) and spectrophotometry; according to the different ways of obtaining, the technology can be divided into absorption spectrophotometry and emission spectroscopy.
　　
Absorptiometry is a method of analysis based on the characteristics of selective absorption of light by substances in solution. Colored solution has the characteristics of selective absorption of light, different substances due to their different molecular structure, the absorption capacity of different wavelengths of light is different, each substance has a specific absorption spectrum. When light of a certain wavelength passes through the solution of the substance, the method of determining the content of the substance according to the degree of absorption (absorbance) of the substance is called the absorbance method.
　　
Absorptiometry can be divided into colorimetry and spectrophotometry. Colorimetry can be divided into visual colorimetry and photoelectric colorimetry. The principle of spectrophotometry is similar to that of photoelectric colorimetry, which is a method of analysis by measuring the intensity of solution transmittance through photocells or photocells.
　　
When the use of colorimetric method for the determination of a chemical composition in the solution, usually need to add a chromogenic agent, so that it produces colored compounds, the depth of color and the content of the chemical composition to be measured is proportional to the concentration of the substance to be measured.
　　
Emission spectroscopy is a method of qualitative and quantitative analysis by measuring the wavelength and intensity of the emission spectrum of a substance.
　　
Many substances are photoluminescent, that is, they absorb electromagnetic radiation and then re-emit radiation of the same or longer wavelength. The most common types of photoluminescence are fluorescence and phosphorescence. The method of analysis using fluorescence intensity is called fluorescence method. In fluorescence analysis, the light absorbed when the molecules of the substance to be measured become excited is called excitation light, and the fluorescence generated when the molecules in the excited state return to the ground state is called emission light. The fluorescence method measures the strength of the fluorescence emitted by the molecules of the substance to be measured after being excited by light, rather than measuring the strength of the excitation light. Any compound that can produce fluorescence can be qualitatively or quantitatively measured by fluorescence analysis.
　　
Scattering spectroscopy is a kind of quantitative measurement method to determine the degree of light absorption or light scattering after light passes through solution suspended particles. It is mainly used in immune detection systems, often called immune turbidimetry.
　　
2. electrochemical analysis
The method of analyzing the potential, current or power change of a chemical battery by using the electrochemical properties of a substance is called electrochemical analysis. There are many kinds of electrochemical analysis methods, the analysis method of determining the material content of the original battery electromotive force is called the potential method or the potential analysis method, the analysis method of the material content by the determination of resistance is called the conductivity method, and the mutation of some physical quantity is used as the indication of the end point of titration analysis, called the capacitance analysis method. At present, the electrochemical analysis method used in clinical practice is mainly ion-selective potential analysis, which uses the relationship between electrode potential and active substances in solution to analyze.
　　
From a methodological point of view, clinical immunodiagnostic reagents can be divided into different types such as immunoturbidimetry (introduced in scattering spectroscopy), enzyme-linked immunosorbent assay, and chemiluminescence.
　　
3. ELISA
This technique is an immunolabeling detection technique that combines the specificity of the enzyme-catalyzed reaction with the specificity of the antigen-antibody reaction. The principle is that the enzyme is combined with the antibody or antigen into an enzyme-labeled conjugate. The enzyme-labeled conjugate not only retains the immunological activity of the antigen or antibody, but also retains the catalytic activity of the enzyme on the substrate. After the specific reaction between the enzyme-labeled antibody and the antigen is completed, the corresponding substrate for the enzyme is added, and the color reaction is completed through the enzyme-catalyzed substrate, and the antigen or antibody is located, qualitatively and quantitatively determined.
　　
Immunofluorescence technology This technology is the use of substances to absorb light energy to produce excited state and luminescence characteristics, the characteristics of the fluorescein with chemical methods combined with specific antibodies or antigens, without damaging the antibody or antigen activity of a fluorescent microscope tracing technology.
　　
4. flow cytometry
The technology is a detection means for quantitative analysis and sorting of single cells or other biological particles on the surface and internal components of the membrane. It can analyze tens of thousands of cells at high speed and measure multiple parameters from one cell at the same time. Compared with the traditional fluoroscopy, this method has the characteristics of high speed and high accuracy.
　　
5. Colloidal Gold Technology
The technology can be divided into colloidal gold immune infiltration test and colloidal gold immune chromatography test according to the flow form of the liquid.
　　
6. chemiluminescence immunoassay
This technology is a combination of chemiluminescence assay with high sensitivity and high specificity of the immune response, for a variety of antigens, haptens, antibodies, hormones, enzymes, fatty acids, vitamins and drugs and other detection and analysis technology. Chemiluminescence immunoassay contains two parts: immune reaction system and chemiluminescence analysis system.
　　
Clinical molecular biology diagnostic reagents are commonly referred to as genetic diagnostic reagents, and their technical principles mainly include nucleic acid molecular hybridization technology, DNA sequencing technology, gene chip technology, etc.
　　
Nucleic acid molecular hybridization technology, also known as gene probe technology, is a technology that uses the principle of nucleic acid denaturation, renaturation and complementary base pairing to detect whether a sample contains a nucleotide sequence paired with a known probe sequence. This technology is the earliest and most basic molecular biology technology in clinical application, and is the basis of imprinting hybridization, gene chip and other technologies.
　　
7. DNA sequence analysis
This analytical technique is an important basic technique in molecular biology. Taking the sequencer of ABI company as an example, it uses four fluorescent dyes to label the terminator or primer respectively. After Sanger sequencing reaction, the reaction products have different fluorescent labels. Four sequencing reaction products of a sample can be electrophoresed in the same lane, thereby reducing the effect of mobility differences between sequencing lanes on accuracy. Each fluorescent label fragment is separated by electrophoresis, and at the same time, the laser detector is scanned synchronously, and the excited fluorescence is divided by the grating to distinguish the different color fluorescence representing different base information, and the image is synchronized on the CCD camera. The computer can synchronously detect the operation of the instrument during electrophoresis, and the results can be output in the form of electrophoresis map, fluorescence absorption peak map or base arrangement order. This method of sequencing is the basic principle of first-generation sequencing.
　　
High-throughput sequencing technology is a revolutionary change to traditional sequencing, which can sequence hundreds of thousands to millions of DNA molecules at one time. Second generation sequencing technology flanked the fragmented genomic DNA with linkers and then used different methods to generate arrays of millions of spatially immobilized PCR clones. At present, the technology has been developed to the third generation of sequencing technology, that is, single molecule sequencing technology.