The difference of commonly used test methodology in infectious disease diagnosis

Veterinary tests mainly include the following detection methods: colloidal gold rapid diagnostic technology, enzyme-linked immunosorbent assay (ELISA), immunofluorescence technology (IF), nucleic acid detection.
1.Colloidal gold (immunomethodology)
The colloidal gold immunochromatography technique is used to detect the toxin content in the sample by capillary action, which makes the sample solution reach the specified position and react with color. During detection, the toxin in the sample binds to a specific antibody labeled with colloidal gold, which inhibits the binding between the antibody and the toxin conjugate on the detection line (T-line), resulting in a change in the color of the T-line, and the content of the toxin is judged by the depth of the color of the T-line.
Regardless of the content of toxins in the sample, the quality control line (C line) is colored to show that the detection is effective.
2.ELISA (Immunomethodology)
ELISA test can be used to determine antigens, but also can be used to determine antibodies. There are three necessary reagents in this method of determination:① Solid phase antigen or antibody; ② enzyme labeled antigen or antibody; ③ Substrate of enzyme action (chromogenic agent).
According to the source of reagents, the properties of specimens and the conditions of detection, various types of detection methods can be designed. Interested friends can further understand, such as double antibody sandwich method, double site one-step method, indirect method to measure antibodies, competition method, capture method to measure IgM antibodies and so on.
  1. 3.Immunofluorescence (immunomethodology)
The antibody is labeled with a fluorescent substance, the antigen in the sample reacts with the labeled antibody, and the amount of antigen is determined by detecting the fluorescence intensity of the conjugate. This technology is called fluorescence immunotechnique. Immunofluorescence chromatography is a novel membrane detection technology based on antigen-antibody specific immune response. In this technique, a strip of fiber chromatography material with a fixed detection line (coated with antibody or coated with antigen) and a quality control line (anti-antibody) is used as the stationary phase, and the test liquid is used as the mobile phase. The fluorescently labeled antibody or antigen is fixed on the connecting pad, and the analyte is moved on the chromatographic strip through capillary action.
The reagent structure of P.S. immunofluorescence chromatography is very similar to that of gold standard immunochromatography, both of which are typical lateral flow immunochromatography strips. The main difference between the two is that the marker used is different, gold particles are the marker for gold immunochromatography, and fluorescein is the marker for fluorescence immunochromatography.
In clinical application, colloidal gold is generally qualitative detection, and immunofluorescence is quantitative detection, the latter is higher in the sensitivity of detection.
4.Nucleic acid Testing (Molecular diagnostic methodology)
The full name of molecular PCR is "polymerase chain reaction", which is actually a reaction that expands the DNA sequence. To put it bluntly, the obtained DNA fragments are enlarged to highlight the properties inside for identification.
In fact, the principle of nucleic acid detection is just an additional operation on the basis of the above part: the fluorophore is added to the PCR amplification system. When the fluorophore is in the complex state, there will be luminescent groups and quenching groups, and it will not fluoresce when the target DNA strand is not encountered. However, in our sample, if there is a certain amount of target DNA strand, the quenching group of the structure of this complex will be destroyed in the process of reciprocating single and double strand transformation during PCR amplification, and then the remaining luminescent group will emit fluorescence quantitatively, so that the content of DNA strand in the original sample can be calculated according to the curve of the amount of fluorescence emitted.
Brief summary
Among the above-mentioned virus detection methods, colloidal gold rapid diagnostic technology, elisa diagnostic test (elisa) and immunofluorescence technology (IF) are all immunoassay detection based on protein level, while nucleic acid detection is molecular diagnostic methodology detection based on genetic material. Different detection methods have different detection targets. Therefore, each method has a suitable application scenario in clinical practice.
However, the diagnosis of all diseases cannot be based on a single test result. The results of the IVD test can be affected by various clinical factors, so it is only recommended as an adjunct diagnosis. In the case of the most well-known novel coronavirus, the use of antigen detection is only an auxiliary means. In order to make the final diagnosis, it is necessary to isolate the high-risk groups for observation, and make a comprehensive judgment according to their clinical symptoms and imaging results. Veterinary rapid test of hysen helps you to better detect and protect the health of animals.

Post time:2024-01-25
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