Hepatitis A antigen
Hepatitis A antigen is a substance that always induces the production of hepatitis A antibodies in the body. Hepatitis Avirus (HAV) is an icosahedral stereo-symmetric spherical particle with a diameter of 27-32 nm. It has no envelope and the core is single-stranded positive-stranded RNA. HAV is a hepatovirus or heparnavirus of the picornavirus family. HAV is mainly transmitted through the hand-to-mouth route, with an incubation period of 15 to 50 days, with an average of 28 days. The virus is often present in the patient's blood and feces 5 to 6 days before the patient's serum ALT rises. After 2 to 3 weeks of onset, the infectivity of serum and feces gradually disappears with the production of specific antibodies in serum. Laboratory testing of HAV allows for antigen detection.Basic Information
Specialist classification: Infectious disease examination and classification: liver function examination
Applicable gender: whether men and women apply fasting: fastingAnalysis results:
Positive indicates acute hepatitis A infection.
HAVAg is present in the feces 10 to 20 days after infection, and is usually excreted from the feces 1 to 15 days before the onset of the disease, which is difficult to capture clinically. The positive rate was 42.9% at 1 week and 18.3% at 1 to 2 weeks, and disappeared after half a month. Therefore, it is rarely used clinically. If HAVAg is positive, it indicates that the patient is infected with hepatitis A, which is early in the acute phase.
People who need to be tested:
Fever, nausea, vomiting, abnormal liver function, fatigue.Positive results may be diseases: hepatitis A precautions
Before the inspection: Do not eat anything casually, especially with alcohol and greasy things.
When checking: Relax and unwind.
Unsuitable for people: those who do not have an indication for examination should not do this check.Inspection process
1, the principle of determination of hepatitis A antigen
The sandwich ELISA method, that is, coating anti-HAV, adding serum to be tested, adding enzyme-labeled anti-HAV, adding substrate color, and measuring the OD value by a microplate reader. If a nitrocellulose membrane (NC) is used instead of a polystyrene plate, the NG-EIA method, the detection of the antigen can be enhanced, and 1 ng of HAV protein can be detected, which is equivalent to 1.5×104 virus particles.
Commercialized kits are available in China, containing anti-μ chain coated reaction plates (strips), HAV application solution, anti-HAV-HRP markers, and anti-HAVIgM negative, positive control serum, sample dilution, washing solution, bottom Reagents such as liquid and stop solution.
3, the operation method
The test should be carried out according to the kit instructions. There are two general types of kits.
(1) Three-step method: There are many operation steps in this method, and the detection is time-consuming, and there is a tendency to be gradually replaced by the two-step method.
1 Add diluted sample: Add 100 μl of 1:1000 dilution sample to the well of the coated reaction plate (strip), each experiment has an yin and a positive control, incubate at 37 ° C for 2 h, and wash the plate 3 times.
2 Add HAV: Add 100 μl of HAV to each well, transfer to 4 ° C overnight at 37 ° C for 1 h, and wash the plate 3 times.
3 Anti-HAV-HRP: Each well was added with anti-HAV-HRP 100 μl, incubated at 37 ° C for 3 h, and washed 4 times.
4 Color development: 100 μl of the substrate solution was added to each well, and incubated at 37 ° C for 15 min.
5 Stop the reaction: 50 μl of the stop solution was added to each well.
6 results were interpreted.
Visual method: colorless or slightly yellowish negative, orange color is positive.
Colorimetric method: On the microplate reader, the zero point of the reagent blank is used to measure the optical density value of each hole at 492 nm. When the sample A value/negative control A value is greater than or equal to 4, it is positive, and less than 4 is negative.
(2) Two-step operation: according to the above method, add the diluted sample to the heat preservation and washing, and add 50 μl of HAV and 50 μl of anti-HAV-HRP to each well, mix and heat at 37 ° C for 1 h, wash the plate 4 times, and then develop the same color and read the same method. result.Not suitable for the crowd
Those who do not have an indication for examination should not do this check.Adverse reactions and risks
1, subcutaneous hemorrhage: due to pressing time less than 5 minutes or blood draw technology is not enough, etc. can cause subcutaneous bleeding.
2. Risk of infection: If you use an unclean needle, you may be at risk of infection.