The enzyme-linked immunoassay, or ELISA for short, centers on allowing antibodies to bind to enzyme complexes, which are then detected by color development. Steps: ELISA is detected with serum, first the blood should be agglutinated for at least half an hour, then the serum will be taken to dilute the enzyme complex with diluent, add serum and negative and positive control, and also the quality control. After an hour of incubation, the plate is washed, the substrate is added, and the reaction is completed by adding the termination solution after half an hour of light-proof reaction, and then it is read. The value is used to determine whether the result is negative or positive.
Classification
Serological test > Serological test for viruses
Principle of measurement
ELISA: A carrier encapsulated with inactivated rubella virus antigen can bind to specific antibodies in the sample under test, and the corresponding antibody is detected with enzyme-labeled anti-human immunoglobulin and substrate.
Reagents
Same as general ELISA except for inactivated rubella virus antigen-coated microtiter plate and negative and positive reference sera.
Operation method
1. Sample collection, only a single blood sample should be collected for the screening test, but if the immune status of the infected person needs to be determined, samples should be taken from suspected rubella patients within 3 days of the appearance of the rash and the following 14 to 21 days for simultaneous testing.
2, as in the general ELISA, add 50 μl of PBS to each well of the control and sample, followed by 10 μl of sample, hold at 25°C for 45 min, wash and aspirate.
3.Add 250μl of enzyme marker to each well, keep warm and wash in the same way.
4.Add 250μl of pNPP substrate solution, hold and wash in the same way, then add 50μl of 1mol/L sodium hydroxide to abort the reaction, measure the absorbance value of each well at 405nm, and judge the result of the sample being tested.
5.If the result is positive, the sample can be further diluted for antibody titer determination, compare the results of the two successive samples, and make a judgment
Determination
1, rubella virus IgG and lgM antibodies are positive, or IgG antibody titer ≥ 1: 512, indicating a recent infection with rubella virus.
2, Both IgG and IgM antibodies to rubella virus are negative, indicating no previous rubella virus infection.
3, rubella virus lgG antibody titers <1_512 and lgM antibodies are negative, indicating a history of previous infection.
4, In addition, re-infection with rubella virus is not easily detected because only transient IgM antibodies appear or appear at very low levels. Therefore, a rubella virus IgG antibody titer that is more than 4-fold elevated in a double serum is an indicator of recent rubella virus infection, regardless of whether the lgM antibody is positive.
Clinical significance
Rubella, also known as German measles, has a peak incidence in the spring to early summer. The rate of positive rubella virus antibodies increases with age, and newborns can acquire IgG antibodies to rubella virus through their mothers who were infected with the virus earlier in life. lgM antibodies are produced about 4 days after the onset of the rash, peaking at about 10 days and lasting 6-12 weeks or occasionally up to a year; IgG antibodies appear slightly later than lgM antibodies and gradually increase, peaking at 1 to 2 months. IgG antibodies appear a little later than lgM antibodies and gradually rise, peaking at 1 – 2 months and then declining, mostly for life. 80% of the population is positive for this antibody.
Measurement
Normal range: Negative anti-rubella virus antibody IgM, negative anti-rubella virus antibody IgG.
Test description: Anti-rubella virus antibody IgM is mainly used to diagnose acute infection with rubella virus, and anti-rubella virus antibody Ig usually appears in the serum 2 weeks after infection.
Clinical significance: Positive: Rubella virus infection.