What Is Antigen Test and Nucleic Acid Test?

Coronaviruses are spheres less than 100 nm in diameter surrounded by an envelope and covered with spinosomal proteins (S-proteins or S-antigens), with an inner complex of nucleocapsid proteins (N-proteins or N-antigens) and ribonucleic acids (RNA nucleic acids) in an ordered arrangement (RNP).

Antigen test: In simple terms, it is to directly detect these proteins (S protein, N protein or S+N protein simultaneously) of the virus after the coronavirus-specific antibody produced by genetic engineering is labeled with gold particles or fluorescent microspheres . This depends on the specific combination of the coronavirus antibody and the coronavirus antigen to be tested, just like the relationship between a key and a lock. A lock can only be opened with a specially matched key, which has a corresponding relationship and endows the accuracy of the test. But in our daily life, we also find that similar keys can sometimes open the same lock slowly (not so specific), but the opening is not so smooth.

Nucleic acid test: In simple terms, a characteristic fragment of the RNA of a new coronavirus is cloned and amplified to the 40th power of 2 (simply understood as an amplification of tens of billions of times) and then detected by a special machine.This reliance on the characteristic fragments of the coronavirus is similar to the personal facial recognition that is commonly used to open mobile phones today, with a one-to-one correspondence that ensures the accuracy of the test (which is also more specific than the antigen test).In addition, the nucleic acid test uses a special machine to clonally amplify the characteristic fragments of the coronavirus tens of billions of times, so that even if the sample contains only a very small amount of virus (even before the infection has multiplied and caused symptoms in humans), it can still be detected, which is not possible with the antigen test.