I believe that the general public is familiar with the self-test of neo-coronavirus antigen, so is nucleic acid preservation solution and antigen preservation solution the same as nasopharyngeal swabs? What are the specific differences?
The nucleic acid test for the new coronavirus is for the nucleic acid gene fragments inside the virus. The nucleic acid preservation solution is to protect the nucleic acid from rapid degradation in vitro so that the nucleic acid sequence can be amplified for testing purposes. There are two main categories: inactivated and non-inactivated.
Inactivating type preservation solution is a preservation solution formulated based on nucleic acid extraction lysate, and the main components are balanced salts, chelating agents, guanidine salts, surfactants, etc. There are two types of inactivating preservative solutions: one is guanidine-containing, which can denature proteins rapidly and efficiently, lyse cells to release nucleic acids, eliminate nucleolytic enzymes (RNase), stabilize viral nucleic acids, and also achieve the effect of inactivating viruses. The other is the guanidine-free type, which contains surfactant and does not cleave the capsid protein on the surface of the virus, maintaining the integrity of the virus, and the virus is not easily survived.
The non-inactivated preservation solution can retain both the protein shell of the virus and the viral nucleic acid, which maximizes the originality of the viral sample and can be used for viral culture in addition to viral nucleic acid detection. However, because the virus is not inactivated, there is a risk of infection in case of mishandling.
The Workbook for Novel Coronavirus Nucleic Acid Testing in Medical Institutions (Trial Version 2) clearly states that "population screening should select sampling tubes with virus inactivation features such as guanidine salts (guanidine isothiocyanate or guanidine hydrochloride, etc.) or surfactants. The preferred sampling tube is guanidine salt. Fever outpatient or emergency rapid test, according to the requirements of the nucleic acid detection reagents used to determine the sampling tube.
New coronavirus antigen detection is performed on proteins specific to the surface of the virus. The main components of the antigen preservation solution are low ionic strength buffers (e.g., Tris buffer, PBS buffer, etc.) and surfactants (e.g., Brij58, Triton X-100, etc.).
The main function of antigen preservation solution is to protect antigen proteins from protein denaturation or decomposition, which can react with gold-labeled specific antibodies on the test strips. The guanidine salt and other components within the nucleic acid preservation solution will denature the antigen protein, affecting the antigen-antibody reaction and preventing the formation of antigen-antibody complexes, resulting in false negative or invalid results. Therefore, there is still a big difference between the preservation solution for nucleic acid and antigen of the new coronavirus.
In addition, antigen preservation solutions from different manufacturers should not be mixed. There are significant differences in the composition of different brands of products, and the performance (specificity and sensitivity) of antigen detection reagents from various manufacturers is related to the pH of the accompanying preservation solution. The optimum pH for most chromatographic antigen-antibody reactions is alkaline, when the specificity and sensitivity of the reagents are optimal. When a non-matching sample preservation solution is used it can lead to a change in pH of the reaction environment, resulting in false positive or false negative results.
