Should the sampling swabs used for coronavirus nucleic acid detection and antigen detection be sterilized? Why does it turn yellow?

       In the current epidemic situation, the detection of covid-19 nucleic acid and antigen is indispensable. I believe everyone has a lot of contact with the small sampling swab during nucleic acid and antigen detection. However, many people are still worried about whether the small sampling swab has been sterilized. Why does the swab turn yellow and will it affect us?

       Sampling is the first step of testing. Many friends have questions about whether the disposable sampling swab is “sterilized” or “non sterilized”, and whether it needs to be sterilized. Let’s take a look at these questions

1. What material is generally used for sampling swabs?

      Disposable collection swabs are different from cotton swabs used in daily life and belong to medical device products.

      Common sampling swab head materials include flocking, sponge, etc. It shall have the characteristics of easy elution, no toxic effect on pathogens and contacted cells and tissues, and no impact on subsequent detection.

2. What is “sterile” and what is “non sterile” / “non sterile”

       [sterility]: refers to the state without viable microorganisms. After sterilization, the theoretical probability of the existence of viable microorganisms should not exceed the negative 6th power of 10. Therefore, in some use environments with high requirements, “sterile” medical devices are required.

       [non sterile / non sterile]: Although this kind of medical devices can not be as strict as “sterile” medical devices, which are almost “free of bacteria”, they are not “dirty”. All medical devices must meet certain health requirements, such as strictly controlling the number of microorganisms, before they can be qualified for marketing.

      The sampling head is the core part of a disposable sampling swab. Take it as an example, the sampling head of a common cotton swab can be made of medical absorbent cotton, polyester staple fiber, electrostatic flocking fabric and other materials. If the “non sterile” medical absorbent cotton is used, it must comply with the Chinese pharmaceutical industry standard medical absorbent cotton. The manufacturer must provide the microbial limit for the reference of medical institutions and other users.

3. Will the sampling swab with “bacteria without sterilization” affect the antigen detection?

      This is a misunderstanding caused by confusing bacteria and viruses.

      It should be noted that the antigen detection “looks for” the N protein of novel coronavirus carried by the covid-19 infected person. The display window of the reagent strip contains an antibody that can recognize the viral protein, which is like a dam. It can only intercept the antibody latex / colloidal gold conjugate that binds to the viral antigen, and present it in the form of antibody antigen antibody latex / colloidal gold (referred to as double antibody sandwich method) so as to develop color in the display window. Therefore, even if the sampling swab carries “bacteria”, the detection reagent card will “ignore” and focus on finding the N protein of novel coronavirus carried by the coronavirus infected person. Since the reagent card is not interfered by “bacteria”, the result of antigen detection will not be affected.

4. Is it necessary to sterilize the “non sterilized” / non sterilized “sampling swabs before use?

      It is not recommended to use household disinfectant to disinfect the sampling swab head. The disinfectant may have the risk of destroying the sampling sample, thus affecting the original test results. The sampling swab is a medical device product, which is used to scrape the cells and virus samples into the extraction solution / virus preservation solution for relevant detection. The qualified sampling swab is non-toxic and harmless.

5. Why are some sampling swabs “yellow”, and how is it caused?

      As mentioned above, some sampling swab heads are made of sponge (also known as polyurethane foam), which will cause thermal oxidation yellowing under light (UV) and high temperature conditions or gas fumigation yellowing caused by contact with nitrogen oxides (NOx) in the air due to the characteristics of the swab materials. This is an inevitable phenomenon in the current production process of polyurethane foam, so it is recommended to store it at 2-30 ℃ away from light to avoid or slow down yellowing.

 Sampling swabs and nucleic acid detection, antigen detection cotton swabs, and their sterilization are briefly introduced

      We should all know whether we are infected with novel coronavirus. In addition to nucleic acid, we can also use antigen self-test. The sampling swab and cotton swab used for testing are common medical devices.

      Brief introduction of swab sampling with cotton swab for nucleic acid detection and antigen detection

   the sampling swab can be used to collect oral epidermal cells or nasal virus samples, and then the cells or samples are stored in the collection tube and transferred to the laboratory for testing, so as to realize the detection of human oral or nasal diseases. Different from the cotton swabs used in daily life, the sampling swab shall ensure the sampling amount and release amount, and the selected materials shall not affect the subsequent detection. The swab is mainly composed of a sampling head and a medical ABS plastic rod. The material of the sampling head is closely related to the subsequent detection.

       Flocking swab made of nylon fiber through spray technology.

   the sampling swab head should be made of polyester (PE) synthetic fiber or rayon (artificial fiber), and calcium alginate sponge or wooden swab (including bamboo swab) cannot be used. The swab head should not be made of cotton products, because cotton fiber has strong adsorption on protein and is not easy to elute into the subsequent preservation solution; However, the broken wooden stick or bamboo stick containing calcium alginate and wood components will also absorb protein when soaked in the preservation solution, and even inhibit the subsequent PCR reaction. 

        Brief introduction of nucleic acid detection, antigen detection, swab sampling and swab sterilization

   sampling swabs are usually sterilized by EO (ethylene oxide sterilization) or irradiation, but EO, as a carcinogen, is extremely harmful to human health. For EO sterilized swabs, some people worry about whether EO will remain on the swabs and enter the human body during detection. However, there is no need to worry. The EO sterilized swabs will be analyzed for 14 days, and the EO residue can only be delivered after passing the test. Moreover, it will be naturally analyzed during the circulation process. The EO residue of the sampling swabs that reach our hands will not affect human health.

       How to correctly select a disposable virus sampling tube? Pay attention to the following aspects:

1. Swab

   flocking swab, as a sample collection tool, has the advantages of high sample collection rate, good adsorption and not easy to shed wool, which is not available in cotton swabs, and can collect samples well.

2. Virus storage tube

   general name of virus sampling tube disposable virus sampling tube is generally used for the detection and sampling of infectious pathogenic microorganisms by disease control departments and clinical departments. It is applicable to the detection and sampling of influenza virus (including general influenza, highly pathogenic virus, influenza A (H1N1), hand, foot and mouth virus, novel coronavirus, measles, rubella and other types of viruses. VTM virus sampling tube can also be used for detection and sampling of mycoplasma, chlamydia and Ureaplasma urealyticum.

       Generally, the virus sampling tube is equipped with a disposable flocking swab. From the appearance, the flocking swab is white and soft. Using this soft brush during the sampling process will make the user feel no foreign matter, and it is suitable for people sampling at different parts. Moreover, the flocking swab is designed with a break point that conforms to the length of the sampling tube and the natural lumen of the human body, which is not only convenient for sampling but also convenient for specimen transportation.

   the virus sampling tubes are loaded with infectious substances, and some are even highly pathogenic substances. Therefore, the requirements for packaging containers are very strict, and the requirements in three aspects should be met at the same time

(1) Transportation safety.

   ensure that the sample does not leak during transportation. Sampling tubes complying with who regulations and biosafety regulations.

(2) , security of storage.

   ensure that the sample does not leak during storage. Sampling tubes complying with who regulations and biosafety regulations.

(3) . validity of samples.

   ensure that the sampling tube itself will not have toxic effects on the sample.