Frequently Asked Questions

Q: I read that Spain rejected a lot of tests and found that they were "inaccurate" -- is this true? How are yours different? How can I feel comfortable with these?

 A:There must be differences in the accuracy of products from different manufacturers. The sensitivity of Bioeasy Antigen Test Kit product mentioned in the Spain news cannot represent other similar products. The accuracy of this kind of antigen test kit is highly dependent on the specificity of the antibody. If the quality of the antibody is not good, it is easy to have cross-reaction resulting in misjudgment. By now, there is no antigen test kit product certified by NMPA (National Medical Products Administration)1 since its sensitivity and accuracy is still limited with current R&D status. So antigen test kit was not approved to be sold in Chinese market currently 2.


All products we sell are certified by NMPA (National Medical Products Administration). By now there are only five kinds of 2019-nCoV lgG/lgM Detection Kit (Colloidal Gold-Based) products got the certification from NMPA (National Medical Products Administration)3. This certification ensures the safety and effectiveness of COVID19 Rapid Test kit products.

Q: How accurate are the COVID19 IgG/IgM Antibody rapid test kit you sell?

A:Based on the Diagnostic Performance Evaluation and Clinical Validation Data Summary, the combined statistical analysis of the combined detection results of this lgG/lgM Detection Kit showed that the combined clinical sensitivity of one product – Vazyme – was 91.54% (95% CI: 86.87%, 94.65%) and combined specificity was 97.02% (95% CI: 94.74%, 98.33%)4. The combined sensitivity of another product – Livzon – was 90.2% (95% CI:86.2%,93.1%) and combined specificity was 99.2% (95% CI: 97.6%, 99.7%). It means that we could get more than 90% positive detection results in total confirmed cases and more than 97% negative detection results in total excluded cases with our lgG/lgM Detection Kits.

Q: When should they be used? When not?

A: The premise of positive antibody detection is that the human body has been infected and has an immune response. When the human body contacts with antigens, the first antibody produced is IgM, but it also needs to be about a week after the body responses for the pathogen stimulation. According to the trial 7th edition of China's COVID19 diagnosis and treatment guideline, the IgM will usually be positive after paroxysm for 3-5 days 5. The level of IgM antibody begins to rise after 1 week after the initial infection, while the IgG appears later than IgM (usually in 14 days after infection) and can last for 6 months or even several years, which means that the IgG serves as an indicator of previous infection. The window gap of detection from virus replication to antibody production will result in lagging behind the time of PCR detection.


Antibody detection has limitations (window period) when it is applied to the screening of early infected and latent infected persons. It cannot replace the early screening of PCR detection, but as an auxiliary judgment method when the suspected patients are finally diagnosed or excluded 6.

IgG/IgM antibody test will help to trace in a much more population-based way who has had the infection, because many cases seem to be spread from asymptomatic patients who can’t be identified easily.

Q: What is the difference between Antigen rapid test kit vs IgG/IgM Combo Antibody rapid test kit because both can have resulted in 15 minutes?

A:The novel coronavirus genes encode multiple structural proteins, such as Protein N, Protein E and Protein S. These proteins include multiple epitopes. Novel coronavirus can be directly detected in samples via detecting the presence of antigens by antibodies based on the principle of antigen binding with antibody. The applicable sample type of antigen test kit is the sample of infected respiratory system part, such as throat swab.


The above antigens of novel coronavirus can be used as immunogen and stimulate immune system to produce specific antibodies after the virus infects the human body. Novel coronavirus can be indirectly diagnosed via detecting the presence of antibodies by antigens based on the principle of antigen binding with antibody. The applicable sample type of antibody test kit is generally blood, including serum, plasma and whole blood.


The key of good antigen / antibody detection reagent is to obtain highly sensitive and specific antigen and antibody for detection. However, the antibody developing process is more difficult and time-consuming. So far there is no ideal antibody developed, so no antigen rapid test kit has been certified by NMPA (National Medical Products Administration) yet. While recombinant antigen technology is relatively fast, but it also needs time and experimental evidence to select the best antigen 7. The safety and effectiveness of COVID19 IgG/IgM Combo Antibody rapid test kit products can be ensured by the NMPA (National Medical Products Administration) certification.


Q: How do they compare to the throat swab style rt-PCR?

A: These real-time PCR test kits, looking for genetic material of the virus, for instance in nasal, throat, or anal swabs, suffer from many limitations 8:

  1. These tests have long turnaround times and are complicated in operation; they generally take on average over 2 to 3 hours to generate results.

  2. The PCR tests require certified laboratories, expensive equipment and trained technicians to operate.

  3. There are some numbers of false negatives for rt-PCR of COVID-19. It may due to low SARS-CoV-2 viral load in the upper respiratory swab specimen (Novel coronavirus mainly infects the lower respiratory tract, such as pulmonary alveoli)9.


PCR test only give a positive result when the virus is still present. The tests can’t identify people who went through an infection, recovered, and cleared the virus from their bodies. In real clinical experience, only about 30%-50% was positive for PCR in patients with clinically diagnosed novel coronavirus pneumonia. Many novel coronavirus pneumonia patients cannot be diagnosed because of negative nucleic acid test, so they cannot get the corresponding treatment in time.


Both IgM and IgG are immunoglobulin which are produced by the immune system to provide protection against the 2019-nCoV. Some patients with negative results in nucleic acid test show positive in IgM test, indicating that the IgG / IgM detection is one of the effective methods for the diagnosis of 2019-nCoV.

In clinical practice, the accuracy of PCR detection is also affected by many factors, such as the body location of sample, the way of sample preservation and the difference of kit, which cannot be regarded as the "gold standard" of 100% accuracy as well. 2019-nCoV lgG/lgM Detection Kit (Colloidal Gold-Based) product is suitable for combined detection with nucleic-acid testing kit to improve the diagnosis rate of suspected patients 10.


A few advantages of IgG/IgM detection compared with PCR test are listed as below:

  1. Indicating both recent infections and previous infections, reducing missed detection rates.

  2. Low requirements of instruments; suitable for primary hospitals and conventional outpatient clinics.

  3. Blood testing; low requirements for sampling; no special virus collection tube required.

  4. Suspected patients that are infected by 2019-nCoV can be rapidly identified by simultaneous monitoring of IgM and IgG.


Q: Why are your products better than Cellex which is listed in FDA?

A: It is much easier for a product to be listed in FDA if they apply under Emergency Use Authorizations (EUA), since they only need to submit necessary documents to FDA. The accuracy of this product may not be validated by large enough samples, especially clinical practice samples. Our products are all certified by NMPA (CFDA), which is stricter and more prudent in giving authorizations.


Besides, according to the recent export restrictions, only products with NMPA (National Medical Products Administration) can be exported 11/12. However, Cellex’s product hasn’t been listed in NMPA (CFDA) by now so they will have issue to export, unless there are ready stock outside of China already prior the latest regulation became effective in April 1st, 2020.


Q: Livzon products have separated the cassette between IgG and IgM. What is the difference between this and the combined IgG/IgM kit?

A: Separated IgG and IgM test kit can be used separately for different testing purpose. The lgM test kit is more suitable for identify early-age infected case while the lgG is usually used to monitor the course of disease in clinical practice. The combined IgG/IgM kit can test both antibodies at one shot, which is more convenient for screening among population.


With high demand and limited supply currently for this type of rapid testing, we would encourage you to be open for both options based on the production pipeline, as it serves the same purpose. Otherwise you might have to wait for a long time to get the specific product.


Q: How does the recent export restrictions announced on 1st Apr impact to the rapid test kit?

A: According to the recent export restrictions, only products with NMPA (National Medical Products Administration) can be exported 11/12. Not only that they have stricter requirement to be approved by NMPA, the customs bureau will do more thorough documentation and physical screening (including sampling) for every batch of goods ready to be exported. This is the reason that the export customs clearance will take longer (at least 1 week) to ensure that the product meets the quality required.













© 2020 by PureLiving Proudly created with