Diagnosis is critical to the response to the COVID-19 pandemic. At present, there are three main methods for detecting the COVID-19 infection, including molecular detection represented by PCR nucleic acid detection (detecting viral RNA), rapid antigen detection (detecting viral protein) and antibody detection (detecting IgG and IgM antibodies). As our understanding of the COVID-19 continues to deepen and the epidemic situation continues to change, the roles of different COVID-19 diagnostic methods in clinical and epidemic prevention and control are also quietly evolving.
PART 01
The three have their own advantages, limitations and applicable scenarios
With the development of the epidemic, appropriate joint testing is an important trend.
1.Nucleic acid testing: for diagnosis and as a basis for initiating public health measures.
2.Antigen detection: simple operation, fast results and low cost. It can be used to rapidly screen high-risk individuals and promote social activity recovery.
3.Antibody testing: Can be retrospectively monitored for infection or vaccination to inform public policy. However, the association with individual protective effects needs further study.
There is no perfect method, and each of the three types of detection has its own strengths. Although sensitivity and specificity are important attributes of detection methods, obtaining correct diagnostic results also depends on the stage of infection at the time of sampling, sampling quality, and proficiency in the operation.
PART 02
The impact of infection signatures on detection strategies
1. Asymptomatic and presymptomatic populations: High concentrations of virus can be detected in the nose of infected individuals regardless of their clinical presentation. This feature means that testing people with symptoms alone is not enough to control the spread of the virus.
2. Duration of contagiousness: COVID-19 nucleic acid can be detected as early as 6 days before the onset of symptoms, peaks at the onset of symptoms or a few days later, and is usually no longer detectable from upper respiratory tract samples about 2 weeks after the onset of symptoms. Viral loads in lower respiratory tract samples may be higher, peak later, and last longer. The risk of infection is mainly concentrated from 2 to 3 days before the onset of symptoms to 8 days after the onset of symptoms.
3. Virus mutation: Due to the instability of RNA viruses, the new coronavirus will mutate during the replication process. Some mutations may result in increased transmissibility, increased virulence, or altered clinical manifestations of disease; or reduced effectiveness of public health and social measures or existing diagnostics, vaccines, and treatments.
4. Human immune response: After infection with the new crown, both humoral and cellular immune responses occur within 1-2 weeks after symptoms appear. The humoral immune response mainly produces antibodies and targets viral surface proteins, while the cellular immune response targets a wider range of viral proteins. After COVID-19 infection, IgM and IgG antibodies peaked on days 11-14 after symptoms appeared, and IgM and IgG antibodies tended to appear almost simultaneously. The use of IgM antibody detection in combination with molecular testing can increase the detection of people who do not seek medical treatment in time.
5. Duration of immunity and risk of reinfection: Reinfection with respiratory viruses is common as immunity declines. So far, there is little evidence that COVID-19 antibodies confer durable immunity to reinfection. As mutant strains emerge, monitoring for reinfection is critical.
PART 03
COVID-19 detection strategy needs to be continuously adjusted
With the different stages of the development of the epidemic, the strategy of COVID-19 detection also needs to be continuously adjusted.
1.Early stage of the epidemic: Nucleic acid testing was used as an important standard for diagnosing new crown infection in the early stage of the epidemic, providing a strong guarantee for epidemic prevention and control.
2.Several months after the outbreak：Scientists found that a significant proportion of transmission cases (over 20%) can be attributed to asymptomatic and incubation period infections. As a result, epidemic prevention and control strategies have changed, such as blocking community transmission by expanding the scope of nucleic acid testing populations, tracing close contacts, and isolating and controlling.
However, due to the limited number of professional technicians and testing reagents, it is challenging to carry out large-scale laboratory nucleic acid testing. How to quickly screen suspected patients and close contacts through diversified testing methods has become the focus of attention.
3.After the COVID-19 epidemic is normalized: In the context of resumption of work and production, we can perform antigen detection and analysis through high-throughput laboratory analysis, and can also quickly read the analysis results through antigen detection kits. Compared with nucleic acid testing, kit-based rapid diagnostic testing is more convenient and faster, which helps to improve the detection rate of positive patients, but has relatively low sensitivity and can be used as an important supplement to nucleic acid testing.
PART 04
Hecin’s COVID-19 Detection Solution
Changes in the epidemic have stimulated the development of various testing methods. In different environments, choosing a specific testing strategy requires a comprehensive consideration of testing purposes and available resources, as well as balancing accuracy, accessibility, affordability, and testing speed requirements.
Since 2020, Hecin has paid close attention to the prevention and control of the novel coronavirus pneumonia, and 2019-nCoV Nucleic Acid Test Kit (PCR- fluorescence probe method)、2019-nCoV Antigen Test Kit(colloidal gold method)、2019-nCoV IgM/IgG Antibody Test Kit (colloidal gold method) have been produced successively to provide strong support for the global fight against the epidemic.
2019-nCoV Nucleic Acid Test Kit (PCR- fluorescence probe method)
2019-nCoV Antigen Test Kit(colloidal gold method)
2019-nCoV IgM/IgG Antibody Test Kit (colloidal gold method)
Hecin’s COVID-19 detection solution always guarantees the specificity, accuracy and sensitivity of products, and continues to serve the prevention and control of COVID-19 in many countries and regions around the world.
