COVID-19 IgG Novel Coronavirus ELISA Test System

INTENDED USE
The Monocent, Inc.’s COVID-19 IgG ELISA Test System is intended for the qualitative detection of human anti-COVID19 IgG antibody in human serum.
This ELISA Test System is used as an aid for the detection of novel COVID-19. Patients with suspected clustering cases require diagnosis or differential diagnosis of novel coronavirus infection.

SUMMARY AND EXPLANATION
2019 novel coronavirus (COVID-19) is a single-stranded RNA coronavirus2. Comparisons of the genetic sequences of this virus have shown similarities to SARS-CoV and bat coronaviruses7. In humans, coronaviruses cause respiratory infections3. Coronaviruses are composed of several proteins including the spike (S), envelope (E), membrane (M), and nucleocapsid (N)4. Results suggest that the spike protein retains sufficient affinity to the Angiotensin converting enzyme 2 (ACE2) receptor to use it as a mechanism of cell entry6. Human to human transmission of coronaviruses is primarily thought to occur among close contacts via respiratory droplets generated by sneezing and coughing1. IgG is the most abundantly found immunoglobulin to be produced in response to an antigen and will be maintained in the body after initial exposure for long term response5.

PRINCIPLE OF THE TEST
Monocent, Inc.’s ELISA Test System is designed, developed, and produced for the qualitative measurement of the human anti-COVID-19 IgG antibody in serum. This assay utilizes the microplate based enzyme immunoassay technique.
Assay controls and 1:100 diluted human serum samples are added to the microtiter wells of a microplate that was coated with COVID-19 recombinant full length nucleocapsid protein. After the first incubation period, the unbound protein matrix is removed with a subsequent washing step. A horseradish peroxidase (HRP) labeled polyclonal goat anti-human IgG tracer antibody is added to each well. After an incubation period, an immunocomplex of "COVID-19 recombinant antigen – human anti-COVID-19 IgG antibody - HRP labeled anti human IgG tracer antibody" is formed if there is specific coronavirus IgG antibody present in the tested specimen. The unbound tracer antibody is removed by the subsequent washing step. HRP-labeled tracer antibody bound to the well is then incubated with a substrate solution in a timed reaction and then measured in a spectrophotometric microplate reader. The enzymatic activity of the tracer antibody bound to the anti-COVID-19 IgG on the wall of the microtiter well is proportional to the amount of the anti-COVID-19 IgG antibody level in the tested specimen.PERFORMANCE CHARACTERISTICS
Limit of Detection: The limit of detection is not higher than 5 U/mL.
Repeatability: The assay control is tested in 10 replicates with a CV of OD values less than 15%.
Reproducibility: Three lots were tested with the same samples 10 times with a CV less than 20%.

CLINICAL TESTING
Serum samples from two cohorts of patients were tested using the IgG ELISA Test System at the Jiaxing City Center for Disease Control and Prevention and Zhejiang University Hospital. The combined cohort consisted of normal healthy patients with samples collected prior to the COVID-19 outbreak [December 3, 2019] (n = 54) and RT-PCR confirmed positive patients in after the second week of the onset of the disease (n = 30). The results are as follows:

The diagnostic sensitivity is 100%.
The diagnostic specificity is 100%.