Coronaviruses were once taken as a group of pathogens that cause no or slight self-healing diseases in humans, which, however, have ignited several worldwide prevalences in the first 20 years of the 21st century, that is, severe acute respiratory syndrome in 2002-2003, Middle East respiratory syndrome in 2012 and coronavirus disease 2019 starting from December 2019.

Coronavirus is a large family. According to the characteristics of serotypes and genomes, the subfamily of coronavirus is divided into four genera: α, β, γ and δ. α and β only infect mammals, while γ and δ will mainly infect birds. So far, seven subtypes of coronavirus have been identified to infect human beings, which are human coronavirus 229E, hCoV-229E, hCoV-NL63, hCoV-OC43, hCoV-HKU1, SARS-CoV, MERS-CoV, and SARS-CoV-2.

Currently, there are 957,875 cases in the United States (last updated on April 26, 2020). Since the amino acid test (a conventional method of laboratory test in China at the beginning of this epidemic) is time consuming and laborious, the American hospitals are in urgent need of reliable and fast testing approaches. Recently, scientists have discovered that the detection of SARS-CoV-2 IgM/IgG antibodies through colloidal gold immunochromatography shows potential clinical application values.

Coronavirus encodes at least four structural proteins: spike protein, envelope protein, membrane protein and nucleocapsid protein. Antibody combines with antigen specifically. The N and S proteins of SARS-CoV-2 are the main antigen sites for combination with the specific antibodies generated by human body. After infection, the human immune system firstly produces the IgM antibodies usually within one week, to suggest a recent infection. While, the IgG antibodies are generated later, but exist for a long time in vivo, the index of previous infection. Simultaneous detecting IgM antibodies and IgG antibodies can distinguish acute infection from previous infection, which provides exacter result and cut down the influence caused by viruses’ window period.

The SARS-CoV-2 IgG/IgM detection kits (CE-conform) (Colloidal Gold Method) receive high popularity among hospitals worldwide because of the simple operation, precise and fast outcome, whose working principle lies in the combination of IgM/ IgG with colloidal gold-labeled novel coronavirus antigen on the test cassette. It can be adopted as a supplementary and cooperative detection index for the suspected whose nucleic acid tests are negative.

Creative Biolabs, one of the many biotechnology companies distributing in vitro diagnostic kits for SARS-CoV-2 that operate with peoples whole blood, serum, and plasma, updates its products list, offering broader options to global researchers & hospitals to simplify the test process, and to meet various experiment purposes.
Fluorescent RT-PCR method-based detection kits
ELISA based detection kits
Colloidal Gold Method based detection kits

It is also believed that combined detection of IgM/IgG antibodies and viral nucleic acid can give full play to their advantages, not only to ensure rapid detection, but also to improve clinical accuracy. Colloidal gold method has satisfactory sensitivity and specificity, whose coincidence rate of detection results of homologous whole blood, plasma or serum samples is 99%, offering reliable insights to the clinical screening of suspected cases/cases with negative nucleic acid detection result, population epidemiological investigation, identification of acute infection and previous infection, and clinical judgment for retrospective diagnosis, prognosis and recovery.