! This test requires professional lab infrastructure and staff and has to be ordered and administered by medical professionals. The test cannot be performed by private individuals and we do not sell the kits to such individuals. If you suspect you are infected with SARS-CoV-2, please contact your healthcare provider.

The Gold Standard Diagnostics SARS-CoV-2 IgA ELISA Test Kit is intended for the qualitative detection of IgA antibodies to SARS-CoV-2, the virus responsible for the novel Coronavirus (COVID-19), in human serum.

Coronaviruses are a family of enveloped, single-stranded positive RNA viruses that can be infectious to humans and a wide-array of animals frequently causing respiratory infections in humans.  There are four sub-families of Coronavirus: alpha, beta, gamma, and delta.  The alpha and beta subfamilies primarily infect mammals—such as humans and bats—while the gamma and delta subfamilies primarily infect birds.  There are currently 7 known strains of human-infecting coronaviruses; 4 are mild and 3 can potentially cause severe illness.  Clearly, SARS-CoV-2 is one of the strains capable of causing serious illness.

The Coronavirus family is made up of multiple components. The viral envelop serves as the anchor for the membrane (M), envelope (E), and spike (S) structural proteins.  The surface spikes, which give the coronavirus their namesake corona, are composed of a homotrimer of the S protein components S1 and S2, mediate receptor binding and fusion with the host cell membrane.  Inside the viral particle, there is the RNA genome bound to multiple copies of the nucleocapsid (N) protein arrayed in a bead-on-a-string conformation.

Unlike many other assays available, which use the S Protein, the Gold Standard Diagnostics SARS-CoV-2 IgA ELISA Test Kit uses the N protein as antigen for the detection of antibodies to SARS-CoV-2.  The N protein is more conserved than other proteins of the virus meaning that mutant forms of the virus are less likely to affect the N protein and the body’s immune response to the N protein is often greater than the response to the S protein (Burbelo 2020).  Early fears that the N protein would see high cross-reactivity with N proteins of other Coronaviruses have not born out (de Assis 2020; Grzelak 2020; Guo 2020).

In contrast to IgM and IgG, IgA antibodies are the major antibody class secreted into the mucosal membranes (saliva, gastrointestinal tract, and the respiratory epithelium).  It is often regarded as the first line of defense for respiratory pathogen and is then to be expected that this class of antibody play an important role in host defense during, and following, a SARS-CoV-2 infection.

In addition to its function as a secreted antibody, IgA can also be detected in the serum.  IgA has been reported in SARS-CoV-2 infection as early as IgM and, interestingly, seems to be more pronounced than IgM.  Case studies have also indicated that IgA levels may be indicative of disease severity.  Including IgA detection for the serological assessment of COVID-19 is likely to have potential importance.

Ready-to-Use Liquid Reagents

Results in under 2 hours

1 Month stable reagents after opening if stored at 4oC

Lot specific Calibrator Value to normalize lot-to-lot variation

Sensitivity of 88.9% at 12 or more days following onset of symptoms

Specificity of ~100%

Entire protocol carried out at Room Temperature

96 Well Breakable Microtiter Plate coated with SARS-CoV-2 Antigen

Ready to use Dilution Buffer, 2×50 mL

20X Wash Concentrate, 50 mL

Ready to use Negative Control, 1.5 mL

Ready to use Calibrator, 1.5 mL

Ready to Use Positive Control, 1.5 mL

Ready to Use Conjugate IgA, 13.5 mL

Ready to Use Substrate Solution, 13.5 mL

Ready to Use Stop Solution, 7.5 mL

The OD of the Blank should be <0.150

The OD of the Calibrator should be greater than the negative control

The OD of the Blank should be subtracted from all other OD values

The Cutoff is determined by multiplying the Calibrator by the Correction Factor (supplied on the Calibrator vial)

               Cutoff = OD Calibrator x Correction Factor

               Units = (OD Sample / Cutoff) *10

Units are a qualitative value determined by the manufacturer

Burbelo D. et al. (2020) Detection of Nucleocapsin Antibody to SARS-CoV-2 is more sensitive than antibody to spike protein in COVID-19 Patients.  medRxiv 2020.04.20.20071423

Grzelak L et al. (2020) SARS-CoV-2 serological analysis of COVID-19 hospitalized patients, pauci-symptomatic individuals and blood donors. medRxiv 2020.04.21.20068858

Guo L. et al. (2020) Profiling early humoral response to diagnose Novel Coronavirus Disease (COVID-19).  Clin Infect Dis.  doi:10.1093/cid/ciaa310

De Assis RR (2020) Analysis of SARS-CoV-2 antibodies in COVID-19 convalescent plasma using a coronavirus antigen microarray bioRxiv 2020.04.15.043364