The Kantaro COVID-SeroKlir kit is a direct ELISA for the quantitative detection of human IgG antibodies to the SARS-CoV-2 virus in serum and plasma (K2-EDTA/Li-Heparin) samples. COVID-SeroKlir has FDA Emergency Use Authorization (EUA) in November 2020 having previously received a CE mark in October 2020.
COVID-SeroKlir has demonstrated 97.8% sensitivity and 99.6% specificity for detecting SARS-CoV-2 specific IgG antibodies against two virus antigens, the full-length spike protein and its receptor-binding domain. COVID-SeroKlir is a two-step enzyme-linked immunosorbent assay (ELISA) and can be used by any certified laboratory* without the need for proprietary equipment.
The SeroKlir ELISA kit contains components to test 630 patient samples and uses standard ELISA protocols and equipment. The test comprises a two-phase ELISA, the initial plate screens for RBD positive or negative samples and the second plate provides a quantitative result of the antibody titre (concentration) using full length Spike protein.
The SeroKlir ELISA kit was developed by clinicians at the Icahn School of Medicine at Mount Sinai Health System, New York(1). The test has been trialled on a cohort of more than 70,000 patients including over 30,000 who were diagnosed with COVID-19(2).
*UKAS and ISO 15189 in UK, Rilibak and ISO 15189 in Germany. Equivalent certification required in all other countries.
|
Kit component |
Specification |
|
7 x RBD plates |
96 well polystyrene microplate coated with recombinant SARS-CoV-2 Spike protein RBD antigen sufficient for 630 screening tests |
|
3 x spike plates |
96 well polystyrene microplate coated with full length recombinant SARS-CoV-2 Spike protein sufficient for 228 quantitative tests |
|
Controls |
RBD Positive Control |
|
Calibrators |
8 calibrators (range 0-200 AU/mL) |
|
Consumables |
RBD conjugate concentrate - IgG ELISA Spike conjugate concentrate - IgG ELISA Conjugate buffer - IgG ELISA Sample buffer - IgG ELISA TMB substrate - IgG ELISA Stop solution - IgG ELISA Wash buffer - IgG ELISA |
Product Code: CVD2-2019
|
Performance specifications |
|
|
Assay type |
Solid phase sandwich ELISA |
|
Format |
96 well one-piece plate |
|
Assay length |
3.5 hours (RBD ELISA) 3.5 hours (spike ELISA) |
|
Sample types |
Serum (20 uL) EDTA plasma (20 uL) Heparin plasma (20 uL) |
|
Assay range |
3.2 – 160 AU/mL |
|
Specificity |
99.6% |
|
Sensitivity |
97.8% |
‘We believe that our ELISA method will be very useful for serosurveys aimed at determining the real attack rate and infection fatality rate in different human populations, and to map the kinetics of the antibody response to SARS-CoV-2.’
‘We show that titers are relatively stable for at least a period approximating 5 months and that anti-spike binding titers significantly correlate with neutralization of authentic SARS-CoV-2. Our data suggests that more than 90% of seroconverters make detectible neutralizing antibody responses. These titers remain relatively stable for several months after infection.’
Two phase ELISA interrogating both the full length Spike protein and its Receptor Binding Domain (RBD):
Analytical sensitivity: Limit of Blank (LoB), Limit of Detection (LoD), and Limit of Quantitation (LoQ) were established according to the recommendations in CLSI guideline EP17-A2. RBD ELISA and Spike ELISA summary data is presented opposite
Positive Percent Agreement: For the positive samples confirmed with a known EUA-authorized molecular test, PPA was 97.8%. Two samples that tested negative with the COVID-SeroKlir Kantaro Quantitative SARS-CoV-2 IgG Antibody Kit also tested negative on an existing EUA approved serology test, suggesting that these were true negative samples.
Negative Percent Agreement: For the negative samples the NPA was 99.6%. There were 14 samples that tested positive on the RBD ELISA. Of these samples, 13 subsequently tested negative on the Spike ELISA. Therefore the number of negative samples was 281 out of 282.
| Sensitivity | RBD ELISA (CI) |
Spike ELISA (AU/mL) |
| LoB | LoD | LoQ |
| 0.70 | 0.82 | --- |
| 1.98 | 2.61 | 3.20 |
An initial qualitative (screening) ELISA is performed against recombinant Receptor Binding Domain (RBD) of SARS-CoV-2. Positive samples from this screen are analysed by a quantitative ELISA against full length SARS-CoV-2 Spike protein. The assay aids in establishing the quantitative levels of neutralizing antibodies indicative of an adaptive immune response to SARS-CoV-2 in patients suspected of previous SARS-CoV-2 infection, or for the detection of IgG seroconversion in patients following known recent SARS-CoV-2 infection.
Determination of the number of individuals who are demonstrated to have developed specific antibodies to SARS-CoV-2 aids in the determination of seroprevalence in any geographic region or group of exposed individuals and may be indicative of the potential risk of reinfection. The results of the assay correlate with the neutralization of SARS-CoV-2 virus in vitro.
Results from the COVID-SeroKlir Kantaro Quantitative SARS-CoV-2 IgG Antibody Kit should not be used as the sole basis for diagnosis and should not be used for the diagnosis of patients with acute COVID-19 infection.
Results are for the detection of SARS-CoV-2 IgG antibodies. IgG antibodies to SARS-CoV-2 generally become detectable at 10-14 days following infection but may occur later. The presence of IgG antibodies, following previously negative testing, defines IgG antibody seroconversion following SARS-CoV-2 infection.
Negative results do not preclude acute SARS-CoV-2 infection and should not be used as the sole basis for patient management decisions. IgG antibodies may not be present for more than two weeks following infection, and patients may remain infectious during acute infection even if IgG antibody is present. Results must be combined with clinical observations, patient history, and epidemiological information. The sensitivity of the COVID-SeroKlir Kantaro Quantitative SARS-CoV-2 IgG Antibody Kit early after infection is unknown.
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