Detecting SARS-CoV-2 specific IgG antibodies with the Kantaro Covid-SeroKlir Kit

insights from industryGary DowthwaiteSpecial Projects Co-OrdinatorEKF Diagnostics

In this interview, Gary Dowthwaite, the Special Projects Co-Ordinator at EKF Diagnostics, talks to News-Medical about the Kantaro COVID-SeroKlir Kit.

To begin, can you give us an introduction to what COVID-19 IgG antibodies are?

COVID-19 IgG antibodies are raised by the immune system in response to either infection with the SarsCoV2 virus or immunization with a SarsCoV2 vaccine.  

What are some of the current methods commonly used in their detection (such as rapid tests etc.)?

Rapid tests and ELISA are the two main tests used in the detection of SarsCoV2 IgGs. Both use immobilized antigens (RBD and Spike) to capture IgGs that recognize these proteins.

Can you tell us a bit about what an ELISA (enzyme-linked immunosorbent assay) is, and how this can be utilized in terms of COVID testing/detection?

An enzyme-linked immunosorbent assay (ELISA) is an immunological assay commonly used to measure antibodies, antigens, proteins, and glycoproteins in biological samples. The SeroKlir ELISA employs an initial qualitative or screening ELISA performed against recombinant Receptor Binding Domain (RBD) of SARS-CoV-2. Positive samples from this screen are analyzed 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.

Next, can you tell us about the Kantaro COVID-SeroKlir Kit (such as how it was developed, how it works/it’s method, and how it is used)?  

The SeroKlir ELISA kit was developed by clinicians at the Icahn School of Medicine at Mount Sinai Hospital System in New York(1) and has been used on a cohort of over 70,000 patients including over 30,000 who were diagnosed with COVID19(2).  

How does the Kantaro Covid-SeroKlir Kit differ from the other kits that are available, in particular with the accuracy it provides?  

Most ELISA kits have a similar level of sensitivity. SeroKlir is unique in that it is instrument agnostic and can be used on any brand of technology.  The test can be run in any lab with a 96 well plate reader. This is a considerable benefit to any region or country that wants to adopt antibody testing in the fight against COVID-19.

What enables the SeroKlir ELISA kit to achieve 97.8% sensitivity and 99.6% specificity for detecting SARS-CoV-2 specific IgG antibodies?

The use of both a screening plate (RBD) and a confirmatory (Spike) plate enables SeroKlir to reach these extremely high levels of sensitivity.

Can you tell us a bit about how SeroKlir can be used in terms of mapping the kinetics of the antibody response to SARS-CoV-2, and the importance behind this?

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 the SARS-CoV-2 virus in vitro.

In addition to this, what role can this testing method play in terms of serosurveys aimed at determining the real attack rate and infection fatality rate in different human populations?

Nucleic acid tests that detect the SARS-CoV-2 RNA genome are now widely employed to diagnose COVID-19. There remains a great need for assays that measure antibody responses and determine seroconversion. Serological assays are not well suited to detect acute infections, but they do support a number of highly relevant applications. First, serological assays allow us to study the immune response(s) to SARS-CoV-2 in a qualitative and quantitative manner. Second, serosurveys are needed to determine the precise rate of infection in an affected area, which is an essential variable to accurately determine the infection fatality rate. Third, serological assays will allow for the identification of individuals who mounted strong antibody responses and who could serve as donors for the generation of convalescent serum/plasma therapeutics. Lastly, serological assays can help inform studies that aim to identify antibody responses that correlate with protection from SARS-CoV-2.

What are some of the real-world applications the Kantaro COVID-SeroKlir kit can be utilized in?

The Kantaro COVID-SeroKlir kit will be of critical importance to help define previous exposure to SARS-CoV-2 in populations, identify highly reactive human donors for convalescent plasma therapy, and investigate correlates of protection. EKF and Kantaro are working with clinicians to understand wider population responses to infection and vaccination. Additionally, we are looking at distinct clinical populations such as immunosuppressed patients (e.g. post-transplantation) to determine vaccine responses.


  1. Amanat et al. Nature Medicine 26 2033-1036 (2020)
  2. Wajnberg et al. Science 10.1126/science.abd7728 (2020).

Where can readers find more information?

About EKF

EKF Diagnostics Holdings plc, which includes the EKF Diagnostics, Stanbio Laboratory, and DiaSpect brands, specializes in the development, production, and worldwide distribution of point-of-care analyzers for use in the detection and management of diabetes and anemia, and also in sports and maternal medicine. EKF products are sold in more than 100 countries around the globe, through a network of specialist distributors.

About Gary Dowthwaite

Gary is Special Projects co-ordinator at EKF Diagnostics and is responsible for the SeroKlir ELISA kit as well as the company’s range of lactate and glucose measuring diagnostic tools.


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