SARS-CoV-2 serology in MIS-C


Objectives. We aimed to measure SARS-CoV-2 serologic responses in children hospitalized with multisystem inflammatory syndrome (MIS-C) compared to COVID-19, Kawasaki Disease (KD) and hospitalized pediatric controls.

Methods. From March 17, 2020 – May 26, 2020, we prospectively identified hospitalized children at Children’s Healthcare of Atlanta with MIS-C (n=10), symptomatic COVID-19 (n=10), KD (n=5), and hospitalized controls (n=4). With IRB approval, we obtained prospective and residual blood samples from these children and measured SARS-CoV-2 spike receptor binding domain (RBD) IgM and IgG, full-length spike IgG, and nucleocapsid protein antibodies by quantitative ELISAs and SARS-CoV-2 neutralizing antibodies by live-virus focus reduction neutralization assays. We statistically compared the log-transformed antibody titers among groups and performed linear regression analyses.

Results. All children with MIS-C had high titers of SARS-CoV-2 RBD IgG antibodies, which correlated with full-length spike IgG antibodies (R2 =0.956, P<0.001), nucleocapsid protein antibodies (R2 =0.846,P<0.001), and neutralizing antibodies (R2 =0.667, P<0.001). Children with MIS-C had significantly higher SARS-CoV-2 RBD IgG antibody titers (geometric mean titer [GMT] 6800, 95% CI 3495-13231) than children with COVID-19 (GMT 626, 95% CI 251-1563, P<0.001), KD (GMT 124, 95% CI 91-170, P<0.001) and hospitalized controls (GMT 85, P<0.001). All children with MIS-C also had detectable RBD IgM antibodies, indicating recent SARS-CoV-2 infection. RBD IgG titers correlated with erythrocyte sedimentation rate (R2 =0.512, P<0.046) and with hospital (R2 =0.548, P=0.014) and ICU lengths of stay (R2 =0.590, P=0.010).

Conclusion. Quantitative SARS-CoV-2 serology may have a role in establishing the diagnosis of MIS-C, distinguishing it from similar clinical entities, and stratifying risk for adverse outcomes.

SOURCE: Pediatrics

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Fulgent (COVID-19) Antibody Testing

Test Description

The Fulgent COVID-19 IgM/IgG DR Test is a solid phase immunochromatographic assay for the rapid, qualitative, and differential detection of human IgG and IgM antibodies against SARS-Cov-2 from whole blood, plasma, or serum samples.

The presence of these antibodies is indicative of an adaptive immune response to COVID-19, indicating recent or prior infection. The test uses anti-human IgM and IgG antibodies immobilized on separate nitrocellulose membrane strips to capture and detect antibodies against COVID-19 antigens. IgM antibodies are produced during the early phase of infection (first few days), whereas IgG antibodies are typically detectable during the active, late, and recovery phase of infection (7-10 days post-infection). Fulgent’s Antibody Test screens for both markers to maximize the detection of antibodies against SARS-CoV-2.

* This test has not been cleared or approved by the FDA. Fulgent’s laboratory is regulated under CLIA and is qualified to perform high-complexity testing for investigational or research purposes. This test should not be used as a diagnostic test. Since systematic and technical factors can affect the accuracy of testing, the results of testing should always be interpreted in the context of clinical and familial data.


  • Whole blood, plasma, or serum sample
  • Test results will be reported as positive, negative, or indeterminate
  • The option to retest if indeterminate is available

Turnaround time

Results are typically available within 1-2 days of your sample being received by the lab.

Performance MeasureEstimate Performance
Sensitivity (PPA)97.1%
Specificity (NPA)87.5%

MORE INFO: Fulgent

Passive immunization


We review aspects of the antibody response to SARS-CoV-2, the causative agent of the COVID-19 pandemic. The topics we cover are relevant to immunotherapy with plasma from recovered patients, monoclonal antibodies against the viral S-protein, and soluble forms of the receptor for the virus, angiotensin converting enzyme 2. The development of vaccines against SARS-CoV-2, an essential public health tool, will also be informed by an understanding of the antibody response in infected patients. Although virus-neutralizing antibodies are likely to protect, antibodies could potentially trigger immunopathogenic events in SARS-CoV-2-infected patients or enhance infection. An awareness of these possibilities may benefit clinicians and the developers of antibody-based therapies and vaccines.

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