COVID-19 Antibody (IgM and IgG)

Name of the Test: COVID-19 Antibody (IgM and IgG)
Test code: #201
Alias Names: Coronavirus antibody, SARS-CoV-2 antibody, 2019 Novel Coronavirus antibody

CoronaVirusImage
Pan Laboratories

Clinical Applications:

The 2019 Novel Coronavirus (COVID-19) is a single stranded RNA virus of Coronavirus family. The genetic sequences of COVID-19 have similarities to SARS-CoV and bat coronaviruses1. Coronaviruses cause respiratory infections in humans. Human to human transmission of Coronaviruses is primarily thought to occur among close contacts via respiratory droplets generated by sneezing and coughing. Coronaviruses are composed of several proteins2 including spike(S), envelope(E), membrane (M) and nucleocapsid(N).

The immune response to infection results in the production of antibodies including IgM and IgG. Zhao et.al.,3 described the antibody response in patients with COVID-19. Based on their follow-up of 173 patients with COVID-19 in China, IgM and IgG antibodies occurred in 94.3% and 79.8%, 15 days following onset. Seroconversion sequentially appeared for IgM, and then IgG, with a median time of 12 and 14 days respectively. Combining RNA and antibody detection significantly improved the sensitivity of diagnosis of COVID-19 in patients4. The National Health Commission of the Peoples Republic of China states that IgM antibodies begin to show after 3-5 days of onset of COVID-19. Serum samples from RT-PCR confirmed positive patients (n=20) were positive for IgG antibodies after two weeks of the onset of disease.

Studies are required to determine whether:

  • Antibody testing could supplement RT-PCR assays in the diagnosis of COVID-19
  • Infected individuals with minor or no symptoms have antibodies to COVID-19
  • The presence of antibodies in infected individuals prevent the recurrence of the COVID-19
  • The presence of such antibodies would justify the screening of health care workers to identify those who are already immune and can thus be deployed to care for infected patients5
  • The immune plasma from infected individuals could be potentially used in treatment or as prophylaxis?5

Methods:

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Antibodies to Human COVID-19 are measured by a qualitative ELISA method using HRP (Horse Radish Peroxidase) based system. For IgG antibody, microtiter wells coated with antigen (nucleocapsid protein) are used to bind Anti-COVID -19 IgG from patient serum/plasma. The bound IgG is measured using goat anti-human IgG- HRP. For IgM antibody, microtiter wells coated with anti-human IgM antibody are used to capture IgM antibody from serum/plasma, and the bound antibodies are detected with COVID-19 antigen-HRP. The color developed by the reaction of HRP and TMB is read at 450 nm.

Specimen requirements:

Specimen requirements: 1.0 ml of Serum or Plasma (0.3 ml minimum)

Shipping Requirements: Ship frozen in dry ice or refrigerated in ice packs

Turnaround time: 1 day

Reports:  Reported as antibody detected, not detected or equivocal (borderline)

References:

  1. Zhou, P., Yang, X- L, Wang X.G. et al (2020) A pneumonia out break associated with a new coronavirus of probable bat origin. Nature doi: 10: 1038/s41586-020-2101-7.
  2. Li, F.,Li, W., Farzan, M.and Harrison, S.( 2005) Structure of SARS coronavirus spike receptor-binding domain complexed with its receptor. Doi 10:2210/pdb2ajf/pdb.
  3. Zhao J, Yuan Q, Wang H, et al (2020) Antibody responses of SARS-CoV-2 in patients of novel coronavirus disease 2019. med/Rxiv preprint.        https://www.medrxiv.org/content/10.1101/2020.03.02.20030189v1.full.pdf .
  4. Haveri A, Smura T, Kuivanen S, et al (2020) Serological and molecular findings during SARS-CoV-2 infection: the first case study in Finland, January to February 2020.
    Eurosurveillance 2020.
  1. Amanat F, Nguyen T, Chromikova V, et al (2020) A serological assay to detect SARS- coV-2 seroconversion in humans. https://sciencespeaksblog.org/2020/02/12/immune-survivors-of-covid-19-protective-antibody-for-treatment-and-prophylaxis/