Rapid diagnostic test for covid 19 may take around 10-20 minutes and are relatively simple to perform and interpret and therefore require limited test operator training. These slides illustrate the general concept of rapid test especially testing IgG and IgM antibodies against SARS-CoV-2 antigen .

1. Anup Muni Bajracharya

2. Introduction
 Coronaviruses are enveloped RNA viruses
 distributed broadly among humans, other mammals, and birds
and that cause respiratory, enteric, hepatic, and neurologic
diseases.
 Seven coronavirus species are known to cause human disease.
 Four viruses - 229E, OC43, NL63, and HKU1 - are prevalent and
typically cause common cold symptoms in immunocompetent
individuals.4
 The three other strains –
 severe acute respiratory syndrome coronavirus (SARS-CoV),
 Middle East respiratory syndrome coronavirus (MERS-CoV) and
 2019 Novel Coronavirus (COVID-19)

3. Introduction
 Rapid diagnostic test for COVID-19 is IgM-IgG
combined antibody test.
 Used to detect IgG and IgM antibodies of the novel
coronavirus in human serum, plasma or whole blood
in vitro.
 These proteins (Immunoglobulins) indicate that a
person’s immune system has responded to infection
with the COVID-19 virus.

4. Introduction
 COVID-19 antibodies can be produced by a host
immune system following exposure to SARS-CoV-2.
 IgG and IgM antibodies are among the antibody
isotypes produced by vertebrate immune systems.
 IgM is the first antibody which appears in response to
initial exposure to antigens such as SARS-CoV-2
proteins.
 IgM antibodies are the main antibodies involved in the
primary immune response whereas IgG antibodies are
involved in the secondary immune response.

5. Why rapid test?
 Recent studies suggest that a high percentage of patients
show no clinical symptoms of the virus, which makes
screening patients vitally important.
 The test can be used for rapid screening of carriers of the
virus that are symptomatic or asymptomatic.
 With faster and accurate results, it can guide treatment
decisions and further enhance public safety measures.
 This information helps experts to better understand how
the virus spreads through populations and develop
strategies to prevent and slow the epidemic.
 The test is ideally suited for hospitals, clinics and test
laboratories, and can also be effectively deployed in
businesses, schools, airports, seaports and train stations,
etc. Thus can be even used in the field and used by general,
no expertise required.

6. Principle

The COVID-19 IgG/IgM Rapid Test Cassette (Whole
Blood/Serum/Plasma) is a lateral flow immunochromatographic
assay.
 The test uses anti-human IgM antibody (test line IgM) , anti-
human IgG (test line IgG) and goat anti-rabbit IgG (control line
C) immobilised on a nitrocellulose strip.
 The burgundy colored conjugate pad contains colloidal gold
conjugated to recombinant COVID-19 antigens conjugated with
colloid gold (COVID-19 conjugates) and rabbit IgG-gold
conjugates.

7. Principle
 When a specimen followed by assay buffer is added to the sample well,
IgM &/or IgG antibodies if present, will bind to COVID-19 conjugates
making antigen antibodies complex.
 This complex migrates through nitrocellulose membrane by capillary
action.
 When the complex meets the line of the corresponding immobilized
antibody (anti-human IgM &/or anit-human IgG) the complex is
trapped forming a burgundy colored band which confirm a reactive test
result.
 Absence of a colored band in the test region indicates a non-reactive
test result.
 The test contains an internal control (C band) which should exhibit a
burgundy colored band of the immunocomplex goat anti rabbit
IgG/rabbit IgG-gold conjugate regardless of the color development on
any of the test bands.
 Otherwise, the test result is invalid and the specimen must be retested
with another device.

8. Protocol

12. Results Interpretation

13. Results Interpretation
 A colored band will appear in the top section of the
result window to show that the test is working
properly. That band is control line.
 A colored band will appear in the lower section of the
result window. These bands are test line of IgM/IgG
 Even if the control line is faint, or the test line is not
uniform, the test should be considered to be
performed properly and the test result should be
interpreted as a positive result.

14. Merits and Demerits
 Merits
 Instead of deep throat or nose swabs that are intrusive and
typically require hours or even days before the results are
known,
 rapid tests use blood samples and a small device that
measures antibody response to the virus within 10-15
minutes. (fast)
 Easy to use
 Demerits
 Rapid test kit results should not be used as the sole basis
for diagnosis or for confirmatory testing.
 The results need to be interpreted together with clinical
examination and confirmed with supplemental testing.

15. References
 https://highplustech.en.made-in-china.com/product/KvSQBChxMerF/China-
Covid-19-Igg-Igm-Antibody-Rapid-Test-Kit.html
 https://www.hospimedica.com/coronavirus/articles/294781129/biomedomics-
launches-covid-19-igm-igg-rapid-test-for-novel-coronavirus.html.
 https://www.asianscientist.com/2020/04/pharma/biolidics-rapid-test-kit-
covid/
 https://sugentech.com/products/products-view.php?ct=7&target=32