The management of coronavirus outbreaks is at a critical point where there is a widespread need for accurate and fast testing. The backbone of coronavirus testing has been Polymerase Chain Reaction (PCR) testing but the present time demands urgent surveillance of the population at risk due to not presenting any symptoms. One of the ways to slow down the spread of coronavirus, reduce healthcare burden, and keep healthcare professionals safe is through testing and rapid antibody testing is one such way. Several rapid and instrument-free antibody testing kits are available commercially.
WHAT IS ANTIBODY RAPID TESTING?
Antibody testing also called serology testing is a blood test that determines whether a person got infected with coronavirus in the past or not. An antibody test does not look for the virus itself instead it detects antibodies produced against the coronavirus (1). In response to an infection, the human body produces proteins known as antibodies. The body takes almost one to three weeks to start producing antibodies (2) because of this an antibody test is not used to detect a current infection. A rapid antibody test produces the result in a duration of fifteen minutes (3).
An antibody test usually detects isotypes of antibodies namely IgG and IgM (4). After a person contracts a coronavirus infection, the antibodies specific antigen presents on the spike protein of the virus appear in the blood of the patient. First, the appearance of IgM antibodies takes place within a few days of infection that lasts for several weeks even post-infection. This is followed by the appearance of IgG antibodies. Currently, most of the rapid antibody tests for coronavirus heavily depend on the ability to capture IgG or IgM antibodies with the help of recombinant proteins of the receptor-binding domain (RBD), S1, S2 subunits, and nucleocapsid (N) protein of the spike protein of the coronavirus (5,6).
HOW DOES AN ANTIBODY RAPID TEST PERFORM?
A rapid antibody test for coronavirus is usually used at point-of-care. Since the antibody tests are serology tests, it involves drawing blood by pricking the finger. The rapid antibody test kits are accompanied by a capillary tube with the help of which an appropriate amount of blood is drawn. The fingertip is cleaned with an alcohol swab and pricked with the help of a sterilized lancet. In a horizontal position, the tip of the capillary tube is touched to the blood drop on the fingertip. Blood is drawn in the tube by the capillary action. The drawn blood is then applied to the sample well present on the test device. After that, a sample buffer is also added to the sample well. The results are produced within ten to fifteen minutes (7).
HOW DOES AN ANTIBODY RAPID TEST WORK?
The test device contains anti-human Igg and anti-human IgM antibodies on a nitrocellulose membrane in the form of two lines. The membrane also contains a control line. The recombinant antigen of coronavirus is present on the conjugated pad in conjunction with colloid gold. If IgG or IgM antibodies are present in the sample, they will bind with coronavirus conjugate resulting in the formation of an antigen-antibody complex. When this complex comes in contact with the immobilized antibody on the membrane, it becomes trapped forming a red line indicating a positive test result. In case a red line does not appear, it represents a negative test result (8).
BENEFITS OF ANTIBODY RAPID TEST
The rapid antibody tests for coronavirus are rapid and reliable testing offering several benefits discussed below.
- Rapid Screening:
The gold standard for coronavirus testing is the PCR test but it takes almost twenty-four hours to three days to produce a result. In the times where the need to contain the spread of the virus is an all-time high, rapid antibody tests produce a result in a maximum of thirty minutes (9). This also eliminates the need for follow-up for the results.
- Easy to Handle
The simplicity of rapid antibody test kits makes it easy to handle eliminating the need for qualified and trained staff to administer the test. Moreover, rapid antibody testing does not require any fancy equipment to operate (10).
- Lessen the Burden on Healthcare Sector
The burden on the infrastructure of healthcare can be relieved with the help of rapid antibody testing by making accurate and reliable testing in decentralized locations that complements the laboratory diagnostics and allows efficient screening. With the help of rapid antibody testing, mass screening is possible without over-burdening the laboratories and specialist staff. In combination with national and local policies, convenient and quick answers can be delivered to the patients that can help to transform their behaviors. This could help in containing the virus and optimizing the restriction strategies. Moreover, rapid antibody tests also help in avoiding the follow-up appointments between doctors and patients to discuss the results.
The antibody rapid test also offers the following benefits as well.
- The rapid antibody test kits make testing possible in areas where there is no availability of laboratory testing and also in the circumstances where there is no suitability to draw blood from a vein.
- The test requires a very small amount of blood that is 20 microliters.
- The test helps to identify the previous infection in asymptomatic individuals.
- In certain circumstances, the test helps to identify the period when the infection occurred since it is common knowledge that IgM antibodies appear before IgG antibodies and IgM antibodies disappear before the appearance of IgG antibodies.
- The rapid antibody test helps to identify individuals who can qualify as donors of convalescent plasma which is a blood product containing antibodies against coronavirus and used in the treatment of seriously ill coronavirus patients (10).
- The rapid antibody tests help in epidemiological studies to estimate case fatality rate and attack rate.
- It helps the healthcare workers to reduce their exposure to the virus through infected individuals.
- It also helps in the evaluation of effects produced by non-pharmacological interventions in a population and thereby aid in the process of policymaking (9).