Revista de Métodos de Diagnóstico Médico
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SARS-CoV-2 Antibody Test-Is It Reliable?

Razia Kausar

The immune system releases antibodies in response to the foreign particles or threat such as specific virus. To detect these antibodies a serological test or SARA-CoV-2 antibody test is under preference now days. This serological testing is proved beneficial to know the history of infection in an individual, in screening the disease stage and in development & improvement of vaccine. The serological/antibody testing possessing high sensitivity implies that the assay will give less false results that consequently help in identification of previously infected patients.

In antibody testing, body’s immune response to past or active infection from CoV-2 virus is examined while in PCR based testing, SARS-CoV-2 infection is directly identified by the presence of genetic material (RNA). Both types, specific as well as sensitive test development is critical.

It has been observed that antibody response varies with disease severity in different patient samples.  Various research studies shows that patients with severe Covid-19 produce relatively high number of antibodies in comparison to those with mild infection. This is the reason that Positive Percent Agreement – PPA or sensitivity is higher in the individuals having more severe symptoms because of Covid-19 infection.

A qualitative IVD test is recently developed to detect antibodies produced in response to SARS-CoV-2. This immunoassay comprises of two protein fragments. One fragment is SARS-CoV-2 specific protein and the another one is subunit of NanoBiT (NanoLuc Binary Technology) Luciferase. If antibodies (to SARS-CoV-2) are present in the serum or plasma then an active luminescent enzyme is formed because the protein fragments are drawn into close proximity by the antibodies. In this immunoassay type, the binding interactions occur in homogeneous solution unlike to ELISA in which antibody interaction take place in heterogeneous solution. Apart from this, the IVD test is fast and simple also. Customary ELISA techniques include numerous hatching and wash steps regularly prompting conflicting information, incorporate different neutralizer and identification steps frequently diminishing explicitness and expanding foundation commotion, and can take hours to get results.

The IVD SARS-CoV-2 immunoassay takes out the requirement for all washes, lessening the convention to only a couple straightforward advances. This implies less active time, permitting a lab to travel through the work process quicker and go from test to bring about not exactly 60 minutes. The work process doesn't need particular plates or an interest in enormous lab gear, rather a brilliant proficient microplate per user is required. Likewise, examination can be effortlessly computerized on most significant fluid overseers to oblige testing of huge example sets.

The main limitation of antibody tests for SARS-CoV-2 is that there is no exact idea about how long the antibodies last in the body or if the presence of antibodies in an individual is immune to virus in future or not.

The SARS-CoV-2 immunoassay distinguishes human antibodies against the Receptor Binding Domain (RBD) antigen inside the S1 subunit of the SARS-CoV-2 Spike (S) protein, not at all like numerous neutralizer tests available that recognize antibodies against the Nucleocapsid (N) protein. Exploration has shown that the Spike (S) protein may offer preferred affectability over the Nucleocapsid (N) protein for estimating SARS-CoV-2-explicit antibodies. The numerous specialists have exhibited that antibodies created against the Spike (S) protein, numerous explicitly delivered against the RBD space, are fit for viral balance and are focused in treatment and immunization advancement endeavours.

For commonness testing and screening, immune response tests can be utilized to distinguish people who were not hospitalized and might not have had a known SARS-CoV-2 contamination. Also, the clinical presentation of several examinations shows that antibody response can increase with manifestation seriousness.