What COVID-19 Antibody Tests Can and Cannot Tell Us?
Serological screening of COVID-19 infection based on the antibody detection helps in multiple ways because it’s easy to handle and operator friendly since we use serum samples which is less complicated when compared to the respiratory track fluid samples for other type of tests.
In this COVID-19 pandemic situation, antibody test results are especially important for detecting previous infections in addition to the current infection. Antibody tests based on IgG antibody detection aid to provide results to individuals or healthcare providers to show whether someone was previously infected with SARS-CoV-2 and developed immunity. This will help in allaying the fear and anxiety of health care workers, office employees, corona warriors, etc. They are risk free to get back to work. Serological tests based on all classes of antibody (IgM, IgA and IgG) detection assays, if used in conjunction with other diagnostic tests like RTPCR or SARS CoV2 antigen detection assays, along with assessment of patient’s clinical history may be helpful as part of the testing algorithm to establish a diagnosis of COVID-19 and identify probable cases as part of early diagnosis and treatment. In addition, serological test results help to identify SARS CoV2 recovered individuals who mounted a strong immunological response to the virus and whose antibody isolates can be used to treat patients via convalescent plasma therapy. Sero-surveillance study based on the detection of Anti SARS CoV2 IgG antibody testing, can improve our understanding of disease transmission patterns, the scale of current pandemic conditions, the cumulative incidence of infection in the population and there-by provide useful public-health information.
Serological testing should not be used as a stand-alone test to diagnose someone with active SARS CoV2 infection. A negative result by serological method does not rule-out SARS CoV2 infection in the current situation because of the window period of infection. Further, a positive result in serological testing does not mean that the individual is immune to COVID-19 infection and free from re-infection. At present, even though the positive result provides evidence of prior infection with SARS-CoV-2, there is no assurance of protective immunity. There may be a fraction of opportunity that a positive result does not rule out that the person is no longer shedding virus or is no longer infectious.
In antibody screening assays, the specificity of the assay plays a major role and it should not have any cross reactivity to other strains of normal corona viruses which cause the common cold and circulate widely. If the serological assays lack higher specificity, they may lead to false positive results. Those people with false positive results may increase the risk of getting infection and pave way for continued transmission. Hence it is very important to select the assays which are having excellent specificity for the screening of COVID-19 infection in sero-surveillance.
Context to this recently Ortho Clinical Diagnostics has launched VITROS Anti SARS CoV2 Total antibody and VITROS Anti SARS CoV2 IgG antibody screening assays with excellent (100%) specificity and no cross-reactivity with other respiratory track viral infections.
