COVID-19 Virus Disease
There has been an outbreak of respiratory disease caused by a novel coronavirus that was first detected in China and which then spread to several locations internationally, including in the United States. The virus named Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), also known as “the COVID-19 virus”, causes the Coronavirus Disease (COVID-19). The WHO declared COVID-19 disease to be a pandemic in early March. Reported illnesses have ranged from very mild (including some with no reported symptoms) in the majority of the cases (80%) to severe in 20% cases, including illness resulting in death (in 1-4% cases).
There is no single ‘Gold Standard’ for the diagnosis of COVID-19 infection. The different diagnostic methodologies provide different information regarding COVID-19 infection and a complete clinical picture is made possible by using information provided by all testing methodologies.
Molecular Testing for COVID-19
COVID-19 disease diagnosis can be made in the viremia phase of the disease (during incubation period and first week of the disease since onset of symptoms) by detecting the virus nucleic acid using the RT-PCR. The RT-PCR test is a molecular-based test that supports diagnosis of an acute infection due to COVID-19 virus to inform patient care decisions and infection control actions to prevent spread of the disease. Generally, the RT-PCR test is performed using a nasopharyngeal swab.
Serological Testing for COVID-19
In the first week after the onset of symptoms and viremia, IgM antibodies appear in the blood as the initial immune response to the primary COVID-19 virus infection. These IgM antibodies become undetectable subsequently, therefore, the presence of IgM antibodies suggests a recent COVID-19 infection. IgG antibodies appear in the blood after the first week of the disease and IgG antibody titers remain elevated as immunological memory, therefore, the presence of IgG antibodies suggest a non-recent (past) COVID-19 virus infection. The simultaneous detection of IgM and IgG antibodies in blood can be useful for the presumptive differentiation between recent and past infection.
Rapcov™ COVID-19 Rapid Test is a serological test for the qualitative detection of IgG or IgM antibodies to the COVID-19 virus in human whole blood fingerstick samples
Specific Public Health and Medical Uses of Serological Tests
There exists a great need for laboratory assays that measure antibody responses. While serological assays are not well suited to detect acute infections, they support a number of highly relevant public health and medical applications.
- From a community perspective to limit the spread of infection, the Rapcov™ test may help in the following practical ways:
- Presence of IgM antibodies on Rapcov™ test may suggest a recent infection and such a result will support advice of social distancing in order to limit the spread of virus, and an immediate referral for molecular testing (Nasopharyngeal swab RT-PCR to detect viral nucleic acid) to confirm COVID-19 virus infection.
- Presence of IgG antibodies on Rapcov™ test may suggest a non-recent (past) infection and that neutralizing antibodies against the COVID-19 virus may be present in the blood. This may be good result. Presence of COVID-19 virus neutralizing IgG antibodies may suggest that the individual is immune from reinfection with COVID-19 virus. However, there is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection. Organizations such as the WHO continue to review the evidence on antibody responses to COVID-19 infection. Most of these studies show that people who have recovered from infection have antibodies to the virus. However, some of these people have very low levels of neutralizing antibodies in their blood, suggesting that cellular immunity may also be critical for recovery. As of 24 April 2020, no study has evaluated whether the presence of antibodies to COVID-19 virus confers immunity to subsequent infection by this virus in humans.
Link to article “Immunity passports” in the context of COVID-19 →
- In cases where nucleic acid amplification assays (RT-PCR) are negative and there is a strong epidemiological link to COVID-19 infection, serology tests (in the acute and convalescent phase) may support diagnosis of COVID-19 disease.
- Serosurveys are needed to determine the precise rate of infection in an affected area, which is an essential variable to accurately determine the infection fatality rate. Serological surveys can aid investigation of an ongoing outbreak and retrospective assessment of the attack rate or extent of an outbreak.
- From a medical decision-making perspective the information regarding presence of IgG or IgM antibodies in the blood may help save lives in the following ways:
- It may help medical decision making in the treatment of acutely ill hospitalized patients who have CT scan and other clinical findings consistent with COVID-19 disease, but a negative RT-PCR result. In these patients Rapcov™ test may provide information regarding presence of IgG or IgM antibodies to support a diagnosis of COVID-19 infection and facilitate appropriate medical treatments. There is no single ‘Gold Standard’ for the diagnosis of COVID-19 infection. The different diagnostic methodologies provide different information regarding COVID-19 infection and a complete clinical picture is made possible by using information provided by all testing methodologies.
- Currently there are no specific anti-viral treatments for COVID-19 disease. The Rapcov™ test administered in the communities can identify individuals who mounted strong IgG antibody responses and who could serve as donors for the generation of convalescent serum therapeutics. This serum can be administered for prophylaxis and treatment of COVID-19 infection to save lives.