The new coronavirus (SARS-CoV-2), which emerged in December 2019, had spread rapidly around the world. Medical systems faced serious clinical and public health management challenges. Diagnostic tests with high reliability, sensitivity and specificity are required to identify the appropriate responses to the epidemic and manage the disease. 

Testing to determine who encounters the SARS-CoV-2 virus has become one of the most fundamental elements of slowing down global pandemic. Testing much of the society could be the key to returning to normal life. "You cannot fight a fire blindfolded. And we cannot stop this pandemic if we don't know who is infected. We have a simple message for all countries; test, test, test." WHO Director-General Dr.Tedros Adhanom Ghebreyesus said in a press conference in Geneva. (General's opening remarks at the media briefing on COVID-19 - March 16th, 2020)

Coronavirus (SARS-CoV-2), which is the cause of severe Acute Respiratory Syndrome, is highly contagious and can result in comorbidity (presence of one or more additional diseases often co-occurring with a primary disease) – other Immunosuppressive conditions, especially Cardiovascular diseases, Diabetes Mellitus, Hypertension, Cancer, Chronic lung diseases – it may result in significant rate (5%) of mortality (crude death rate) in susceptible individuals. Acute symptoms and signs of infection such as fever, cough, fatigue, muscle pain and difficulty breathing are not highly specific to the SARS-CoV-2. About 20% of cases consist pneumonia, i.e. severe disease, while 80% of cases have mild symptoms or asymptomatic (non-findings) transmissions. Due to these characteristics of the disease, serological tests are very crucial in identifying asymptomatic silent infections, evaluating the patient's immune response, better predicting the progression of the disease, and understanding the forms of transmission of SARS-CoV-2. Serological tests also play a major role in terminating isolation procedures and identifying potential candidates for donation of convalescent plasma to provide plasma therapy to COVID-19 patients.

Both the FDA (American Food and Drug Administration) and the CDC (American Center for Disease Prevention and Control) emphasize the importance of serological tests for the detection of previous infections in asymptomatic individuals and patients presenting with late complications, and the importance of identifying individuals who has immune response to SARS-CoV-2.

There are two testing categories used in laboratories for SARS-CoV-2 detection:
- Tests that detect the virus itself (viral ribonucleic acid [RNA]) and
- Tests that measure the host's immune response to the virus (serological antibodies).

(Antibody: Molecules in the structure of glycoprotein developed by the immune system of organisms against organic structures that do not belong to their organisms. These molecules provide protection by early warning the organism against harmful effects that foreign molecules may cause. Immunoglobulins are classified in such as IgG, IgM etc.)

Nucleic acid amplification tests for viral RNA: Detection of the virus is usually achieved by detecting viral RNA through nucleic acid amplification using a polymerase chain reaction (PCR). The most commonly tested specimen types are nasopharyngeal swabs (nose) (more sensitive) and Oropharyngeal (throat) swabs. These tests are the gold standard for diagnosis during the acute phase of disease.

Antibody detection through serology: Antibodies are the proteins that help the immune system to identify and eliminate the threats. Once they are produced, they help to protect the body from the future infections caused by the same threat.  Serological tests detect proteins that are created in response to the coronavirus SARS-CoV-2 virus. There are serological tests that detect SARS-CoV-2 IgM, IgG or total antibodies in the blood.

Sensitivity and Specificity in Total Antibody Test against SARS-Cov2:

The development of the antibody response to infection depends on the host and takes time. Studies on SARS-CoV-2 pandemic show that most patients form antibodies within an average of 7-11 days after exposure to the virus, although some patients may develop antibodies sooner. Antibodies were observed for IgM in 5 days after the onset of symptom, and for IgG within a period of 5-7 days.

Serological tests can help to answer some key questions about coronavirus SARS-CoV-2 and define preventive strategies:
- Determining how many people encounter the virus in society,
- Detecting people who spread the disease without knowing it,
- In the evaluation of the effectiveness of measures taken to slow the spread of the disease,
- Determining the immune levels of infected employees, determining the time to return safe to work.

Serological tests can show who is carrying antibodies, even if the virus is no longer present in patients recovering from Covid-19 or able to carry the virus without notice. Identifying who has immune is important to determine who can safely return to work.