The body immune system produces antibodies — proteins that are critical for fighting and clearing out the virus.Introduction: SARS CoV 2 is an enveloped, single-stranded RNA virus of the family Coronaviridae, genus Beta coronaviruses.

SARS CoV 2 is transmitted person-to-person primarily via respiratory droplets, but also indirect transmission through contaminated surfaces is possible.

SARS CoV 2 can be isolated from respiratory samples obtained via naso/oropharyngeal swabs or from sputum. The virus accesses host cells via the angiotensin-converting enzyme 2 (ACE2), which is the most abundant in the lungs.

The incubation period for COVID 19 is thought to range from 2 14 days following exposure, with most cases showing symptoms approximately 4 5 days after exposure.
Definite COVID 19 diagnosis entails SARS CoV 2 detection by RT PCR method

Antibody to SARS CoV 2 is an immunoassay test for qualitative detection of antibodies (including IgG) to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS CoV 2).

Seroconversion or recovery is observed after a median of 10 13 days after symptom onset for IgM and 12 14 days for IgG and last for several months. Levels and chronological order of IgM and IgG antibody appearance are highly variable supporting detection of both antibodies simultaneously.

Antibody tests results indicate how many people had COVID-19 and recovered including those who didn’t have symptoms. This aids in determining who might have immunity. It is for sero-surveillance purpose and not for COVID-19 diagnosis.Primarily, this test will help you to determine the optimum ‘BACK to WORK’ strategy for your organisation.

The timing and type of antibody test affect accuracy so the test is generally done after 2 weeks of infection. Another benefit of accurate antibody testing is that people who’ve recovered from COVID-19 may be eligible to donate plasma, a part of their blood.

However, the WHO (World Health Organization) has cautioned against considering it as a passport to complete immunity. The chances of infection among people with antibodies in their system are under research and soon it will be clear whether developing antibody means permanent protection against Covid-19 infection.

Covid RT PCR Nasopharyngeal swab test is definite diagnosis for SARS CoV 2 infection.The FDA approved two types of tests for diagnosing COVID-19 — molecular and antigen.

• Molecular test- This test detects genetic material of the virus using a lab technique called polymerase chain reaction (PCR). Also called a PCR test, a health care worker collects fluid from a nasal or throat swab or from saliva. Molecular tests are considered very accurate when properly performed by a health care professional
• Antigen test- This newer COVID-19 test detects certain proteins that are part of the virus. Using a nasal or throat swab to get a fluid sample, antigen tests can produce results in minutes. Because these tests are faster and less expensive than molecular tests are, some experts consider antigen tests more practical to use for large numbers of people. A positive antigen test result is considered very accurate, but there’s an increased chance of false negative results — meaning it’s possible to be infected with the virus but have negative antigen test results. So antigen tests aren’t as sensitive as molecular tests are. Depending on the situation, the doctor may recommend a molecular test to confirm a negative antigen test result.

Antibody test helps to find recovery or seroconversion from the virus and done 2 weeks post symptoms.

• The timing and type of antibody test affects accuracy. so test ideally done after 2 weeks of infection
• Another benefit of accurate antibody testing is that people who’ve recovered from COVID-19 may be eligible to donate plasma, a part of their blood.
• Antibody tests results indicate how many people had COVID-19 and recovered, including those who didn’t have symptoms. This aids in determining who might have immunity. It can also help in contact tracing to assess who else is at risk of infection and how far the disease spread. All of this data will help improve strategies to curb the COVID-19 pandemic.
• But the World Health Organization cautions that there’s a lack of evidence on whether having antibodies means you’re protected against reinfection with COVID-19. The level of immunity and how long immunity lasts are not yet known

Detection of IgG antibodies for SARS-CoV-2 may be useful in the following situations:

• Serosurveys to understand the proportion of population exposed to infection with SARS-CoV-2 including asymptomatic individuals. Depending upon the level of seroprevalence of infection, appropriate public health interventions can be planned and implemented for prevention and control of the disease. Periodic serosurveys are useful to guide the policy makers.
• Survey in high risk or vulnerable populations (health care workers, frontline workers, immunocompromised individuals, individuals in containment zones etc) to know who has been infected in the past and has now recovered.

Specificity is 99.8 %.

Typically, in this pandemic period, most doctors only suggest a test to diagnose COVID-19 if you have symptoms or you’ve had exposure to someone with COVID-19. To get antibody testing, you have to be fully recovered from COVID-19. But in a limited number of communities, people who never had symptoms of COVID-19 are included in testing. Some have positive results, meaning they likely were infected by the COVID-19 virus at some time.Ideally any individual can go for the test and we can promote to general population

Simple blood test venous blood and done on fully automated analyser Roche ECLIA method. Results on same day

Interpretation:

• Reactive results mean Positive for anti SARS CoV 2 antibodies and possibility of seroconversion due to past exposure or presumed immunity
• Non-Reactive results Negative for anti SARS CoV 2 antibodies and possibility of no exposure to virus. Negative test result does not completely rule out the possibility of an infection with SARS CoV 2. Serum or plasma samples from the very early (pre-seroconversion) phase can yield negative findings. Therefore, this test cannot be used to diagnose an acute infection