COVID-19 : Antigen Detection Test

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TOPIC: General Studies 2

• COVID-19  – Pandemic

General Studies 3:

• New technological development to fight COVID-19

In News: Indian Council of Medical Research, ICMR has recommended the use of rapid antigen test kits for diagnosis of COVID-19 in containment zones and healthcare settings in combination with the RT-PCR test. 

In India, the ICMR has allowed the use of antigen detection kits developed by the South Korean company S D Biosensor, which has a manufacturing unit in Manesar. The kit, commercially called Standard Q COVID-19 Ag detection kit, comes with a with an inbuilt Covid antigen test device, viral extraction tube with viral lysis buffer and sterile swab for sample collection.

Rapid Antigen Detection Test

• The rapid antigen detection test is to be used in specified settings, and kits from only one manufacturer have got approval.
• It is a test on swabbed nasal samples that detects antigens (foreign substances that induce an immune response in the body) that are found on or within the SARS-CoV-2 virus. 
• It is a point-of-care test, performed outside the conventional laboratory setting, and is used to quickly obtain a diagnostic result. 

How is rapid antigen detection test different from RT-PCR test?

RT-PCR is currently the gold standard frontline test for the diagnosis of Covid-19. Like RT-PCR, the rapid antigen detection test too seeks to detect the virus rather than the antibodies produced by the body. While the mechanism is different, the most significant difference between the two is time. 

• The RT-PCR test takes a minimum of 2-5 hours including the time taken for sample transportation. These specifications limit the widespread use of the RT-PCR test and also impedes quick augmentation of testing capacity in various containment zones and hospital settings.
• In a reliable rapid antigen detection test, the maximum duration for interpreting a positive or negative test is 30 minutes.

Where will the test be used?

The antigen test needs to be conducted at the site of sample collection in the healthcare setting. As of now, the kit will be used in containment zones or hotspots and healthcare settings. In both settings, the ICMR, has advised that the test will be performed onsite under strict medical supervision and maintaining the kit temperature between 2° and 30°C.

In containment zones, the test can be conducted on all symptomatic influenza-like illnesses. Asymptomatic direct and high-risk contacts with co-morbidities (lung disease, heart disease, liver disease, kidney disease, diabetes, neurological disorders, blood disorders) of a confirmed case are to be tested once between day 5 and day 10 of coming into contact.

In healthcare settings, it can be used in three categories. 

• First, in all persons presenting influenza-like symptoms in a healthcare setting and suspected of having Covid-19 infection
• Second, in asymptomatic patients who are hospitalised or seeking hospitalisation, in the following high-risk groups — those chemotherapy, immunosuppressed patients including those who are HIV positive, patients diagnosed with malignant disease, transplant patients, elderly patients (over age 65) with comorbidities
• Third, in asymptomatic patients undergoing aerosol-generating surgical/non-surgical interventions such as elective/emergency surgical procedures like neurosurgery, ENT surgery, dental procedures, and non-surgical interventions like bronchoscopy and dialysis.

Is the test a confirmatory one for diagnosis of Covid-19?

According to the ICMR guidelines, if the test shows a positive result, it should be considered as true positive, and does not need reconfirmation. However, those who test negative in the rapid antigen test should then be tested by RT-PCR to rule out infection.

Also, negative results from an antigen test may need to be confirmed with a PCR test prior to making treatment decisions or to prevent the possible spread of the virus due to a false negative.

Note:

The Indian Council of Medical Research (ICMR) 

• It is the apex body in India for the formulation, coordination and promotion of biomedical research.  

• The ICMR is funded by the Government of India through the Department of Health Research, Ministry of Health.  

Real-time reverse transcription polymerase chain reaction (RT-PCR)  

• It is a laboratory technique combining reverse transcription of RNA into DNA.  
• It detects the virus.  

Rapid antibody – based test 

• It uses blood.  
• It detects the body’s response to the virus.  
• A positive result tells that the body was exposed to the virus.  

Pooled sampling 

• It means testing samples from multiple patients with a single PCR test.  
• It has been used previously in the early stages of the HIV epidemic. 
• Such tests reduce the time, cost, and resources required.  
• It identifies infected people in a population and estimates the infection rate.  
• This allows medical experts to identify community clusters for targeted public health interventions.