Explained: How To Know The Correctness of COVID-19 Tests

September 6, 2020

New Delhi (ABC Live India): Correctness of COVID-19 Tests :The Media reports are gripped with news of rising numbers of COVID-19 cases in India, as on the date, the National COVID-19 cases load of India has been reached to 40,23,179.

Some of the media reports suggested that the false positive COVID-19 test reports is one the reason behind sudden rise in the of COVID-19 positive cases in India.

ABC Research Team tried to find the true facts on false positive COVID-19 Test reports and Reports as under;

To know this one should understand how COVID-19 tests are conducted, and when a person is declared as positive COVID-19.

Currently there are two types of diagnostic COVID-19 tests are available for detecting Coronavirus in a person;

Molecular Test
Antigen Test

The Molecular Test like RT-PCR tests, we can detect whether virus’s genetic material is present in human body.

The Antigen Test looks for antibodies that are made by your immune system in response to a threat, such as a specific virus.

Antibodies can help fight infections. Antibodies can take several days or weeks to develop after you have an infection and may stay in your blood for several weeks or more after recovery. Because of this, antibody tests should not be used to diagnose an active Coronavirus infection.

At this time researchers do not know if the presence of antibodies means that you are immune to the Coronavirus in the future.

Molecular Tests

Many companies and labs have developed tests to diagnose COVID-19 based on detection of the virus’s genetic material in a sample from the patient’s nose or throat. These steps may change as new technology becomes available, but currently the typical steps in molecular testing are:

A health care professional use a specialized swab to collect mucus from your nose or throat and put the swab in a sterile container and seal it for transport to a lab.
During the shipping process, most molecular test swabs must be kept within a certain temperature range so that the test will be accurate. The sample must arrive at the lab within 72 hours.
A lab technician mixes chemicals with the swab to extract the genetic material of any virus that may be on the swab.
The lab technician uses special chemicals, called primers and probes, and a high-tech machine to conduct several controlled heating and cooling cycles to convert the virus’s RNA into DNA, and then make millions of copies of the DNA. Some tests use only one warming cycle to make copies of the DNA.
When DNA binds to specific probes, a special type of light is produced that can be seen by the machine and the test shows a “positive” result for infection with SARS-CoV-2, the virus that causes COVID-19.

Molecular diagnostic tests detect the genetic material of the virus are commonly used for diagnosing COVID-19 or active Coronavirus infection. But no test is 100% accurate all of the time. Some things that may affect the test’s accuracy include:

You may have the virus, but the swab might not collect it from your nose or throat.
The swab or mucus sample may be accidentally contaminated by the virus during collection or analysis.
The nasal or throat swab may not be kept at the correct temperature before it can be analyzed.
The chemicals used to extract the virus genetic material and make copies of the virus DNA may not work correctly.

Antigen Tests

Antigen tests usually provide results diagnosing an active Coronavirus infection faster than molecular tests, but antigen tests have a higher chance of missing an active infection. If an antigen test shows a negative result indicating that you do not have an active Coronavirus infection, your health care provider may order a molecular test to confirm the result.

Antibody (Serology) Tests

Antibody tests may provide quick results, but should not be used to diagnose an active infection. Antibody tests only detect antibodies the immune system develops in response to the virus, not the virus itself. It can take days to several weeks to develop enough antibodies to be detected in a test.

Apart from Above There are some new diagnostic tests available with alternative methods and benefits.

Rapid, point-of-care diagnostic tests use a mucus sample from the nose or throat but can be analyzed at the doctor’s office or clinic where the sample is collected and results may be available in minutes. These may be molecular or antigen tests.

Saliva tests allow a patient to spit into a tube rather than get their nose or throat swabbed. Saliva tests may be more comfortable for some people and may be safer for health care workers who can be farther away during the sample collection.

Different Types of Coronavirus Tests

	Molecular Test	Antigen Test	Antibody Test
Also known as…	Diagnostic test, viral test, molecular test, nucleic acid amplification test (NAAT), RT-PCR test, LAMP test	Rapid diagnostic test (Some molecular tests are also rapid tests.)	Serological test, serology, blood test, serology test
How the sample is taken	Nasal or throat swab (most tests)Saliva (a few tests)	Nasal or throat swab	Finger stick or blood draw
How long it takes to get results	Same day (some locations) or up to a Week	One hour or less	Same day (many locations) or 1-3 day
Is another test needed?	This test is typically highly accurate and usually does not need to be repeated.	Positive results are usually highly accurate but negative results may need to be confirmed with a molecular test.	Sometimes a second antibody test is needed for accurate results.
What it shows	Diagnoses active Coronavirus infection	Diagnoses active Coronavirus infection	Shows if you’ve been infected by Coronavirus in the past
What it can’t do	Show if you ever had COVID-19 or were infected with the Coronavirus in the past	Definitively rule out active Coronavirus infection. Antigen tests are more likely to miss an active Coronavirus infection compared to molecular tests. Your health care provider may order a molecular test if your antigen test shows a negative result but you have symptoms of COVID-19.	Diagnose active Coronavirus infection at the time of the test or show that you do not have COVID-19

ABC Research

As Per ICMR and the Ministry of Health and Family Welfare statistics till March 31, 2020, India was able to conduct only 42,788 COVID-19 tests, and as on date this number reached 4,77,38,491 in five months.

There is no data of COVID-19 tests available in public domain through which one can confirm the exact number of COVID-19 tests conducted in India as per above mentioned three types of COVID-19 Tests.

The Ministry of Health and Family Welfare on 05/09/2020 stated in its press release that a total of 4,77, 38,491 tests have been done so far across the country, and there are now 1647 testing laboratories operational which cover all States/UTs.

Conclusion: The Molecular Test, like RT-PCR is considered as highly accurate and usually does not need to be repeated, whereas Antigen Test if comes positive is usually highly accurate but negative results may need to be confirmed with a molecular test. Also in case of Antibody Test a second antibody test is needed for accurate results.

For Laymen, if your blood sample is taken from finger and result takes 1-3 days, then it is an Antibody Test for detecting if you’ve been infected by Coronavirus in the past, thus cannot able to detect active Virus.

In case of Antigen Test your sample is taken from Nasal or throat and test result comes in one hour or less, and it can detect active Coronavirus in your body but if your report comes negative, then Molecular Test like RT-PCR is recommended as this test can missing active virus.

If your sample is taken from Nasal, throat swab or Saliva, and results come in 1-7 days, then it should be Molecular Test like RT-PCR, and it is a highest accurate COVID-19 test available, and only fails if samples are not taken properly.