CORONA (COVID-19) TESTS
COVID-19 is the name of the infection and illness caused by the new strain of coronavirus called SARS-CoV-2. One type of COVID-19 test detects the genetic material (RNA) of the virus in a sample from the respiratory tract. COVID-19 serology blood tests detect antibodies produced in response to the infection. COVID-19 antigen tests detect viral protein in respiratory samples, but these tests are not in widespread use yet.
A viral test tells you if you have a current infection while an antibody test might tell you if you had a past infection. An antibody test might not show if you have a current infection because it can take 1–3 weeks after infection for your body to make antibodies. Having antibodies to the virus that causes COVID-19 might provide protection from getting infected with the virus again. If it does, we do not know how much protection the antibodies might provide or how long this protection might last.
Different Types of COVID-19 Tests
Types of Coronavirus (COVID-19) Diagnostic Tests
Information for test
1. Molecular Test
2. Antigen Test
3. Antibody Test
Other name of test
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
Sample collection types
Nasal or throat swab (most tests) & Saliva (a few tests)
Nasal or throat swab
Finger stick or blood draw
Test results time/duration
Same day (same locations)
or up to a week
One hour or less
Same day (many locations) or 1-3 days
Is another test recommended?
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.
Final test result
Diagnoses active coronavirus infection
Diagnoses active coronavirus infection
Shows if you’ve been infected by coronavirus in the past
Test can’t do the followings:
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
There are two kinds of tests are generally available for coronavirus (COVID-19) at present:
A. Coronavirus Viral Tests/Diagnostic Tests
- Corona Molecular(RT-PCR) Test
- Corona Antigen (Proteins) Tes
B. Corona Antibody Test
A. Corona Viral Tests/Diagnostic Tests
A corona viral or diagnostic test can show if you have an active coronavirus infection and should take steps to quarantine or isolate yourself from others. There are two types of viral diagnostic tests which detect the virus:
1. Corona Molecular (RT-PCR) Test
Reverse transcription polymerase chain reaction (RT-PCR) Tests detect the virus’s genetic material whereas corona antigen tests detect specific proteins on the surface of the virus.
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:
(i) A doctor, pharmacist, or other health professional orders a COVID-19 test. All COVID-19 tests, including those used with a home collection kit, require a prescription or order from a health professional.
(ii) You or a health care professional use a specialized swab to collect mucus from your nose or throat.
(iii) You or a health care professional put the swab in a sterile container and seal it for transport to a lab.
(iv) 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.
(v) A lab technician mixes chemicals with the swab to extract the genetic material of any virus that may be on the swab.
(vi) 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.
(vii) 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.
The US Food and Drug Administration (FDA) continues to work with test developers to make more coronavirus tests available to more people in the future.
Molecular diagnostic tests that 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.
2. Coronavirus 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 (RT-PCR) test to confirm the result.
B. Coronavirus Antibody Tests
An antibody test looks for antibodies that are made by your immune system in response to a threat, such as a specific virus. Because antibodies can help fight infections. Thus coronavirus antibody test might tell you if you had a past infection. Antibodies can take several days or weeks to develop after you have a viral 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.
C. Some New Diagnostic Tests for Coronavirus
- 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.
- At-home collection tests, available only by prescription from a doctor, allow the patient to collect the sample at home and send it directly to the lab for analysis.
- 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 Uses of Coronavirus Tests
During a public health emergency like the COVID-19 pandemic there is an urgent need for products to diagnose, treat or prevent a medical threat. There are two ways a coronavirus test might be used for this emergency:
1. Emergency Use Authorization (EUA)
In certain types of emergencies, the government authorized agency of country such as FDA in US can issue an Emergency Use Authorization, or EUA, to provide more timely access to critical medical products that may help during the emergency when there are no adequate, approved, and available options. The EUA process is different than full approval or clearance because in some emergency situations we cannot wait for all of the evidence needed for full government authorized agency approval or clearance. Instead, the FDA evaluates the options very quickly using the evidence that is available, carefully balancing the risks and benefits of the product as we know them, in addition to evaluating other criteria. FDA has issued many EUAs for diagnostic tests and antibody tests.
To expand the nation’s COVID-19 testing capacity, the US Food and Drug Administration (FDA) also issued a policy guidance offering regulatory flexibility in certain circumstances. The policies in this guidance apply to commercial manufacturers and to laboratories certified under the Clinical Laboratory Improvement Amendments (CLIA) to perform high-complexity testing and who create laboratory-developed tests (LDTs) for coronavirus. In the guidance, the FDA outlines policies for test developers that offer certain types of COVID-19 tests before they receive an EUA for that test, under the circumstances described in the guidance. Under certain policies in the guidance, the test developers validate their test, give notice to FDA, and submit an EUA request within a specified timeframe.
2. State Authorization of LDTs
The FDA in USA is providing flexibility to states that want to authorize labs certified to conduct high-complexity testing in that state to develop and perform coronavirus testing. Under this policy, the state or territory takes responsibility for the safety and accuracy of COVID-19 testing by laboratories in its state/territory and the lab does not submit an EUA request to the FDA.
3. Coronavirus Testing in Your Community