Types of  tests for COVID-19
The test to diagnose active infection includes molecular test/real-time polymerase chain reaction (RT-PCR) test/nucleic acid amplification test (NAAT) test and Rapid antigen test

COVID-19 is a respiratory disease caused by a novel virus called SARS-CoV-2. Most people infected with COVID-19 are asymptomatic (do not exhibit any symptoms). A few may have mild flu-like symptoms such as fever, dry cough and fatigue, sore throat, headache, body pain, and loss of smell and taste. In a small group of people, COVID-19 may cause respiratory distress presenting as difficulty in breathing, grunting, or noisy breathing (wheezing). Severe COVID-19 infection is associated with a high fatality rate.

Seeking early care if you have any respiratory symptoms and getting promptly tested will help you getting timely treatment and avoiding the development of complications.

Who should get tested?

The current Centers for Disease Control and Prevention (CDC) health guidelines for getting the tests done are as follows:

  • All individuals who exhibit the symptoms of COVID-19 must get tested after consulting their healthcare provider.
  • Individuals who were in close contact with a confirmed COVID-19 case (within 6 feet of an infected person for a total of 15 minutes or more over a 24-hour period) must get tested. The contact is the period considered within a period starting from two days before the illness onset (or, for asymptomatic patients, two days prior to testing specimen collection) until the time the patient is isolated.
  • Asymptomatic screening may be mandated by a health authority if you have traveled to an area with a high prevalence of patients with COVID-19 in the last 14 days or if you are undergoing any medical procedure.

What is the difference between the types of tests available for COVID-19?

Getting tested for COVID-19 can identify you as a positive or negative patient of the disease. Remember no test is 100% accurate. Different methods of testing have been launched to trace COVID-19 infection. These are as follows:

  • The test to diagnose active infection:
COVID-19 test to diagnose active infection
Sr. No.RT-PCR test/NAAT testRapid antigen test
1.It detects the presence of the viral particle (viral ribonucleic acid [RNA]).It detects a specific protein in the body that triggers an immune response to COVID-19 infection.
2.Results are available within one to seven days depending on your locality.Results are rapid and may be obtained in 1-24 hours.
3.

It is the best test available to confirm COVID-19 infection. The test is accurate around 60-95% of the time when properly conducted.

Compared with the NAAT test, this test has low sensitivity (around 56%). This means that there is more risk of missing an actively infected person with this test.

4.A nasal swab (from the nares) or nasopharyngeal swab (from the back of the throat) is collected for testing.A nasal or nasopharyngeal swab is collected for testing.
  • Tests to diagnose the past COVID-19 infection: A level of serum IgG antibodies for SARS-CoV-2 is measured for detecting any past infection.
    • The detection rate for SARS-CoV-2–IgG was 30% in the first week of infection,
    • 66% in the second week, and
    • 88% in the third week.
  • SARS-CoV-2 antibody test
    • Is done through blood or finger prick.
    • Should not be used for detecting active infection.
    • Reports may take one to three days to come.
    • Detects the body’s response to COVID-19 infection.

A positive antibody testing does not mean that you are immune to COVID-19 in the future.

Testing kits for COVID-19:

The following test kits are available in the market for sample collection. Most of the testing kits use the RT-PCR method to diagnose the virus.

  • Rapid, point-of-care diagnostic tests use a mucus sample from your nose or throat. This test is done at the doctor’s clinic where the sample is collected, and the results are available in minutes. These tests may be molecular- or antigen-based.
  • Combination tests are used for the detection of flu and coronavirus at the same time. Some can test for many different types of respiratory viruses, including SARS-CoV-2.
  • Saliva tests allow a patient to spit into a tube rather than get use their nose or throat swabs. Some people may prefer the saliva test to swabs. These are also safer for healthcare workers while sampling collection.
  • At-home collection tests, available only by prescription from a doctor, allow the patient to collect the sample from the back of the throat and send it directly to the lab

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Medically Reviewed on 12/1/2020
References
References:

1. https://www.uptodate.com/contents/coronavirus-disease-2019-covid-19-diagnosis?

2. https://www.who.int/emergencies/diseases/novel-coronavirus-2019/question-and-answers-hub/q-a-detail/coronavirus-disease-covid-19

3. https://www.fda.gov/consumers/consumer-updates/coronavirus-disease-2019-testing-basics#:~:text=Different%20Types%20of%20Coronavirus%20Tests&text=Negative%20results%20may%20need%20to,is%20needed%20for%20accurate%20results.&text=Antigen%20tests%20are%20more%20likely,infection%20compared%20to%20molecular%20tests. 4. https://www.cdc.gov/coronavirus/2019-ncov/php/open-america/testing.html