COVID-19 Testing Explained: Types, Accuracy, and What to Expect

COVID-19 vaccination might be the best way to lower the risk. With the rise of new infections of COVID-19, COVID-19 testing is the best way to detect and treat those new strains of the virus. Learn different types of COVID-19 testing in this article.

Types of tests

There is major 3 types of tests that are used for COVID-19 testing:

  1. Molecular tests.
  2. Lateral flow tests (LFTs)
  3. Antigen tests.
  4. Molecular tests:

These tests are the most accurate tests to detect the virus that causes COVID-19. It includes polymerase chain reaction (PCR) and other nucleic acid amplification tests (NAATs) which detect genetic material called the RNA of the virus. These tests can detect the virus even when you don’t have any symptoms and the virus is in its earliest stages. So, if you get a positive PCR or other molecular amplification test result means you are infected with COVID-19.

PCR tests are considered the “gold standard” of COVID testing because they are the most accurate. It can detect the virus strain of SARS-CoV-2, the virus that causes COVID, by directly screening the presence of viral RNA, even before the body forms antibodies or symptoms of the disease. This means PCR tests can tell if someone is infected with the virus or in the early stages of the illness.

Doctors will take a DNA sample from mucus or saliva to send to the lab for testing. Results can take up to 3 days. These tests are highly sensitive and more reliable than other tests which allow people to follow treatment guidelines to manage their condition and prevent the spread.

However, due to its sensitivity, it sometimes detects dead, deactivated viruses present in the body of someone who recovered from COVID-19. So, people who recovered don’t need to worry about being contagious and virus symptoms.

 2. Lateral flow tests (LFTs):

These tests are similar to PCR tests because both can pick up the active COVID-19 infection rather than antibodies of the disease. During this test, a nasopharyngeal sample is taken and put on a small absorbent pad, which is drawn along the pad via a capillary line to a strip coated in antibodies to bind the virus proteins. If viral proteins are present, then it shows a colored line on the test which indicates infection.

The major benefit of this test over PCRs is that you don’t need to send it to the lab to confirm your results. Instead, you can check results within 15 to 30 minutes. However, this speeded-up process of getting results can lack accuracy.

A review of 64 studies from Europe and the US showed that there is a wide gap in accuracy between different brands of LFT. It also found that these tests are far better at identifying COVID-19 in people who had symptoms than those who didn’t. LFT sensitivity works well in symptomatic people ranging from 34% to 88% with an average accuracy of 72%. However, in people without symptoms, it struggles and gives an average accuracy of 58% of those who were infected.

So, LFT use is recommended for people who have symptoms and want to check if they are infected or not, at home quickly.

3. Antigen tests:

Antigen tests, also known as rapid tests, look for specific proteins on the surface of the virus and tell whether you have an active COVID-19 infection or not. In comparison to PCR tests, it produces quick results usually within 30 minutes. These tests are recommended for at-home tests, where you collect your sample on your own and get results within minutes. This test is done with a nasal swab sample.

However, the problem with antigen tests is that their positive results are quite accurate, but this is not the case with negative test results. These tests are not as sensitive as molecular and lateral flow tests, no matter where they are performed, whether at home, a clinic, or a pharmacy. This means your negative test result is false and you’re infected with COVID-19, especially if you don’t have symptoms.

That’s why the CDC and FDA (Food and Drug Administration) recommend serial testing, which means taking more than one antigen test if your first test is negative. If you have COVID-19 symptoms and get a negative result, you should need to test again in 48 hours (about 2 days). If you don’t have symptoms but spend time with someone who is infected, then you may need a third antigen test 48 hours (about 2 days) after your second test. If that is negative, then take a single PCR test to confirm your antigen test result.

Types of samples

To diagnose COVID-19 infection, doctors use these types of samples for testing, including:

1.Swab samples: The doctor collects the testing sample from your nose or throat. It includes several types including:

  • Anterior Nares: A sample is taken from inside the nostrils of your nose.
  • Mid-turbinate: A sample is taken further up from inside the nose.
  • Nasopharyngeal: A sample is taken deep inside the nose or from reaching the back of the throat.
  • Oropharyngeal: A sample is taken from the middle part of your throat (pharynx) beyond the mouth.

2. Saliva samples: These samples are collected from your spit into a tube rather than from your nose or throat swab.

3. Blood samples: This sample is only used to check the antibodies, not to diagnose COVID-19. Venous blood samples are collected at the doctor’s office or clinic and some antibody tests also use blood samples from a finger stick.

Accuracy

When it comes to accuracy, molecular tests are the most accurate tests to diagnose COVID-19 infection. These tests can detect the earliest form of infection in the body even where antibodies or symptoms haven’t formed. However, results may take 3 days to come after testing.

Next is a lateral fluid test which is less accurate than molecular tests but detects viruses better than antigen tests. This test is highly sensitive to detect virus proteins in the body and produce quick results. But have less accuracy in people without symptoms. So, you can rely on the negative result of this test.

Lastly, antigen tests are less accurate when it comes to detecting the earliest form of the virus in the body. However, these tests are quite accurate in detecting the virus in people with symptoms or antibodies. That’s why it is recommended for people who want to take home tests or pharmacy tests to get quick results.

What to expect

For accuracy, getting the PCR test is the best option if you come in contact with someone who is infected. Depending on the lab your provider uses, you can expect your results within 24 to 72 hours (about 3 days). If your test is taken at home, then it may take 2 to 4 days for the results because those samples need to be tested thoroughly.

For quick accurate results, getting antibody tests is the best option, especially when you have COVID-19 symptoms. You can buy this test kit online or from a pharmacy. These tests produce fast results and are less expensive than PCR tests. However, it has a high chance of producing false-negative results. If an at-home antigen test is negative, then continue to wear masks in public places especially places where people are unvaccinated or high-risk. You can also take a PCR test to check your test results. If your at-home test result is positive, visit the doctor to follow lockdown guidelines and follow your treatment course.

There are 3 types of COVID-19 testing but the most common are PCR and antigen tests used to diagnose COVID infection. Both tests have their pros and cons. The best way to check COVID-19 infection is first to use an antigen test to get quick results and if negative and you still feel worried. Then take a PCR test to get accurate results after 3 days. Until then, take all necessary precautions to prevent the spread of disease to other people. If infected, visit the doctor for proper treatment and follow the necessary guidelines to stop its spread.

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