Viral testing, often known as diagnostic tests, can detect the presence of SARS-CoV-2, the virus responsible for COVID-19. Two types of diagnostic testing exist: molecular and antigen.
If you have questions about which test is appropriate for you, see a healthcare professional. A positive viral COVID-19 test (molecular or antigen test) indicates that the individual tested has COVID-19 and can transmit it. If the test result is positive, you should remain at home and away from others. This recommendation does not change if a second test is negative. Refer to If You Are Ill or Test Positive for the COVID-19 Virus.
After obtaining a positive result, it is generally not advised to do additional testing. However, those who work in health care and long-term care should adhere to testing guidelines unique to these settings. Refer to the Health Advisory: Antigen-Based Tests for SARS-CoV-2 Detection (PDF).
Molecular tests
PCR, nucleic acid amplification tests (NAATs), and other forms of molecular amplification detect the virus’s genetic material.
The most accurate diagnostics for finding the virus that causes COVID-19 is molecular testing.
They can be utilized regardless of the presence of symptoms.
They are administered through nose swabs, oral (throat) swabs, or saliva samples.
Nasal swab
A nasal swab looks like a long Q-tip. It is placed approximately two inches into the nose and spun for several seconds. The swab is then extracted and sent to a laboratory for analysis. Nasal swabs are a fast and accurate alternative for the majority of people. While the swab is in your nose, you may feel a tickling sensation, and once it is removed, you may sneeze or have watery eyes for a moment or two. Health care providers are more likely to utilize nose swabs that reach deeper into your nasal cavity, and you may experience greater discomfort than when performing a nasal swab at home.
Saliva tests are self-administered, meaning that you will administer them independently after you are shown how to take the test. The test will be completed by spitting multiple times into a funnel linked to a tube and then screwing on a cap. If you are at a community testing site, you will provide your sample to a supervisor; if you are performing the test at home, you will place the sample in a pre-paid UPS envelope and mail it. Most individuals require 10 to 12 minutes to produce enough saliva to fill the tube. Saliva tests are more comfortable than nasal swabs and just as accurate. Still, persons with limited saliva production, such as very young children or those who have undergone a stroke, may not be ideal candidates.
COVID-19 is confirmed when a positive PCR, NAAT, or other molecular amplification test result is obtained.
Antigen tests
- Antigen assays, often known as fast tests, search for particular proteins on the surface of a virus.
- Antigen tests yield faster findings than other tests.
- They are administered using a nasal swab.
- A positive antigen test result indicates that an individual has COVID-19.
- Visit COVID-19 Self-Testing for more information on home-performable fast tests.
- Evaluation of prior infection
Antibody analyses
Antibody testing, also known as serology tests, examines the blood for antibodies that combat the virus that causes COVID-19. Blood can contain antibodies from a previous infection or vaccination.
Examine blood obtained through a fingerstick or blood draw.
A positive antibody test indicates that a person may have COVID-19 antibodies from a previous infection or COVID-19 vaccination.
What antibody testing is unable to reveal
An antibody test cannot detect the presence of COVID-19. If you have a negative antibody test result, this does not always mean you do not have COVID-19. A molecular or antigen test is required to identify if you currently have COVID-19.
Antibody tests cannot determine if a person will contract COVID-19 again. We do not know how long COVID-19 virus-specific antibodies persist or whether they can prevent future infections.
Most antibody tests cannot differentiate between antibodies acquired from illness and vaccination.
A comparison of their distinctions
Since the samples are acquired similarly for both types of testing, the primary variation between them is in how they are processed.
Antigen testing, often known as “quick tests,” can be performed almost anywhere, including at home, in a doctor’s office, or a pharmacy. Molecular tests are typically more accurate and need a longer processing time in a lab. Antigen test results can be obtained in around 15 minutes. However, they are typically less reliable.
Health care practitioners often rely on molecular tests, especially when COVID-19 symptoms are present, whereas antigen testing is frequently employed when rapid results are required or for routine screening and surveillance.
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