Molecular — Also known as a PCR (polymerase chain reaction) test, this test detects whether genetic material of the virus is present in the sample collected from your throat or sputum (the back of your sinuses)
Antigen — This test, sometimes referred to as "rapid test," detects viral proteins
Antibody — Also known as a serology test, it detects the presence of antibodies in your blood
The first two, molecular and antigen, are so-called "viral tests" that detect active infections, whereas the antibody test will tell you if you've developed antibodies in response to a previous coronavirus infection. It typically takes your body one to three weeks after an infection clears to start making antibodies against the virus in question.
Each of these COVID-19 tests have their issues and controversies. The problem with antibody testing is that there are seven different coronaviruses known to cause respiratory illness in humans.2 Four of them cause symptoms associated with the common cold:
229E
NL63
OC43
HKU1
In addition to the common cold, OC43 and HKU1 — two of the most commonly encountered betacoronaviruses3 — are also known to cause bronchitis, acute exacerbation of chronic obstructive pulmonary disease and pneumonia in all age groups.4 The other three human coronaviruses — which are capable of causing more serious respiratory illness — are:
SARS-CoV
MERS-CoV
SARS-CoV-2
The tricky part is that the antibodies created by these different coronaviruses appear very similar, and the U.S. Centers for Disease Control and Prevention admits recovering from the common cold can trigger a positive antibody test for COVID-19, even if you were never infected with SARS-CoV-2 specifically. As explained on the CDC's "Test for Past Infection" web page:5
"Antibody tests check your blood by looking for antibodies, which may tell you if you had a past infection with the virus that causes COVID-19. Antibodies are proteins that help fight off infections and can provide protection against getting that disease again (immunity). Antibodies are disease specific …
A positive test result shows you may have antibodies from an infection with the virus that causes COVID-19. However, there is a chance a positive result means that you have antibodies from an infection with a virus from the same family of viruses (called coronaviruses), such as the one that causes the common cold." ...<<<Read The Full Article Here>>>....