With the world still dealing with the aftermath and ongoing presence of COVID-19, there is one question more relevant than ever: What COVID-19 test is appropriate for me—diagnostic or antibody? If you are ill, exposed, or just wondering about your immunity, knowing how to distinguish between COVID-19 test types is the important step in informed decision-making for your own health and the health of others.It has already been over five years since the world was initially attacked by the COVID-19 virus, which is rearing its head again in the form of new variants, primarily in the Asian nations, such as Singapore, Hong Kong, and Thailand. India also reported more than 1,000 active cases, while the new variant has spread to the US as well, killing more than 300 individuals, according to the reports.Antibody testing, also known as serology testing, is designed to detect antibodies in your blood. Antibodies are proteins your immune system produces after exposure to pathogens such as viruses, including SARS-CoV-2—the virus that causes COVID-19.This type of testing is not meant to diagnose a current COVID-19 infection. Rather, it identifies whether you’ve previously had the virus or developed antibodies as a result of vaccination. According to the CDC, antibody testing should be conducted 1 to 3 weeks after a suspected infection to allow time for your immune system to produce detectable antibody levels.A positive antibody test may indicate previous exposure or vaccination but not necessarily immunity or protection against reinfection. Nor can it tell you if you are currently infectious or still carry the virus. The FDA has approved certain antibody tests, but not all tests are created equal.When Are Antibody Tests Useful?Antibody tests are usually given for the following reasons:Post-infection diagnosis: If you believe you contracted COVID-19 but were never tested while the illness was active, an antibody test can confirm a past infection.Eligibility to donate plasma: Individuals with high antibody levels can be eligible to donate convalescent plasma, which has been used to treat others with severe COVID-19.Research into post-COVID complications: Doctors may employ antibody tests to aid in the diagnosis of unusual complications such as multisystem inflammatory syndrome, particularly in kids.It's critical to point out that timing is an important factor. Getting tested too early after exposure or infection will provide a false-negative since the body hasn't had time to produce antibodies at the time of the test.Role of Diagnostic TestingDiagnostic tests are different from antibody tests in that they try to establish if you are currently infected with the virus. There are two major categories of diagnostic tests:1. Molecular Tests (PCR/NAAT)PCR tests identify the genetic material (RNA) of SARS-CoV-2, the virus that causes COVID-19. They rely on a very sensitive laboratory method called polymerase chain reaction (PCR) that makes a few viral RNA copies even if it is in small quantities for detection. High sensitivity is characteristic of PCR tests, which are the gold standard for detecting COVID-19. They are usually obtained by performing a nasal or throat swab, although saliva samples are sometimes utilized. Tests are available in as little as a few hours to a few days, depending on the testing lab. PCR testing is particularly useful within the first few days of infection, even at low viral loads. They are not, however, ideal for establishing when to discontinue isolation since they can still be detecting non-infectious viral fragments many weeks after recovery.2. Antigen Tests (Rapid Tests)Rapid antigen tests recognize certain proteins (antigens) on the surface of the virus and are widely used in rapid, home test kits. Although these tests provide immediate results in many cases within minutes—they are less sensitive than the PCR tests, particularly in the case of asymptomatic individuals. A sample is usually taken by a nasal or throat swab. Although less sensitive, rapid antigen tests prove to be very useful in certain situations like big gatherings, school or workplace screenings, and travel, where instant results are required. But if one turns out to be negative using an antigen test but still has symptoms, it is advised to retest within 48 hours or double-check using a more sensitive PCR test.How To Choose the Right COVID-19 Test?A number of factors determine which COVID-19 test you should undergo. If you have a fever, cough, or are tired, a diagnostic test—either PCR or antigen—is warranted to establish an active infection. In recent exposure with no symptoms, the CDC recommends testing five days later with a diagnostic test to detect possible asymptomatic infections. If you wonder whether you had COVID-19 weeks or even months ago, an antibody test might give you some information about past infection. For vaccinated individuals who need to test for immune response, antibody testing will show partially that you have antibodies, but it won't prove immunity. If you're traveling or going to a function, certain test types will be needed, so you'll need to look at the rules ahead of time. How Accurate Are COVID-19 Tests?PCR Tests: Very sensitive and highly accurate, they can pick up even tiny amounts of viral RNA. Taking the test too soon, though—before a sufficient amount of virus is in the system—may yield a false-negative. Antigen Tests: Quick and inexpensive, but more likely to be false-negatives, particularly when taken too soon. To have better accuracy, repeat testing every 48 hours is advisable.Antibody Tests: Timing and quality determine accuracy. Too early, antibodies may be missed, and not all tests are FDA-approved.After COVID-19 When Should You Test Again?If you have recovered from COVID-19 and wish to determine your immunity level, an antibody test can identify the level of IgM, IgG, or IgA antibodies in your blood. However, health professionals advise against concluding that a positive result on an antibody test is a guarantee of long-term protection.In the U.S., organizations like the American Red Cross are still conducting antibody testing on donor blood to identify potential plasma donors. If you're interested in helping others post-recovery, this could be a way to contribute.COVID-19 testing isn't one-size-fits-all. Knowing which test to take and when can make all the difference in getting accurate information and taking appropriate action.If you have symptoms or have known exposure, have a diagnostic test. If you're interested in previous exposure or potential immunity, have an antibody test—but be realistic.