Haims: Understanding the many types of COVID-19 tests
While at a friend’s house for dinner the other day, I overheard a conversation about COVID testing. There seemed to be quite a bit of confusion about the testing types and accuracy. With all the talk about COVID-19 on TV and the plethora of information on the internet and within print, it is understandable confusion exists.
First of all, antigens and antibodies are not interchangeable words. Antigens cause the production of antibodies. Should you want to know if you currently have COVID-19, there are a couple types of tests available: molecular tests and antigen tests. If you want to know if you already had COVID-19, you’ll need an antibody test called a serology test. A serology test is a blood test that looks for antibodies within the blood that were produced to fight the virus.
Molecular tests, also called a PCR test, detect the virus’s specific genetic material. While the tests are very accurate and considered the gold standard by the CDC and FDA, they are not without a margin of error. PCR testing (Polymerase chain reaction) is a laboratory technique that, within hours, makes multiple (millions or billions) copies of a specific DNA. This helps scientists study very targeted parts of the selected DNA.
Unfortunately, because the tests require specific equipment and chemicals that are in short supply, test results are often taking considerable amount of time. As such, other tests are being sought. After all, nobody wants to be held in abeyance and find out that every day since they got tested, they stood the chance of infecting many other people. Therefore, the quicker antigen test is being used.
Just like PCR tests, antigen test samples are collected using nasal or throat swabs. Antigen tests detect specific proteins such as the spike proteins found on the surface of the COVID-19 virus. The testing process is much simpler and less labor-intensive than PCR testing. This is because there is not as much chemistry and lab work involved.
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Antigen tests use a technology that is quite similar to that of home pregnancy tests — a process called lateral flow assay. Once the antigen sample is acquired, the sample is combined with proteins that can immediately reveal a visual result. Although turnaround time is a huge benefit, the accuracy is not as high as PCR testing.
As mentioned earlier, an antibody test is used to identify past exposure to a virus. The test can be performed in a doctor’s office, lab, or hospital and results are often available with a few days. According to an article published by Harvard Medical School, “Having an antibody test too early can lead to false negative results. That’s because it takes a week or two after infection for your immune system to produce antibodies. The reported rate of false negatives is 20%. However, the range of false negatives is from 0% to 30% depending on the study and when in the course of infection the test is performed.”
Recently, the NBA helped fund a saliva-based test for the COVID-19 developed at Yale University. The test is called SalivaDirect. It is both affordable and quick. With an expected consumer cost of about $20 and a turnaround time within an hour to 24-hours, depending on the proximity of the lab, the test may help the bottleneck being experienced by other tests.
While the tests are highly accurate, researchers at Yale expect the tests to soon be accurate at least 90% of the time. Unlike molecular tests and antigen tests that require trained personnel to acquire samples and expensive PPEs for protection while placing swabs deep into people’s nose, saliva samples can be self-administered. For health care workers, schools, and other people needing routine screening, this could be a game-changer.
Unfortunately, at this time, there are no testing methods that are completely accurate. False negative and false positive tests do occur. While we are all reaching our wits-end with this pandemic, please remain vigilant in exercising precautions to avoid exposure. Yes, wearing masks is frustrating and 6 feet of personal space is challenging. However, contributing to anything that could intensify and lengthen our current situation could be catastrophic psychologically and economically.
If you want to get tested, speak to your medical provider, and discuss available options. However, please remember that hospitals are not testing facilities for the general public. Please do not show up to the hospital and expect to be tested.