Waiting for a coronavirus test result can vary from less than an hour to a maximum of one week, depending on the type of COVID-19 test you are taking. Many people choose the rapid test to get immediate results, but how accurate are these rapid turnaround tests?
“Tests that are fast, usually deliver results within 30 minutes, are not as sensitive as the traditional test that is sent to the laboratory and generally takes half a day to several days to get a result,” Dr. Romney Humphries, Ph.D. D., Director of Clinical Microbiology Laboratory at Vanderbilt University Medical Center, told Fox News.
“There’s a 75-80% detection rate for rapid testing compared to 90-95% with traditional, lab-based testing.” Humphries, also a member of the Society of Infectious Diseases of America, added.
Humphries admitted that the ability of the rapid test to correctly identify those with the disease – sensitivity to testing – may not always be clinically relevant.
“Some studies have shown that rapid tests lack low levels of virus. A patient may have low levels of the virus if they are early in the course of infection before the virus had a chance to replicate itself, or at the end of the infection when the infection disappears. “
Humphries, also a professor of pathology, microbiology and immunology at Vanderbilt University Medical Center, notes that this could be a potential problem with the spread of the virus.
“In the former case, the lack of a positive is problematic, because that is a patient who can then infect others, thinking that they are negative. In the latter case, the low levels of virus may indeed be dead viruses, and that patient may not be contagious. “
Although the waiting time for the results of the two tests differs, the technique appears similar in terms of swabbing the nasal passage.
According to the US Food and Drug Administration (FDA), the antigen test – commonly known as the “rapid diagnostic test” where results are given within minutes to an hour – detects specific proteins on the surface of the virus. It is usually very accurate, although more likely to miss an active infection compared to the molecular test, the FDA stated on its website.
Some studies have shown that rapid tests lack low levels of virus.
Meanwhile, the molecular test, also known as the RT-PCR test, nucleic acid amplification test (NAAT), as a diagnostic test, detects the genetic material of the virus and can typically last up to a week to a week, depending on demand. at the lab. According to the FDA, this test is very accurate and does not normally need to be repeated. The FDA advises if you have symptoms, but your rapid antigen test is negative, your healthcare provider may want to order a molecular test to see if you actually have an active infection.
What test Humphries prefers: ‘I think the laboratory test with longer results is preferable, if possible. That being said, there are times when this is not possible, and the rapid tests in the right context work well, ‘she said.
“The rapid tests play an important role and can be very valuable in some cases. For example, a patient who needs trauma surgery may not wait a day or two for test results because doctors need to know the results before performing a life-saving, emergency procedure. Many hospitals use rapid testing for this purpose.
“Another example is screening people for an event – or possibly using them before going to school – theoretically a rapid test would be valuable in those contexts, although this application of rapid tests is not common,” Humphries added.
The microbiologist warned that no test is perfect and everyone has their limitations.
“One factor that affects every COVID test is getting a really good sample. To collect a proper sample of nasal pharyngeal, the tester must get enough back into the nose to cause a gag reflex, because that is where the coronavirus is. They need to go deep. In principle, the chances of a more accurate test result with a better sample increase, ”she stated.
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