COVID-19 is a respiratory disease that can cause serious illness, especially in people who already have diabetes, obesity, or high blood pressure.
Two types of tests are commonly used to detect current SARS-CoV-2 infection, the coronavirus that causes COVID-19.
The first type is polymerase chain reaction (PCR) tests, also known as diagnostic or molecular tests. These may help in the diagnosis of COVID-19 by detecting the coronavirus’s genetic material. The Centers for Disease Control and Prevention consider PCR tests to be the gold standard for diagnosis.
Antigen tests are the second type. They help diagnose COVID-19 by looking for specific molecules on the surface of the SARS-CoV-2 virus.
Rapid tests are COVID-19 tests that provide results in as little as 15 minutes and do not require laboratory analysis. These are usually in the form of antigen tests.
Rapid tests can provide results quickly. But they are not as accurate as PCR tests performed in a lab. Keep reading to find out how accurate rapid tests are and when we can use them instead of PCR tests.
How Results from Rapid COVID test Reliable?
You may be wondering if results from the rapid COVID test are reliable. For example, do they compromise accuracy for speed?
When rapid molecular tests first became available, there were concerns that they were missing many positive cases. Abbott’s rapid ID NOW test was particularly concerning. People who may have been infected with the virus tested negative. This is known as a false-negative result. There is now more real-world evidence suggesting that the test is accurate. According to Abbott, the ID NOW test correctly identified 93 percent of positive samples and over 98 percent of negative samples as compared to standard molecular test findings.
Even so, while standard molecular tests are the gold standard, they are not without flaws.
Rapid antigen tests for the coronavirus are highly specific. A positive test result indicates that you are infected. However, as rapid antigen tests are less sensitive than other tests, there is a higher chance of a false-negative result.
When testing early in the infection, rapid tests are more effective. When the amount of virus in your body (the viral load) is highest, it is the best time to check. A higher viral load increases the likelihood that the test will identify the virus in a sample. The rapid ID NOW test has been shown in manufacturer studies to be more effective when used within 7 days of the onset of symptoms.
We recommend that you confirm a negative rapid diagnostic test result with a standard molecular test while using rapid diagnostic tests. This is especially important if you are having symptoms. If you test positive, you are most likely infected and should contact your healthcare provider for more instructions.
A false-negative result means that the test shows you don’t have COVID-19 when you really do.
Chances of a false negative result from a rapid test
A study analysis published in March 2021 examined the results of 64 research accuracy studies evaluating commercially developed rapid antigen or molecular tests.
The researchers discovered that the accuracy of the tests varied greatly. Here is a description of their findings.
Accuracy for people with COVID-19 symptoms
The tests correctly gave a positive result an average of 72 percent of the time for people with COVID-19 symptoms. The 95% confidence intervals ranged from 63.7 to 79 percent, indicating that the researchers were 95% certain that the average fell between these two values.
Accuracy for people who do not have COVID-19 symptoms
The researchers found that people who did not have COVID-19 symptoms tested positive in 58.1 percent of rapid tests. The 95% confidence intervals ranged from 40.2 to 74.1 percent.
Accuracy during the first week of symptoms vs accuracy during the second week
When performed within the first week of symptoms, rapid tests more accurately provided a positive COVID-19 result. The researchers found that within the first week, rapid tests correctly identified COVID-19 in an average of 78.3 percent of cases.
In the second week, the average fell to 51%.
Chances of a false positive result from a rapid test
False positives are rare in rapid tests. If you test positive for COVID-19 when you don’t have it, this is known as a false positive.
Why is it used if it is less accurate?
By now, you may have got the answer to the question ‘Are results from rapid COVID test reliable?’ Then why should you use them?
Despite the relatively high possibility of getting a false negative result, rapid COVID-19 tests have many advantages over PCR tests.
Rapid tests:
- Provide results in minutes instead of days
- Are more compact and accessible than lab tests
- Are less costly than lab tests
- May not require the use of a specialist or a lab
Rapid COVID-19 testing is available in many airports, arenas, theme parks, and other congested areas to check for potential positive cases. Rapid tests will not catch every COVID-19 case. But they will catch at least some cases that would have gone unnoticed otherwise.
What do you do if you have a negative rapid test result but still have to experience symptoms?
If your rapid test results show that you do not have the coronavirus but do have COVID-19 symptoms, you might have received a false negative. It’s a good idea to double-check your negative result with a more accurate PCR test.
How accurate are the other COVID-19 tests?
PCR checks are more precise than rapid tests in general. CT scans are never used to diagnose COVID-19. Past infections may be diagnosed using antigen tests.
PCR test
COVID-19 is still diagnosed using PCR covid tests, which are the gold standard. According to a January 2021 report, mucus PCR tests correctly identified COVID-19 in 97.2 percent of cases.
Computed tomography (CT) scans
CT scans aren’t commonly used to diagnose COVID-19. But they can help identify COVID-19 by identifying lung problems. They are less practical than other tests and have difficulty ruling out other types of respiratory infections.
CT scans correctly detected a positive COVID-19 case 91.9 percent of the time, but just 25.1 percent of the time a negative COVID-19 case, according to the same January 2021 report.
Antibody tests
Antibody tests look for proteins produced by your immune system, known as antibodies, that indicate previous coronavirus infection. They specifically search for antibodies such as IgM and IgG. Current coronavirus infection cannot be diagnosed using antibody tests.
The IgM and IgG antibody tests correctly detected the presence of these antibodies in 84.5 and 91.6 percent of cases, respectively, according to the January 2021 report.
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The Bottom Line
According to research, the rapid COVID test is reliable most during the first week after symptoms start.
With rapid tests, the risk of obtaining a false negative result is relatively high. There is a 25% risk of having a false negative for people who have symptoms. The risk is approximately 40% for people who do not have symptoms. Rapid tests give false-negative results less than 1% of the time.
A rapid COVID-19 test can be a good way to see if you have the coronavirus that causes COVID-19. If you have symptoms and your rapid test results are negative, you should get your results confirmed with a PCR test.
