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In the most basic sense, there are four possible outcomes for a COVID-19 test, whether it’s molecular PCR or rapid antigen: true positive, true negative, false positive, and false negative.
Accuracy varies among each test, but Ellume says that its test has a 96 percent accuracy rate in detecting symptomatic cases of COVID-19 and 91 percent accuracy in detecting asymptomatic cases ...
A false positive Covid-19 test result can happen, but it’s rare, says Brian Labus, Ph.D., M.P.H., assistant professor at the University of Nevada Las Vegas School of Public Health.
Test errors can be false positives (the test is positive, but the virus is not present) or false negatives, (the test is negative, but the virus is present). [179] In a study of over 900,000 rapid antigen tests, false positives were found to occur at a rate of 0.05% or 1 in 2000.
Antigen tests can be analyzed within a few minutes. Antigen tests are less accurate than PCR tests. It has a low false positive rate, but a higher false negative rate. A negative test result may require confirmation with a PCR test. [8] Advocates claim that antigen tests are less expensive and can be scaled up more rapidly than PCR tests. [8]
The test has a false positive rate of 5% (0.05) and a false negative rate of zero. The expected outcome of the 1,000 tests on population A would be: Infected and test indicates disease (true positive) 1000 × 40 / 100 = 400 people would receive a true positive Uninfected and test indicates disease (false positive)
The first is a reverse-transcription polymerase chain reaction test, or RT-PCR. This is the most common diagnostic test used to identify people currently infected with SARS-CoV-2.
COVID-19 rapid antigen tests (RATs) have been widely used for diagnosis of COVID-19. The World Health Organization (WHO) COVID-19 Case Definition states that a person with a positive RAT (also known as an antigen rapid diagnostic test or Antigen-RDT) can be considered a "confirmed case of SARS-CoV-2 infection" in two ways. [10]