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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.
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.
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 ...
The false positive rate (FPR) is the proportion of all negatives that still yield positive test outcomes, i.e., the conditional probability of a positive test result given an event that was not present. The false positive rate is equal to the significance level. The specificity of the test is equal to 1 minus the false positive rate.
The log diagnostic odds ratio can also be used to study the trade-off between sensitivity and specificity [5] [6] by expressing the log diagnostic odds ratio in terms of the logit of the true positive rate (sensitivity) and false positive rate (1 − specificity), and by additionally constructing a measure, :
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.