What is covidSHIELD’s false positive rate? I heard the test is no more accurate than a coin flip, or 50/50. Is that true?
The answer to that is, unequivocally, "no."
And it is wrong by a long shot. Let me explain:
- In a perfect world, we would know the exact number of infected people, which would be the starting point in making such a calculation. Without knowing that number, it is difficult to calculate an exact overall false-positive rate.
- However, we have real-world data from the University of Illinois Urbana-Champaign testing program that suggests that the number of false positives is extremely low.
- Since we started testing in July 2020, we have conducted 2,354,721 tests and identified 7,748 cases (see https://go.illinois.edu/COVIDTestingData for the latest data). That means 0.3% of tests were positive.
- Case investigators have found that 90% of those cases develop symptoms, leaving approximately 774 that are completely asymptomatic.
- If all of those asymptomatic cases were false positives, which is highly unlikely, that would be a specificity of 99.96%, or four false positives per 10,000 tests, at the most.
- If we use that worst-case specificity number, the probability that a positive result is a true infection would be 98%.
- Also making it extremely unlikely for a false positive to occur: The test targets three genes within the virus for detection. Three.
- The high specificity offered by three-target detection, combined with frequent testing, makes the SHIELD saliva-based test extremely accurate and one of the best tests available.
While no test is perfect — that includes nasal swab and saliva tests — clearly covidSHIELD is as close as you can get.
For more information on the accuracy of covidSHIELD test results visit: