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.
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:
Related Articles
How reliable are covidSHIELD test results?
In a recent study, the saliva test was shown to have a specificity of 98.9% and a sensitivity of 95.8%. The FDA-authorized covidSHIELD test targets three highly conserved regions of the viral genome for detection. High specificity offered by ...I tested positive with covidSHIELD and negative with nasal PCR or other test. Which result is correct?
Not all PCR tests are the same. They run on different PCR instruments, use different reagents, look for different genes, etc. etc. For example, the covidSHIELD saliva test is more reliable overall compared to self-collected nasal specimens. Nasal PCR ...I don't have any symptoms. Is this a false positive?
It is extremely unlikely for the covidSHIELD test to produce a false positive result. In a recent study, the saliva test was shown to have a specificity of 98.9% and a sensitivity of 95.8% which makes it one of the most accurate tests in the world. ...Could something I ate have caused a false positive?
No. SHIELD Illinois encourages everyone to refrain from eating or drinking for 60 minutes before the test to prevent the specimen from being rejected by the lab or producing a result of INVALID. Eating or drinking before the test would not cause an ...Will covidSHIELD catch variants? Delta? Omicron? Can I tell which variant I have?
Based on all available information, the covidSHIELD test will be able to identify that a specimen which is positive for the Omicron variant contains SARS-CoV-2 (i.e. the Omicron variant will not cause a false negative). The covidSHIELD test looks for ...