A lot of people have asked me about the specificity and sensitivity of the current COVID-19 rapid tests, and the data was a little gappy. This study answers some questions. TLDR: specificity is great (99.6%)! sensitivity is complicated (34.5% overall). symptoms + pos test is most certain. 🧪
The decline in RDT sensitivity throughout the pandemic can primarily be attributed to the reduced prevalence of symptomatic infections among vaccinated individuals and individuals infected with Omicro...
What do I mean by “complicated”? Sensitivity of the test was lower if the testee was: - asymptomatic vs. either typically or atypically symptomatic - vaccinated vs. unvaccinated* - infected with a newer variant (notably, this wasn’t actually statistically significant, only trending) *see next post
Let’s say the prevalence is 1%, sensitivity 34% and specificity 99.6%. 100k people are tested, 1000 have the disease. Of those 340 will be +, 660 -. Of the 99k healthy people 396 will be +, 98604-. If you test +, you have <50% probability you have the disease.
That sensitivity isn't great, especially considering the study looked at tests run in a hospital, presumably collected and run by trained individuals, as opposed to home testing.