Did you find this answer helpful? Subscribe to keep up with all things Lifelong Learning.
What are the likely causes of a false positive lateral flow? Is this more likely if I have another (non-COVID) virus? Is a faint like positive on lateral flow more likely to be false positive? NOT asking because I want to discount a LF positive but because I have just had positive LF and negative PCR, so want to understand this
Lateral flow tests are a low-cost, simple, rapid, and portable test that is most familiar to people as the same technology as the urine pregnancy test. It basically involves taking a fluid sample (e.g., urine, blood, saliva, etc.) and placing them on a specialized “paper” strip that has the test “reagents” (also called analyte) embedding into it. The fluid wicks along the test strip and “reacts” to those embedded reagents, such as antibodies against COVID-19, and according to which reagents there will be a reaction that will make a recognizable color visible on the test strip.
For a urine pregnancy test, there can be false negative and false positive test results; a person is instructed to “confirm” any positive urine pregnancy test with a more sensitive test by their physician. There can be many reasons for a false positive test but that is the inherent “weakness” of the test. In the same way, the lateral flow assays for COVID-19 are less sensitive and less specific than other more specialized/complex tests such as those at commercial laboratories. However, the trade-off is that the lateral flow assay can be a home-based test and/or can be used without an expensive/specialized support lab.
