A: The false negative rate is the % of infected individuals who incorrectly test negative for COVID. For example, a hot-off-the-press NPR article reports a 15% false negative rate for Abbott’s new rapid COVID test. A 15% false negative rate indicates that out of 100 infected individuals, 15 would incorrectly test negative.
How do we assess the false negative rate? We give a sample of individuals two tests — a newly available test along with a benchmark “gold standard” — the best test currently available. Often the gold standard is very expensive, invasive, and/or tricky to process, motivating the creation of a new test. The false positive rate captures the proportion of individuals testing positive with the gold standard who test negative with the new test.
Note that the false negative rate for a test can differ widely across ideal versus less-ideal testing conditions.
A high rate of false negatives will provide a false sense of security, perhaps leading to infected individuals unintentionally and unknowingly spreading the disease as they return to work and social activities.
We also worry about false positive rates — the proportion of healthy individuals who incorrectly test positive for COVID — stay tuned for a related future post!
