Sensitivity vs. Limit of Detection of rapid antigen tests
In this situation, &quot;sensitivity&quot; refers to how often the test is able to correctly detect the presence of analyte. A test with high sensitivity means that there are few false negatives.
Limit of detection refers to how much of the analyte must be present before it is considered positive.
Imagine two different tests: test A uses an antibody with very high affinity for a specific spike protein sequence. Because of the high affinity, it can detect the spike protein even when there's not much around (good limit of detection). However, the antibody is less robust against other sequences, so it sometimes reports a false negative in the presence of spike protein variants (poor sensitivity).
Conversely, test B has an antibody with medium affinity for several different spike protein variants. It relies on high levels of the protein being present, but it works with many different variants and rarely gives false negatives. This test would have a high (aka poor) limit of detection and high (aka good) sensitivity.