In lateral flow tests, what is the expected visual output of a negative result?

In lateral flow tests, the expected visual output of a negative result is characterized by the visibility of only the control line. The control line serves as an internal validation that the test is functioning correctly. Its appearance indicates that the sample has been processed adequately and that the reagents are working as intended.

In a negative result context, the lack of a test line means that the target analyte was not present in the sample at detectable levels. Therefore, the only indicator that is expected to be visible is the control line, reinforcing that while the test itself has performed properly, the test has not detected the specific substance being tested for.

This is a critical aspect of interpreting lateral flow tests, as it ensures users can trust the result; the control line must always show up, regardless of whether the test line does or not. The other visual outputs, such as both lines appearing or no lines being visible, do not correspond to a standard interpretation for a negative result in these tests.