Figure 4.

Rapid salivary test (RST) based on lateral flow assay (LFA). (a) The rapid antigen test recognizes the presence of a specific viral antigen, such as the spike protein. Briefly, the salivary sample is applied to a sample pad diluted with a specific buffer, where it runs along the nitrocellulose membrane reaching the absorbent pad placed at the opposite site of the strip. (b) When both the “test-line” (T-line) and the “control line” (C-line) are visible, the test is “positive” (Severe Acute Respiratory Syndrome Coronavirus 2 is present). When only the C-line is visible, the test is “negative.” The test is “invalid” when the C-line is invisible, regardless of the presence of the T-line. This picture represents the proof of concept and the prototype of the diagnostic test published by our group (Azzi, Baj, et al. 2020).