That’s basically the FDA suggesting people follow the instructions and avoid cross contamination. The relevant paragraphs are:
In general, antigen tests are not as sensitive as molecular tests. Due to the potential for decreased sensitivity compared to molecular assays, negative results from an antigen test may need to be confirmed with a molecular test prior to making treatment decisions. Negative results from an antigen test should be considered in the context of clinical observations, patient history and epidemiological information.
Like molecular tests, antigen tests are typically highly specific for the SARS-CoV-2 virus. However, all diagnostic tests may be subject to false positive results, especially in low prevalence settings. Health care providers should always carefully consider diagnostic test results in the context of all available clinical, diagnostic and epidemiological information. Test interference from patient-specific factors, such as the presence of human antibodies (for example, Rheumatoid Factor, or other non-specific antibodies) or highly viscous specimens could also lead to false positive results.
