IMO, you can be confident about positive home test results. Negative test results early on could be false negatives (see below).
The FDA recommends repeat testing following a negative result to reduce the risk that a COVID-19 infection could be missed, whether or not you have symptoms.
www.fda.gov
The U.S. Food and Drug Administration (FDA) is advising people to perform repeat, or serial, testing following a negative result on any at-home COVID-19 antigen test, to reduce the risk an infection may be missed (false negative result) and to help prevent people from unknowingly spreading the SARS-CoV-2 virus to others.
The FDA recommends repeat testing following a negative result whether or not you have COVID-19 symptoms.
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When you perform an at-home COVID-19 antigen test, and you get a positive result, the results are typically accurate. However, if you perform an at-home COVID-19 antigen test, you could get a false negative result. This means that the test may not detect the SARS-CoV-2 virus that is in your nasal swab sample. This could happen if you test soon after you get an infection, especially if you don't have
COVID-19 symptoms. If you receive a false negative test result, you may unknowingly spread the SARS-CoV-2 virus to others....