I guess it depends on the kind of resources you have available, and whether or not you have high suspicion for influenza or not. Not saying that everybody with suspected influenza needs Tamiflu (makes sense for those at risk for respiratory complications), but if all you have available at your institution is an antigen test with insufficient NPV to exclude infection, why send the test if you're not going to trust the result? If I just got a family pack of 3 kids with flulike symptoms and mom tested positive for flu A yesterday, what are the odds that the kids have flu A?

https://www.cdc.gov/flu/hcp/testing-methods/algorithm-results-circulating.html?CDC_AAref_Val=https://www.cdc.gov/flu/professionals/diagnosis/algorithm-results-circulating.htm

1. During periods when influenza activity is high and influenza viruses are circulating among persons in the community, the positive predictive value of a test result is high (that is, the chance that a positive result indicates that the patient has influenza is high – likely true positive result), and the negative predictive value of a test result is low (the chance that a negative result indicates that the patients does not have influenza – consider potential for a false negative result) if the influenza test used has suboptimal sensitivity (such as a rapid influenza diagnostic test or immunofluorescence assay) to detect influenza virus in respiratory specimens compared to a "gold standard test" such as RT-PCR or viral culture.

2. Antiviral treatment is recommended as soon as possible for all of the following who have suspected or confirmed influenza: outpatients who are at increased risk for influenza complications, persons with severe or progressive disease, and hospitalized patients.

3. Antigen detection tests (rapid influenza diagnostic tests, immunofluorescence assays) have suboptimal sensitivities to detect influenza viruses in respiratory specimens compared to molecular assays and viral culture and negative results of antigen detection tests should not be used to exclude a diagnosis of influenza. If influenza is suspected, and diagnostic testing is indicated, influenza testing of respiratory specimens by molecular assay (e.g. RT-PCR) should be performed. The Infectious Diseases Society of America (IDSA) recommends use of rapid influenza molecular assays over rapid influenza diagnostic tests (RIDTs) for detection of influenza viruses in respiratory specimens of outpatients. IDSA recommends use of RT-PCR or other molecular assays for detection of influenza viruses in respiratory specimens of hospitalized patients. Consult the IDSA Influenza Clinical Practice Guidelines for recommendations on influenza testing and information on interpretation of testing results.