A negative test result for influenza A and B means that influenza A and B infection is not supported. However, clinical judgment needs to be integrated with the patient’s actual condition and the methods used to test for influenza A and B. The most commonly used method for rapid detection of influenza A and B in outpatient clinics is the immunofluorescence method, which has a degree of false negatives. This means that a negative result for influenza A or B cannot completely rule out influenza A or B infection. If influenza A or B infection is highly suspected, further PCR tests are needed to clarify the diagnosis.