A negative antibody to Mycobacterium tuberculosis does not exclude tuberculosis. The current gold standard for diagnosing tuberculosis is the detection of Mycobacterium tuberculosis in sputum. If TB bacilli are not detected in sputum, the patient has symptoms of TB, such as cough, sputum, coughing up blood, low-grade fever, night sweats, wasting, weakness, and loss of appetite. In addition, a positive TB-SPOT or increased hematocrit in ancillary tests, and a chest CT presentation consistent with a prevalent site of TB or imaging changes of TB are usually still highly suspicious of TB, in which case empirical anti-TB therapy is usually given. Therefore, TB antibodies are not a diagnostic criterion for TB, i.e., negative TB antibodies do not exclude TB.