There are various methods to rule out tuberculosis, and one of the most effective and convenient methods is the tuberculin test. This is done by subcutaneously injecting a pure protein derivative and observing the injection site for redness and hard nodules. Although the tuberculin test is not crucial to confirm the diagnosis of tuberculosis, the absence of redness and hard nodules can rule out tuberculosis, and its more meaningful to rule out tuberculosis. Tuberculosis can also be ruled out on the basis of pulmonary imaging, which is more important for early tuberculosis diagnosis. If there is no significant abnormality or no tuberculous changes on pulmonary imaging, tuberculosis can be ruled out. However, in clinical work there are many difficulties to identify TB with pneumonia and lung cancer, so other means of identification are also needed.