The purpose of the tuberculin test is to screen for tuberculosis infection and is a common ancillary test for the clinical diagnosis of tuberculosis. The tuberculin test is currently the more commonly used method for diagnosing tuberculosis and is one of the most important clinical skin tests available. The tuberculin test is performed by injecting 0.1 ml of tuberculin into the skin on the palmar side of the anterior wall, observing the local reaction at the injection site within 48 to 72 hours after injection, and measuring the transverse diameter and vertical diameter of the local hard nodes, which are positive if the average diameter of the hard nodes is more than 5 mm, average positive if they are 5-9 mm, moderate positive if they reach 10-19 mm, and positive if they reach more than 20 mm and have local symptoms of blistering, hemorrhage, necrosis and lymphangitis are strongly positive. Tuberculin is widely used for tuberculosis investigation and monitoring. If the tuberculin test is positive, it means that the person has been infected with tuberculosis bacteria, but it is not yet confirmed whether he has tuberculosis, because positive results can also occur in patients cured of tuberculosis, and people who have been injected with BCG vaccine can also show a positive tuberculin test, but a strong positive result indicates that the organism currently has active tuberculosis. Therefore, for those who have a positive tuberculin test, it needs to be analyzed in conjunction with clinical manifestations, bacteriological examination of sputum, chest X-ray or CT examination, etc. to make a final judgment. Tuberculin test is of reference significance for the diagnosis of tuberculosis in children, adolescents and young adults. However, if the test result is positive, it does not necessarily mean that the disease is present and further examination is needed.