Tuberculin test is widely used for the initial clinical judgment of Mycobacterium tuberculosis infection, especially for the diagnosis of incipient tuberculosis with important reference significance. The criteria for reading the results: a nodule with a diameter of ≤4㎜ is negative, 5-9㎜ is weakly positive, 10-19㎜ is positive, and ≥20㎜ or the appearance of blisters or lymphangitis around the nodule is strongly positive. The higher the degree of positive tuberculin test, the greater the significance for the diagnosis of tuberculosis, especially for groups such as infants and adolescents. In general, a negative tuberculin test result in an adolescent basically rules out tuberculosis. However, some special cases are excluded, such as Mycobacterium tuberculosis infection that takes 4-8 weeks to establish a metabolic response, and there is a window period during which the tuberculin test can be negative. In addition, severe malnutrition, HIV infection, measles, chickenpox, and severe bacterial infections can also lead to false negatives.