A normal person may have a negative or positive tuberculosis skin test. When performing a tuberculin test, the size of a localized hard nodule in the skin is usually used to determine whether it is negative or positive. It is negative if the diameter is less than 5mm, weakly positive if 5-10mm, moderately positive if 10-15mm, and strongly positive if 15mm or more, so anything larger than 5mm can be defined as positive. As a result of BCG vaccination, most people are negative or positive, both can be normal. Manifestations such as skin redness and swelling only are defined as negative. However, it is possible for a normal person to present with greater than 5mm defined as positive without tuberculosis infection. In the case of strong positivity and suspicion of tuberculosis it is necessary to continue the examination by performing a CT of the lungs, etc. The exact diagnosis needs to be made by a doctor.