The PPD test is a tuberculin test. A strong positive PPD test suggests that the organism may be in the active stage of tuberculosis or has been previously infected with tuberculosis, but a strong positive PPD test is not the absolute gold standard for the diagnosis of tuberculosis. The PPD test is a test to observe whether the body produces a hypersensitivity reaction to Mycobacterium tuberculosis through inoculation with a tuberculin skin test. A strong positive PPD test suggests that the body is infected with Mycobacterium tuberculosis or has been infected with Mycobacterium tuberculosis in the past or has been vaccinated with the BCG vaccine. Children within three years of age who have not been vaccinated with BCG vaccine have a strong positive PPD test suggesting active tuberculosis. In the case of adults, it is also necessary to make a comprehensive judgment based on the presence of cough, low-grade fever, abnormal sweating after going to sleep and stopping sweating after waking up, and emaciation, combined with chest CT to find out whether there is tuberculosis infiltration, blood sedimentation, and sputum test for antimicrobial bacilli, etc. The detection of tuberculosis bacilli in sputum can confirm the diagnosis of active pulmonary tuberculosis. In conclusion, it is recommended to consult a doctor in time when PPD test is detected, make a clear diagnosis under the guidance of a specialist, and treat the cause of the disease.