Tuberculosis screening is performed to detect latent tuberculosis infection. Since tuberculosis is a highly contagious disease, patients are usually screened for tuberculosis by the tuberculin test, also known as the PPD test. Generally, the patient’s response is observed by subcutaneous injection of tuberculin, and if an erythema of less than 5 mm appears within 72 hours, the result is negative. The presence of erythema of 5-10 mm indicates a positive result, and the presence of erythema of 10-20 mm indicates a moderate positive result. A strong positive result is considered if the erythema is >2 cm and blistering is present. Patients with a strong positive result may be patients with a current tuberculosis infection and need to be further examined by the respiratory department.