PPD test

The PPD test is the tuberculin test. It is a skin test based on the principle of type IV allergy, used to detect the presence or absence of tuberculosis in the body. Any body infected with Mycobacterium tuberculosis will produce corresponding sensitized lymphocytes with the ability to recognize Mycobacterium tuberculosis. When a small amount of Mycobacterium tuberculosis or tuberculin is encountered again, sensitized T lymphocytes are re-stimulated by the same antigen to release a variety of soluble lymphokines, resulting in increased vascular permeability and local accumulation of macrophages, resulting in infiltration. Within 48 to 72 hours, there was a local positive reaction of red and swollen hard knots. If the subject has not been infected with Mycobacterium tuberculosis, no local allergic reaction occurs. Basic Information Specialist classification: growth and development check classification: immunological examination Applicable gender: whether men and women apply fasting: not fasting Analysis results: Below normal: Normal value: Negative: 1-5mm Weakly positive: 5-9mm Positive: 10-19mm Strong positive: 20 or more - mm Above normal: negative: A negative reaction indicates no tuberculosis infection, but the following should be considered: if the subject is in the early stage of the primary infection, has not developed an allergic reaction, or is suffering from serious tuberculosis, the body has lost the ability to respond, or the subject is suffering from other infectious diseases In such cases, a negative reaction can occur temporarily. Positive: A positive reaction indicates that the body has an allergic reaction to Mycobacterium tuberculosis. In the past, it has been infected with tuberculosis, but it does not indicate a disease. It is also positive for people who have been vaccinated with BCG. Strong positive reactions indicate active infection and should be further examined for tuberculosis. Tips: It is best not to test when fever and fever, so as not to cause false positives. Normal value The average diameter of the induration is negative if it is less than 5mm, and the positive reaction is greater than or equal to 5mm and less than 20mm [5~9mm is weak positive (+), 10~19mm is positive (++)], 20mm or more (+++) or local blisters Necrosis and lymphangitis are strongly positive. Like the old tuberculin, the TB-PPD test can cause systemic reactions in addition to causing local reactions, but it is less common than the former. The negative (-) induration has an average diameter of less than 5 mm. The weak positive (±) induration has an average diameter of 5 to 9 mm. The positive (+) induration has an average diameter of 10 to 19 mm. Strong positive (++) induration with an average diameter of 20 mm or more. Clinical significance Abnormal results: Some rheumatic diseases are closely related to tuberculosis infection, such as nodular erythema, reactive arthritis caused by tuberculosis infection, etc. Sometimes anti-tuberculosis treatment is needed in the treatment of rheumatic diseases. One of the important indicators for judging whether there is tuberculosis infection is the PPD test. People who need to be examined: infants and young children are often used for the selection and monitoring of BCG vaccination; people with tuberculosis infection; patients with rheumatic diseases closely related to tuberculosis infection can be tested. Positive results may be diseases: tuberculous pleurisy, tuberculous dry pleurisy, stomach tuberculosis Contraindications before examination: It is best not to test when fever and fever, so as not to cause false positives. Requirements for examination: After 72 hours, the negative reaction and the general positive reaction (piggy > 5mm not more than 10mm) can return to normal life. Strong positives can be given prophylactic treatment under the guidance of a doctor. If there are blisters in the area, pay attention to protect the wound surface and cover with gauze if necessary. Inspection process Strictly follow the aseptic procedure. Adopt the Mantoux method. Use a 1ml capacity of the blue core syringe, 4-5 needle, not too long, the forefoot 1/3 of the forearm is the best (here the skin is thin and tender, the reaction is sensitive and easy to observe). Avoid scars, blood vessels and wrinkles. The skin was disinfected with 75% alcohol, and 0.1 ml of PPD (containing 5 knots) was injected slowly by intradermal injection. The injection depth should be appropriate. When the dose is accurate, a round orange peel-like skin of 7-8 mm can be locally displayed. Mound (with pores appearing), do not press sputum and soap at the injection site, do not bathe within 72 hours, try to avoid the injection site when washing your face, avoid hormone drugs as much as possible, if there are other reactions, please go to the hospital for examination and treatment. . The results were observed at 48 and 72 hours after the injection, and the longitudinal and transverse diameters of the induration were measured with a caliper, and the average diameter of the induration = (longitudinal diameter + transverse diameter)/2. Not suitable for the crowd Inappropriate people: 4 to 8 weeks of initial infection with tuberculosis, severe malnutrition, malignant tumors, immune deficiency diseases (congenital immunodeficiency, AIDS), immunosuppressive users, etc., individual elderly due to abnormal body reactions Low function is also often negative. Therefore a negative result does not represent normal. Adverse reactions and risks There are no related complications and hazards.