Ppd test

PPD Test

The PPD test (Purified Protein Derivative test), also known as the Mantoux test, is a diagnostic tool primarily used to identify tuberculosis (TB) infection. The test is named after Charles Mantoux, a French physician who developed the method in the early 20th century.

Overview

The PPD test is a type of Tuberculin skin test that measures a person's immune response to the bacteria that causes tuberculosis. The test involves injecting a small amount of tuberculin purified protein derivative (PPD) under the skin of the forearm. After 48 to 72 hours, a healthcare professional will check the injection site for a reaction, which may indicate a TB infection.

Procedure

The PPD test is administered by injecting 0.1 ml of PPD solution into the inner surface of the forearm using a tuberculin syringe. This creates a small, raised bump. The healthcare provider will then check the injection site 48 to 72 hours later to measure the size of any induration (hard, raised area), not redness, which may indicate an immune response to the PPD solution.

Interpretation

The interpretation of the PPD test depends on the size of the induration and the person's risk factors for TB. A larger induration generally indicates a positive result, suggesting TB infection. However, the test cannot distinguish between latent TB infection and active TB disease. Further tests, such as a chest X-ray or Sputum culture, are needed to confirm active TB disease.

Limitations

The PPD test has several limitations. It may produce false-positive results in people who have been vaccinated with the BCG vaccine or infected with non-tuberculosis mycobacteria. It may also produce false-negative results in people with weakened immune systems, such as those with HIV/AIDS or malnutrition, or in the very young or very old.

See also

• Tuberculosis
• Tuberculin skin test
• BCG vaccine
• Chest radiograph
• Sputum culture