What is a PPD skin test used to diagnose?

A PPD (purified protein derivative) skin test is used to diagnose tuberculosis (TB). It is also known as the Mantoux test. The PPD skin test is a way to check if a person has been infected with the bacteria that causes TB.

The test involves injecting a small amount of PPD, which is a purified protein derived from the TB bacteria, into the skin. If a person has been infected with TB, they will usually develop a small, hard, raised bump at the injection site within 48 to 72 hours. The size of the bump is measured and used to determine if the person has TB infection.

A positive PPD skin test does not necessarily mean that a person has active TB disease. It may indicate that the person has been infected with TB bacteria but has not developed active disease. Further tests, such as chest X-rays and sputum tests, may be needed to determine if a person has active TB disease.

The PPD skin test is a valuable tool for diagnosing TB infection, and it is widely used in many countries.