The PPD test is a skin test used to detect the body's immune response to tuberculosis (TB), commonly known as consumption. This test utilizes a substance called Purified Protein Derivative (PPD), obtained from tuberculosis bacteria. A person who has been infected with tuberculosis develops a specific sensitivity to these proteins. When PPD is injected into the skin, individuals previously infected will exhibit a noticeable immune reaction (redness and swelling). This reaction is typically assessed 48 to 72 hours after injection and indicates the likelihood of tuberculosis infection.
The test is usually performed by injecting a small needle into the inner forearm. Slight redness or swelling at the injection site is normal, and these symptoms typically resolve on their own within a short period.
The PPD test is recommended for individuals at risk, such as those who have been in contact with a TB patient or those with weakened immune systems (e.g., steroid users, cancer or AIDS patients). This test allows for early diagnosis and, consequently, the initiation of more effective treatment processes.