What does a positive PPD test indicate?

A positive PPD (Purified Protein Derivative) test indicates that the patient has been exposed to the bacteria that cause tuberculosis (TB) at some point in their life. This test measures the immune response to specific proteins associated with the TB bacteria. When the immune system has been exposed, it will react positively, reflecting past infection or exposure, rather than confirming active disease.

It's essential to understand that a positive PPD test does not diagnose active TB; further investigations, such as a chest X-ray or sputum tests, are required to determine if the person is currently infected and whether they have active TB. Therefore, while the positive result signifies exposure, it does not automatically mean that the patient is sick or infectious, nor does it necessitate immediate hospitalization or treatment without further evaluation.