Mantoux Test

Function

The Mantoux Test, also known as the PPD (Purified Protein Derivative) skin test, measures the body's immune response to proteins derived from Mycobacterium tuberculosis. It is a Type IV delayed-type hypersensitivity reaction. If the person has been infected with TB, their T-cells will recognize the PPD and cause a localized inflammatory response (induration).

Why it is Ordered

It is primarily used as a screening tool for Latent Tuberculosis Infection (LTBI). It is often required for healthcare workers, students, or individuals who have been in close contact with someone who has active TB. It helps identify people who are infected but not yet sick, allowing for preventative treatment.

Associated Conditions

• Latent Tuberculosis: Infection is present but the patient is not contagious and has no symptoms.
• Active Tuberculosis: In some cases, the test is positive during active disease, though other diagnostics are required.
• BCG Vaccination History: Individuals vaccinated with the BCG vaccine (common outside the US) may show a positive result without having a true TB infection.
• Immunosuppression: Conditions like HIV or medications like steroids can cause a 'false negative' because the immune system is too weak to react to the test.