Antibody to *Mycobacterium tuberculosis* (IgG) – Serum

What Does This Test Measure?

The test detects IgG antibodies specific to *Mycobacterium tuberculosis*. These antibodies develop when your immune system encounters the bacterium, often after an initial infection or vaccination (like BCG). The presence of these antibodies suggests past exposure, but they do not confirm active TB. This test is typically used alongside other tests (such as a TB skin test or sputum culture) for a complete evaluation.

Why Might You Need This Test?

Your healthcare provider may order this test if you have risk factors for TB, such as living or working in a high-risk area, having traveled to regions with higher TB rates, or being in close contact with someone who has active TB. It can also be used to monitor immunity after vaccination or assess past exposure in certain clinical scenarios.

How Is the Test Performed?

A small blood sample is taken from a vein in your arm. The blood is sent to a lab where it is tested for the presence of TB-specific antibodies using an immunoassay method. Results are typically available within a few days.

What Do the Results Mean?

A positive result indicates the presence of TB-specific antibodies, suggesting past exposure to *Mycobacterium tuberculosis*. However, this does not always mean you have active TB. A negative result means no detectable antibodies were found, which may mean you have never been exposed or have been exposed long ago. Interpretation depends on clinical context, including travel history, vaccination status, and symptoms.