A positive TB test typically appears as a raised, red bump at the injection site. This reaction is known as a delayed hypersensitivity response and usually develops within 48 to 72 hours after receiving the test. If the bump is larger than a certain size, usually 5-15 millimeters, it may be considered a positive result. A healthcare provider will measure the size of the bump and evaluate other symptoms, such as chest pain, coughing, fever, or weight loss, to determine if the individual has a latent TB infection or active TB disease. If the test result is positive, further testing, such as a chest x-ray and sputum test, may be needed to confirm the diagnosis and determine the appropriate treatment plan. It is important for individuals with a positive TB test to follow up with their healthcare provider promptly to prevent the spread of the disease and receive necessary medical care.
Why didn t my TB skin test bubble?
If there is no reaction after 2-3 days, you most probably have not been exposed to the TB germ. If there is a reaction, some redness and a small bump will appear on the arm.
What if there is no bubble on TB test?
The test is “negative” if there is no bump (or only a very small bump) at the spot where the fluid was injected. A negative TB skin test usually means that you don’t have TB. In some situations, you may need to have another TB skin test later.
How big is a positive TB skin test?
Induration of 15 mm or more is considered positive in the following cases: Healthy individuals older than four years of age with a low likelihood of TB infection[14]
What does a failed TB test look like?
If you have an Mtb infection, the skin around the injection site should start to swell and harden within 48 to 72 hours . This bump, or induration, may also change color. But the induration’s size, not the color, will determine your results. An induration of less than 5 millimeters (mm) is a negative result.
