What does a negative tuberculosis test look like?

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.

What positive TB test looks like?

A positive TB skin test will look like a firm, red bump. Your provider will measure the size of the firmness of the bump (induration). Your provider considers your particular risk factors to determine the results of your test.

What does a negative TB test look like after 48 hours?

If the area of skin where you received the PPD injection isn’t swollen or is only slightly swollen 48 to 72 hours after the injection, the test results are negative. A negative result means that you most likely haven’t been infected with the bacteria that cause TB.

How can you tell if a TB test is positive or negative?

If you have a raised, hard bump or there’s swelling on your arm, you have a positive test. That means TB germs are in your body. But it doesn’t always mean you have active tuberculosis disease.

Can a negative TB test be red?

Redness alone at the skin test site usually means you have not been infected with TB bacteria. A firm red bump may mean you have been infected with TB bacteria at some time. The size of the firm bump (not the red area) is measured 2 to 3 days after the test to determine the result.

How do you read TB skin test?

In a healthy person whose immune system is normal, induration greater than or equal to 15 mm is considered a positive skin test. If blisters are present (vesiculation), the test is also considered positive. In some groups of people, the test is considered positive if induration less than 15 mm is present.

Is my TB test supposed to be red?

Results. Redness alone at the skin test site usually means you haven’t been infected with TB bacteria. A firm red bump may mean you have been infected with TB bacteria at some time. The size of the firm bump (not the red area) is measured 2 to 3 days after the test to find out the result.

Does redness mean positive TB test?

It does not mean you have an active TB infection. The test may be seen as positive if the skin where you were injected is hard, raised, red, and swollen. But redness alone is not considered a positive test result. In many cases, a healthy immune system will surround the TB bacteria soon after you are infected.

Why is my TB test site Red?

Redness alone at the skin test site usually means you haven’t been infected with TB bacteria. A firm red bump may mean you have been infected with TB bacteria at some time. The size of the firm bump (not the red area) is measured 2 to 3 days after the test to find out the result.

What if your TB test turns red?