What does a negative TB skin test look like?

What if my TB skin test is negative? 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 indicates a positive TB skin test?

Positive skin test: This means the person’s body was infected with TB bacteria. Additional tests are needed to determine if the person has latent TB infection or TB disease. Negative skin test: This means the person’s body did not react to the test, and that latent TB infection or TB disease is not likely.

How do you read a positive Mantoux test?

The reaction is read by measuring the diameter of induration (palpable raised, hardened area) across the forearm (perpendicular to the long axis) in millimeters. If there is no induration, the result should be recorded as “0 mm”. Erythema (redness) should not be measured.

Is it normal to bruise after a TB skin test?

Induration is the key item to detect, not redness or bruising. Read skin tests 48-72 hours after the injection when the size of the induration is maximal.

What happens if I scratched my TB skin test?

After the test Some redness at the skin test site is expected. The site may itch, but it is important that you do not scratch it, since this may cause redness or swelling that could make it hard to read the skin test.

What happens if TB skin test is injected too deep?

For an intradermal injection, the needle bevel is advanced through the epidermis, the superficial layer of skin, approximately 3 mm so that the entire bevel is covered and lies just under the skin. The injection will produce inadequate results if the needle angle is too deep or too shallow.

What should your skin look like after a TB test?

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.