What is reading the skin?

"Reading" the skin test means detecting a raised, thickened local area of skin reaction, referred to as induration. 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.

When should the skin test be read?

The skin test reaction should be read between 48 and 72 hours after administration. If the test is not read within 72 hours, another TST should be placed unless the amount of induration is ≥ 10 mm within 7 days after placement.

What is a positive TB test look like?

If you have a reaction to the test, it will look like a raised bump. Your health care provider will measure the size of the reaction. If there is a bump, it will go away in a few weeks.

How long after a TB shot should it be read?

The results should be read between 48 and 72 hours after administration. A patient who does not return within 72 hours will probably need to be rescheduled for another TST. Visually inspect injection site under good light, and measure induration (thickening of the skin), not erythema (reddening of the skin).

What does a negative TB skin test look like?

A negative reaction usually means you have never been infected with the bacteria that cause TB. With a negative reaction, the skin where you received the PPD test is not swollen, or the swelling is very small. This measurement is different for children, people with HIV, and other high-risk groups.

Reading Tuberculin Skin Test

What it looks like if you have TB after the shot?

If you have TB in your body, a firm red bump will form at the shot site within 2 days. If the test shows that you are infected with TB (positive), your doctor probably will order more tests. A TB-positive skin test can't tell when you became infected with TB.

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

Within 48 to 72 hours, a positive TB skin test is marked by an area of reddish induration greater than 10 mm. It is the induration (firm bump) that is gently palpated that determines the size, not the area of redness. This reaction is slightly larger than the average positive test 17 mm in size.

What is positive in PPD skin test?

The positive skin reaction in the PPD test can occur in:

Active TB infection. TB exposure in the past (latent TB infection) BCG vaccination in the past (live attenuated mycobacterial strain) Infection with a variety of non-tuberculosis Mycobacteria.

What size is a positive TB skin test?

* For employees who are otherwise at low risk for TB and who are tested as part of an infection control screening program at the start of employment, a reaction of 15 mm is considered positive.

Is tuberculosis a STD?

TB is not spread through sexual intercourse or kissing or other touch. TB bacteria are spread through the air from one person to another. When a person who has TB disease of the lungs or throat coughs, speaks, or sings, TB bacteria are spread in the air.

What color is a positive TB test?

Results. A tuberculin skin test is done to see if you have ever had tuberculosis (TB) (infection with Mycobacterium tuberculosis). 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.

Can you have TB and not know it?

A person with latent, or inactive, TB will have no symptoms. You may still have a TB infection, but the bacteria in your body is not yet causing harm. Symptoms of active TB include: A cough that lasts more than three weeks.

What is normal PPD reading?

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.

How do I know my skin test results?

You'll feel a little prick when the substances are placed under your skin. After 15 minutes or so, the doctor will look for signs that you're having a reaction. Usually your skin will get red or swollen if you're allergic to something in the test.

What will a negative skin test result show?

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.

Can TB be cured?

The vast majority of TB cases can be cured when medicines are provided and taken properly.

How do you treat a positive TB test?

As of 2018, there are four CDC-recommended treatment regimens for latent TB infection that use isoniazid (INH), rifapentine (RPT), and/or rifampin (RIF). All the regimens are effective. Healthcare providers should prescribe the more convenient shorter regimens, when possible.

Will a positive PPD always be positive?

Did you know? Once you have a positive TB skin test you will always have a positive TB skin test, even if you complete treatment. Ask your doctor for a written record of your positive skin test result.

What does a PPD reaction look like?

The skin exposed to the PPD may become red, swollen, blistered, dry, thickened and cracked. You may feel a burning or stinging sensation. Symptoms will usually appear within 48 hours, although strong irritants may cause your skin to react immediately.

What does tuberculosis look like on the skin?

The skin lesions are usually solitary and manifest as painless, violaceous or brown–red, indurated warty plaques that range from 1 to 5 cm in diameter. Although ulceration is uncommon, fissures that exude purulent drainage or keratinous material may occur.

How long is a negative TB skin test good for?

to be repeated? If you have a negative skin test, you need a repeat test at least once every four years. If you have a documented positive skin test, you must have an initial chest X-ray. After that, you still need to be screened every four years.

Does redness mean a positive TB test?

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.

Can I get TB if I am vaccinated?

The BCG vaccine is not very good at protecting adults against TB. You can still get TB infection or TB disease even if you were vaccinated with BCG. You will need a TB test to see if you have latent TB infection or TB disease.

What not to do before TB test?

You don't any special preparations for TB skin test or a TB blood test.