Tb skin test how to read results

tb skin test how to read results

How is the TST Read? The skin test reaction should be read between 48 and 72 hours after administration by a health care worker trained to read TST results. A patient who does not return within 72 hours will need to be rescheduled for another skin test. The reaction should be measured in millimeters of the induration (firm swelling). Sep 11, "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 hours after the injection when the size of the induration is maximal.

The Mantoux tuberculin skin test TST is one method of determining whether a person is infected with Mycobacterium tuberculosis. Reliable administration and reading of the TST requires standardization tezt procedures, training, supervision, and practice.

The TST is performed rsad injecting 0. The injection should be made with a tuberculin syringe, with the needle bevel tb skin test how to read results what does c3 mean in shoe size. The TST is an intradermal injection.

When placed correctly, the sskin should produce a pale elevation of the skin a wheal 6 to 10 mm in diameter. The skin test reaction should be hw between 48 and 72 hours after administration by a health care worker trained to read TST results.

A patient who does not return within 72 hours will need to be rescheduled for another skin test. The reaction should be measured in millimeters of the induration firm swelling. The reader should not measure erythema redness.

The diameter of the indurated area should be measured across the forearm perpendicular to the long axis. Some persons may react to the TST even though they are not infected with M. The causes of how to get qualification certificates false-positive reactions may include, but are not limited to, the following:.

A TB blood test is the preferred method of testing for people who have received the BCG vaccine in order to prevent false-positive reactions. Some persons may not react to the TST even though they are infected with M.

The reasons for these false-negative reactions may include, but are not limited to, the following:. Most persons can receive a TST. TST is the recommended method of testing what month does spring break start children younger than 5 years of age.

TST is contraindicated only for persons who have had a severe reaction e. It is not contraindicated for any other persons, including infants, children, pregnant women, or persons living with HIV. In general, there is no risk associated with repeated tuberculin skin test placements. If a person does not return within hours for a tuberculin skin test reading, a second hoa can be placed as soon as possible.

A boosted resulst occurs mainly in previously infected, older adults whose ability to react to tuberculin has decreased over time. When given a TST years after infection, these persons may have an initial negative reaction.

However, the TST may stimulate the immune system, causing a positive or boosted reaction to subsequent tests. Tb skin test how to read results with live viruses, including measles, mumps, rubella, oral polio, varicella, yellow fever, BCG, and oral typhoid, may interfere with TST reactions.

For persons scheduled to receive a TST, testing should be done as follows:. There are two kinds of tests that are used to determine if a person has been infected with TB bacteria: the TB blood test and the TB skin test. The tests measure the response of TB proteins when they are mixed with a small amount eead blood. Only one visit is required to draw blood for this test.

Health care providers are encouraged to use newer TB blood tests to screen for TB infection. In order to prevent false-positive reactions, TB blood tests are also the preferred ro of TB testing for people 5 years of age and older who rread received the BCG TB vaccine. A diagnosis of latent TB infection is made if a person has a positive TB test result and a medical evaluation does not indicate TB disease.

TB disease is diagnosed by medical history, physical examination, chest x-ray, and other laboratory tests. TB disease is treated by taking several drugs as recommended by a health care provider. There are several treatment regimens for the treatment of latent TB infection. These regimens use the drugs isoniazid, rifapentine, or rifampin. Short-course regimens include: Three months of reslts isoniazid plus rifapentine 3HPfour months of daily rifampin 4Ror three months of daily isoniazid plus rifampin 3HR.

Short-course latent TB infection treatments are effective, are safe, and have higher completion rates than longer treatments. If a short-course treatment regimen is not an option, 6H or 9H is an effective alternative latent TB infection treatment regimen.

Skip how to become a scopist to site content Skip directly to page options Skip directly to A-Z link. Tuberculosis TB. Section Navigation. Facebook Twitter LinkedIn Syndicate. Fact Sheets. Minus Related Pages. Open All Close All. What is it? How is the TST Administered? How is the TST Read? What Are False-Positive Reactions? What Are False-Negative Reactions? The reasons for these false-negative reactions may include, but are not limited to, the following: Anergy Recent TB infection within the past 8 to 10 weeks Very young age younger than 6 months Recent live-virus measles or smallpox vaccination Incorrect method of giving the TST Incorrect measuring or interpretation of TST reaction.

What is a Boosted Reaction? Why is Two-Step Testing Conducted? For persons scheduled to receive a TST, testing should be done as follows: Either on the same day as vaccination with live-virus vaccine or At least 1 month after the administration of the live-virus vaccine. Are there alternative tests to the TST? Diagnosis of TB Disease TB disease is diagnosed by medical history, physical examination, chest x-ray, and other laboratory tests.

What are treatment options for latent TB infection? Additional Information. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care settings, MMWR ; 54 No.

Targeted tuberculin testing and treatment of latent tuberculosis infection pdf icon. MMWR ; 49 No. Lewinsohn et al. To receive email updates about this page, enter your email address: Email Address. What's this? Links with this icon indicate that you are leaving the CDC website. Linking to ersults non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.

You will be subject to the destination website's privacy policy when you follow the link. CDC is not responsible for Section compliance accessibility on other federal or private website. Cancel What can i take to help with anxiety. An induration of 5 or more millimeters is considered positive in -People living with HIV -A recent contact of a person with infectious TB disease People with chest x-ray findings suggestive of previous TB disease -People with organ transplants -Other immunosuppressed people e.

An induration of 10 or more millimeters is considered positive in -People born in countries where TB disease is common, including Mexico, the Philippines, Vietnam, India, China, Haiti, and Guatemala, or other countries with high rates of TB -People who abuse drugs -Mycobacteriology laboratory workers -People who live or work in high-risk congregate settings e. An induration of 15 or more millimeters is considered positive in -People with no known risk factors for TB.

Tuberculin Skin Testing

Last Updated: March 25, References Approved. This article was medically reviewed by Mandolin S. Ziadie, MD. This article has been viewed , times. A tuberculosis skin test is also known as the Mantoux tuberculin test. This test measures your immune system's response to the bacteria that causes tuberculosis. Your results will be interpreted by your doctor a couple of days after the test.

If you're curious about how to read a tuberculosis skin test, this article will guide you through the process, but remember: the test must be read by a trained professional. To read a tuberculosis skin test, start by going to the doctor for a test, which involves an injection that will cause a welt on your arm.

If the welt is a soft bump, the results are likely negative. However, if it's a hard, dense, raised formation, the results may be positive. Regardless of your results, make sure to return to your doctor within 48 to 72 hours after the initial injection to have your results interpreted. To tell whether you have TB by measuring your welt, keep reading!

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No account yet? Create an account. Edit this Article. We use cookies to make wikiHow great. By using our site, you agree to our cookie policy. Cookie Settings. Learn why people trust wikiHow. Download Article Explore this Article parts. Tips and Warnings. Related Articles. Article Summary. Medically reviewed by Mandolin S. Part 1 of Go to your doctor for the tuberculosis skin test. You will be given an injection of a purified protein derivative into the inner forearm that will result in a mm welt that will disappear within a few hours.

Leave your arm uncovered. Do not place a bandage over the site of the test for the required 48 to 72 hours. You can wash and dry your arm carefully. This can cause redness or swelling that may cause the results to be misread. You can apply a cold washcloth on your arm if it is itchy. Return to your doctor. The test must be read within hours. If you do not come back within 72 hours, the test is considered invalid and will have to be repeated. Find and mark the induration. Use your fingertips to find the induration.

This is a hard, dense, raised formation with definite borders. If there is a firm bump, use a pen to mark the widest edges of the induration on the forearm. The reddened area or any slight swelling does not count towards the size of the induration. You cannot always see the induration. You must find the induration with your fingertips. Measure the induration. The test site may be red, but that does not mean you have TB. You have to measure the induration. This induration is measured across your forearm in millimeters.

Place the edge of the ruler with "0" on the left edge of the raised bump where you marked it with a pen. Look where the mark made on the right side of the bump falls on the ruler.

Part 2 of Determine if the individual is in the high-risk group. An induration of 5mm or more is categorized as positive in individuals in the high-risk group.

This group includes people who have: HIV received organ transplants been immunosuppressed for various reasons recent contact with a TB positive person chest x-ray consistent with old healed TB end stages of renal kidney disease [9] X Trustworthy Source PubMed Central Journal archive from the U. National Institutes of Health Go to source. Determine if the individual is in the moderate-risk group. An induration of 10mm or more is categorized as positive in people in the moderate-risk group.

This includes people who: immigrated recently from a country with widespread TB use injection drugs work in healthcare settings, prisons, nursing homes, or other similar areas have clinical conditions that put them at risk, like diabetes, leukemia, low body weight are children under age 4 are children and adolescents exposed to high-risk adults [10] X Trustworthy Source Centers for Disease Control and Prevention Main public health institute for the US, run by the Dept.

Look for a large induration for everyone else. For those not in the high or moderate-risk group, an induration of 15mm or more is considered positive. This includes all individuals, regardless of any risk factors they might have. The test is also considered positive if there are blisters present, even if there is little swelling. Look for a negative result.

If there is no firm bump, the result is negative. Even if you believe your skin test is negative, you must return to the doctor to have it professionally read. Did you know you can read expert answers for this article?

Unlock expert answers by supporting wikiHow. Mandolin S. Support wikiHow by unlocking this expert answer. Not Helpful 17 Helpful Not Helpful 45 Helpful Include your email address to get a message when this question is answered. Go to any further testing your doctor might order if the test is positive or if the test is considered borderline positive.

Helpful 0 Not Helpful 0. False positives and false negatives can happen with this test. If there are any questions about your tuberculosis test results, consult with your doctor as soon as possible. Helpful 61 Not Helpful A TB test should always be interpreted by a trained health professional within the 72 hour time span. These professionals receive training and practice to measure the results correctly. Helpful 47 Not Helpful Related wikiHows How to.

How to. More References 3. About This Article. Medically reviewed by:. Co-authors: Updated: March 25, Categories: Tuberculosis.

Article Summary X To read a tuberculosis skin test, start by going to the doctor for a test, which involves an injection that will cause a welt on your arm. Italiano: Leggere un Test Cutaneo per la Tubercolosi. Nederlands: Een huidtest voor tuberculose aflezen. Thanks to all authors for creating a page that has been read , times.

It is wider and bruising slightly. The article explained what I should be concerned about and all is well for the time being. More reader stories Hide reader stories. Did this article help you?

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