Tuberculin Skin Test

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IN THE NAME OF ALLAH THE MOST GRACIOUS,THE MOST MERCIFUL

TUBERCULIN SKIN TESTING : 

TUBERCULIN SKIN TESTING

QUESTION NO.3 : 

QUESTION NO.3 TUBERCULIN SKIN TESTING THERE ARE MORE THAN ONE METHOD FOR THIS TEST,BUT THE MANTOUX METHOD IS MOST ACCURATE AND WIDELY USED. USED ALSO TO DIFFERENTIATE PULMONARY FROM EXTRA-PULMONARY TUBERCULOSIS. TUBERCULIN IS USED TO ASSESS THE INDIVIDUAL`S IMMUNOLOGIC REACTION AGAINST TUBERCLE BACILLI. MORE USEFUL IN ADULTS THAN IN CHILDREN. ALL CONTACTS OF SMEAR POSITIVE PULM;TB CASES SHOULD HAVE TUBERCULIN SKIN TESTING.

Latent TB infection : 

Latent TB infection A PERSON WITH LATENT TB INFECTION: Has a POSITIVE skin test. Has a NORMAL chest x-ray.

Latent TB infection : 

Latent TB infection Has breathed in TB germs. Feels fine, is not sick. Cannot spread TB germs to others.

Tests for latent tuberculosis : 

There are currently two major classes of tests used to identify patients with latent tuberculosis: tuberculin skin tests and γ-interferon tests. The tuberculin skin tests in use include Mantoux test Heaf test Tine test γ-interferon tests There are currently two available ELISPOT QuantiFERON-TB Tests for latent tuberculosis

TST : 

TST All testing activities should be accompanied by a plan for follow-up care

TINE TEST : 

The Tine test is a multiple puncture tuberculin skin test This test uses a small "button" that has four to six short needles coated with TB antigens (tuberculin). The needles are pressed into the skin (usually on the inner side of the forearm), forcing the antigens into skin. The test is read by measuring the size of the largest papule. A negative result is the presence of no papules. Because it is not possible to control precisely the amount of tuberculin used in the tine test, a positive test should be verified using the Mantoux test. For this reason, the tine test is not as widely used as the Mantoux test and is considered to be less reliable. It is not recommended for use by the American Thoracic Society or Centers for Disease Control and Prevention (CDC). Mono-vacc Test (O.T.), Aplitest, and the Tine test are names of multiple tine tuberculin skin tests. TINE TEST

TINE TEST kit: : 

TINE TEST kit:

HEAF TEST : 

The test is named after F. R. G. Heaf. Until 2005, the test was used in the United Kingdom to determine if the BCG vaccine was needed; the Mantoux test is now used instead. The Heaf test was preferred in the UK, because it was felt that the Heaf test was easier to interpret, with less inter-observer variability, and that less training was required to administer and to read the test. The test was withdrawn because manufacturers could not be found for tuberculin or for Heaf guns. The Heaf test may be informally referred to as the six pricks, as it gives six individual injections. HEAF TEST

HEAF TESTProcedure : 

A Heaf gun is used to inject multiple samples of testing serum under the skin at once. A Heaf gun with disposable single-use heads is recommended. The gun injects purified protein derivative equivalent to 100,000 units per ml to the skin over the flexor surface of the left forearm in a circular pattern of six. The test is read between 2 and 7 days later. The injection must not be into sites containing superficial veins. HEAF TESTProcedure

HEAF TESTFrederick Heaf, David Davies Professor of Tuberculosis at Llandough Hospital, : 

HEAF TESTFrederick Heaf, David Davies Professor of Tuberculosis at Llandough Hospital,

HEAF TESTREADING : 

The reading of the Heaf test is defined by a scale: Negative - No induration, maybe 6 minute puncture scars Grade 1 - 4-6 papules (also considered negative) Grade 2 - Confluent papules form indurated ring (positive) Grade 3 - Central filling to form disc (positive) Grade 4 - Disc >10 mm with or without blistering (strongly positive) Grades 1 and 2 may be the result of previous BCG or avian tuberculosis. Patients who have a grade 3 or 4 reaction require X-ray and follow-up. HEAF TESTREADING

Interferon-gamma determination (QuantiFERON® Tests) : 

Interferon-gamma determination (QuantiFERON® Tests)

Interferon-gamma determination : 

Whole-blood test used to detect M. tuberculosis infection Entails mixing blood samples with antigens from M. tuberculosis, M. avium complex, and controls and incubating for 16 to 24 hours T cells of sensitized individuals produce ifn-γ when they re-encounter the antigens of m. Tuberculosis. Test measures and compares amount of interferon-gamma (ifn-) released by blood cells in response to antigens. Interferon-gamma determination

Comparison of QFT and TST : 

QFT In vitro test Specific antigens No boosting 1 patient visit Minimal inter-reader variability Results possible in 1 day Requires phlebotomy TST In vivo test Single antigen Boosting 2 patient visits Inter-reader variability Results in 2-3 days Comparison of QFT and TST

Tuberculin skin tests : 

Tuberculin skin tests Tine test Heaf test MANTOUX TEST

TSTINDICATIONS : 

TST has been used to identify patients actively infected with TB To measure the prevalence of infection in a community To select susceptible or high-risk patients for BCG vaccination. The test has been in existence for more than 100 years Has remained more or less unchanged for the last 60 years TSTINDICATIONS

TEST LIMITATIONS : 

SENSITIVITY AND SPECIFICITY VARY DEPENDING ON THE POPULATION TESTED AND REACTION CUT-OFF POINTS. REQUIRES FOLLOW-UP VISITS. ABOUT 25% CONFOUNDED BY HIV,BCG,MOTT. FALSE NEGATIVE RATES CAN OCCUR IN UPTO 50% OF THOSE WITH ADVANCED HIV INFECTION. ABOUT 25% OF THOSE WITH ACTIVE TB MAY HAVE NEGATIVE TST. TEST LIMITATIONS

WHAT IS TUBERCULIN? : 

TUBERCULIN IS A BROTH CULTURE FILTRATE OF TUBERCLE BACILLI. FIRST PREPARED BY ROBERT KOCH IN 1880 IT WAS WRONGLY PROMOTED AS CURE FOR TUBERCULOSIS. The tuberculin test is based on the fact that infection with M. tuberculosis produces a delayed-type hypersensitivity reaction to certain antigenic components of the organism that are contained in extracts of culture filtrates called "tuberculins WHAT IS TUBERCULIN?

EVOLUTION OF TUBERCULINS : 

OLD TUBERCULIN PPD PPD-S PPD-RT23 PPD-WEYBRIDGE PPD-TWEEN 80 EVOLUTION OF TUBERCULINS 1880-1930 1934 1 1891.ROBERT KOCH 1932. SEIBERT & MUNDAY 1941. SEIBERT & GLENN 1941. WHO & UNICEF

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HOW PPD IS MADE?

Storage and handling of PPD : 

Date and initial when vial is opened Discard 30 days after opening It is sensitive to light, keep out of light Draw up just prior to injection Store at 35 to 46 degrees F° in a refrigerator or cooler with ice packs Storage and handling of PPD

How is the Mantoux skin test given? : 

Health worker uses a needle and syringe Inject 0.1 ml of 2 tuberculin units of liquid tuberculin (PPD RT23) between the layers of the skin (intradermally) Usually on the forearm (volar surface) Disposible syringes of 1 ml capacity with scale of 0.01 ml and 25-26mm gauges should be used How is the Mantoux skin test given?

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1 ml disposable syringe with 25-26mm gauges 0.1ml tuberculin is filled

Applying the tuberculin skin test : 

Applying the tuberculin skin test Inject 0.1 ml of 2 TU PPD tuberculin solution intradermally on volar surface of lower arm using a 25-26 gauge needle

Applying the tuberculin skin test : 

Applying the tuberculin skin test

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Giving the Mantoux tuberculin skin test

Applying the tuberculin skin test : 

Applying the tuberculin skin test Produce a wheal 6 to 10 mm in diameter

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Slightly pull down the skin in the direction of the needle and parallel to forearm

TST: infection control reminders : 

Needles should not be recapped, bent, broken, or removed from syringes. Safety devices to prevent needle stick injuries are recommended. Gloves are not necessary for administering intradermal injections (however, individual institution or agency policies may vary). TST: infection control reminders

How is the skin test read? : 

Test is read by a trained health worker 48 - 72 hours after the tuberculin injection Diameter of the indurated (swelling) area is measured across the forearm Erythema (redness) is not measured Test result is measured in millimeters (mm) How is the skin test read?

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Only the induration is being measured. This is CORRECT. Measure reaction in 48 to 72 hours Measure induration, not erythema Record reaction in millimeters, not “negative” or “positive” Ensure trained health care professional measures and interprets the TST result

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The erythema is being measured. This is INCORRECT.

Reading the tuberculin skin test : 

Read 2-3 days after placing the test Feel for induration Color change without induration is not included in the measurement Use a ruler or calipers Have someone else check if unsure Always document the exact size (mm) – not just “positive” or “negative” Reading the tuberculin skin test

Reading the TST (2) : 

Reading the TST (2) Educate patient and family regarding significance of a positive TST result Positive TST reactions can be measured accurately for up to 7 days Negative reactions can be read accurately for only 72 hours

How is the skin test classified? : 

Whether a reaction to the Mantoux tuberculin skin test is classified as positive depends on the size of the induration (swelling) and the person’s risk factors for TB How is the skin test classified?

TST Interpretation (1) : 

5-mm induration is interpreted as positive in HIV-infected persons OR persons with risk factors for HIV and unknown HIV status. Close contacts to an infectious TB case Persons with chest radiographs consistent with old healed tuberculosis. TST Interpretation (1)

TST Interpretation (2) : 

10-mm induration is interpreted as positive in (cont.) Organ transplant recipients Other immunosuppressed patients (e.g., those taking the equivalent of >15 mg/d of prednisone for 1 month or those taking TNF-α antagonists) TST Interpretation (2)

TST Interpretation (3) : 

10-mm induration is interpreted as positive in Recent immigrants from TB endemic areas Injection drug users Residents or employees of congregate settings Mycobacteriology laboratory personnel TST Interpretation (3)

TST Interpretation (4) : 

10-mm induration is interpreted as positive in (cont.) Persons with clinical conditions that place them at high risk Children < 4 years; infants, children, and adolescents exposed to adults at high-risk TST Interpretation (4)

TST Interpretation (5) : 

Persons with no known risk factors for TB. TST Interpretation (5) 15-mm induration is interpreted as positive in ____________________________________________________

Factors that May Cause False-Positive and False-Negative Reactions to the Tuberculin Skin Test : 

Type of Reaction Possible Cause False-positive Nontuberculous mycobacteriaBCG vaccination False-negative AnergyRecent TB infectionVery young age: < 8 mos. oldLive-virus vaccinationOverwhelming TB disease Factors that May Cause False-Positive and False-Negative Reactions to the Tuberculin Skin Test Technique Improper storage Adsorption Improper administration (too deep, too little antigen) Failure to detect/interpret induration

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Anergy Do not rule out diagnosis based on negative skin test result Consider anergy in persons with no reaction if HIV infected Overwhelming TB disease Severe or febrile illness Viral infections Live-virus vaccinations Immunosuppressive therapy.

Boosting : 

Some people with LTBI may have negative skin test reaction when tested years after infection Initial skin test may stimulate (boost) ability to react to tuberculin Positive reactions to subsequent tests may be misinterpreted as a new infection Boosting

Two Step Testing : 

Two Step Testing Use two step testing for initial skin testing of adults who will be retested periodically If first test positive, consider the person infected If first test negative, give second test 1-3 weeks later If second test positive, consider person infected If second test negative, consider person uninfected

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Two-step Testing Baseline PPD test PPD = 00 mm (negative results) Repeat PPD 1 - 3 weeks later PPD < 10 mm RESULTS: person probably does NOT have TB infection POSITIVE PPD > 10 mm RESULTS: this is a “boosted” reaction due to TB infection a long time ago

Tuberculin reactor or tuberculin converter? : 

Converter An individual whose tuberculin skin test (PPD) reaction has been documented to change from negative to positive (or to increase by 10 mm or more) during the previous two years Reactor An individual with a positive tuberculin skin test reaction Tuberculin reactor or tuberculin converter?

Common myths : 

Myth: “My doctor says I’m allergic to TB skin tests and should not take them” Fact: repeated TB skin tests do not sensitize or make people “allergic” to tuberculin Common myths

Common myths (2) : 

Myth: “I used to have a positive TB test, but now I’m negative” Fact: past positive PPD is considered TB infection – Later negative tests maybe due to: t inaccurate multi-puncture test t decreased immune response t should have 2-step test (PPD) Common myths (2)

UNDESIRABLE EFFECTS : 

Adverse reactions are seldom encountered transient burning sensation may be experienced immediately after the injection, and pain, irritation or discomfort may rarely occur In individuals who are extremely sensitive to tuberculin, vesicles, bullae or ulceration may appear at the injection site, and fever or lymph node swelling UNDESIRABLE EFFECTS

Contra-indications? : 

No contraindications to an initial test Extreme caution should, however, be exercised for individuals who have had previous severe skin reaction to any tuberculin product Testing with TUBERCULIN PPD RT 23 SSI may be performed during pregnancy and lactation Contra-indications?

UNDESIRABLE EFFECTS : 

Adverse reactions are seldom encountered transient burning sensation may be experienced immediately after the injection, and pain, irritation or discomfort may rarely occur In individuals who are extremely sensitive to tuberculin, vesicles, bullae or ulceration may appear at the injection site, and fever or lymph node swelling UNDESIRABLE EFFECTS

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SUMMARY

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TUBERCULIN TEST POSITIVE NEGATIVE Repeat after 6-8 weeks Negative BCG follow-up INH for lactating Positive Clinical+ CXR+ sputum Evidence of TB Treat TB NO Evidence of TB Age <15 y INH >15 y Follow-up Clinical+ CXR+ sputum Evidence of TB Treat TB NO Evidence of TB Age <15 y INH >15 y Follow-up MANAGEMENT FOR CONTACTS OF TB + CASES

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THE END

POST-SESSION : 

POST-SESSION

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THANK YOU AND HAVE A TB-FREE LIFE