Presentation on theme: "VDH TB Control and Prevention Program"— Presentation transcript:
1 VDH TB Control and Prevention Program The TB Risk AssessmentVDH TB Control and Prevention Program2011
2 Why do a TB risk assessment? Identify those in need of further testing for TB diseaseMeet job or program requirementsIdentify those who would benefit from treatment for latent TB infection, thus preventing TB disease
3 Persons at Risk for Developing TB Disease Persons at high risk for developing TB disease fall into 2 categories:Those who have been recently infectedThose with clinical conditions that increase their risk of progressing from LTBI to TB diseaseThis is assuming that the screening for TB symptoms is negative. If not, the clinician should begin the diagnostic process discussed in the first presentation. However, if the patient has no symptoms, the TB risk assessment will provide a guide to how to proceed.Take out the TB Risk Assessment in your folder and follow along.
4 Recent Infection as a Risk Factor Close contacts to person with infectious TBSkin test or IGRA converters (within past 2 years)Recent immigrants from TB-endemic regions of the world (within 5 years of arrival to the U.S.)Children ≤ 5 years with a positive TSTResidents and employees of high-risk congregate settings (e.g., correctional facilities, homeless shelters, health care facilities)This is section II.A on the TB Risk Assessment.
5 Increased Risk for Progression to TB Disease A history of prior, untreated TB or fibrotic lesions on chest radiograph suggestive of past TBUnderweight or malnourished personsInjection drug usersThose receiving TNF-α antagonists for treatment of rheumatoid arthritis or Crohn’s diseasePersons with certain medical conditions such asHIV, DM, CRF/dialysis, silicosis, organ transplant,CA of head/neck, gastrectomy or jejunoilial bypassThis is section II.B on the TB Risk Assessment.
6 TB Screening or TB Testing For more than a decade it has been recognized that the TST is less sensitive in low risk populationsTB Screening, where a patient is asked a variety of questions by a health care provider, is a more sensitive way to identify who needs further testing. Ask about:SymptomsRisk for acquiring TB infectionRisk for progressing to TB disease if infectedIt is recommended that only those at higher risk for either TB infection or progression to TB disease be tested. This is to increase the likelihood that those positive on a TST (or IGRA) are actually truly positive, and not false positives.For a complete discussion of the recommendations for testing, see “Targeted Tuberculin Testing and Treatment of Latent Tuberculosis Infection,” June 9, 2000 from the CDC. The TB Risk Assessment should be completed, during an interview with the client, by a physician or public health nurse.
7 Occupations Where TB Screening is Acceptable Assisted living employeesFoster care parentsDay care employeesSchool employeesResidential school attendees*TST or IGRA is indicated if there is a risk factor on the risk screenA chest x-ray is indicated for positive TST or IGRAA full diagnostic work-up is needed if symptoms consistent with TB
8 Who can sign the “free from TB” statement? PhysicianPublic Health Nurse or ClinicianPhysician’s Assistant or Nurse Practitioner if for Adult Day CareFor those with negative TB risk assessments, and who do not work in settings requiring a TST or IGRA, a statement of TB screening stating the person if free from TB in communicable form is sufficient.There are forms that can be used for TB screening on the TB website, and there are samples in your folders.Remember, in the context of TB screening, a decision to test with a TST is a decision to treat LTBI if the test is positive.TST and IGRA testing should be offered to those with any risk identified for infection or disease.
9 Who needs the TST or IGRA? (regardless of risk screening) Health care workersStudents preparing for health care careersAdult day care participantsAnyone who will be serially tested with TST or IGRAAll persons before taking any TNFα antagonist drugs(Remicade, Humira, Enbrel, Kineret, Rituxan, etc.)Adult day care participants, until the regulations are changed. The department of social services realizes the inconsistency in this requirement.Some settings that are not required to have TSTs (ex. some assisted living sites) still prefer to have a baseline on record in case a case of TB needs follow-up in their facility.The tumor necrosis factor alpha antagonist drugs all have an increased risk of those with LTBI progressing to TB disease. These drugs are used to treat rheumatoid arthritis, Crohn’s disease, and psoriasis. As new applications are found, new groups of physician’s offices will need to be aware of the TB risk associated with this class of drugs.
10 Diagnosis of TB Infection: Mantoux TB Skin Test (TST) One way to evaluate for TB infectionIs the preferred type of skin test (vs. tine or multi-puncture tests)Is useful in:Screening people for TB infection (contacts and targeted testing)Examining those with symptoms of TB diseaseThe other way is the IGRA blood test that we will talk about in the next section.
12 The tuberculin skin testing (TST) In use for more than 100 years (1890)0.1 ml of 5 tuberculin units of purified protein derivative (PPD) administered intradermallyEvaluated (read) 48 to 72 hours after administrationCross reacts with other mycobacteria, including BCG vaccineA history of BCG vaccine is not a contraindication
13 TST Result: False Positive Possible causesNon-tuberculous mycobacteriaBCG vaccinationRoutinely administered to children in countries where TB is prevalentNot a contraindication for the administration of the TB skin testWanes over time ; if TST is + likelydue to TB infection if risk factors present
14 TST Result: False-Negative Causes includeAnergy / immune suppressionRecent TB infection (within past 10 weeks)Very young age (younger than 6 months old)Incorrect administration and storage of test solutionLive-virus vaccination within 4-6 weeksOverwhelming TB DiseasePoor TST administration techniqueAnergy is the inability to react to skin tests because of a weakened immune system. Many conditions, such as HIV infection, cancer, or severe TB disease itself, can weaken the immune system and cause anergy. HIV infection is a main cause of anergy or immunosuppression.ANGERY TESTING IS NO LONGER RECOMMENDED EVEN IN HIV + PERSONSRecent TB infection:It takes 2 to 10 weeks after TB infection for the body’s immune system to be able to react to tuberculin. Therefore, after TB has been transmitted, it takes 2 to 10 weeks before TB infection can be detected by the tuberculin skin test. For this reason, close contacts of someone with infectious TB disease who have a negative reaction to the tuberculin skin test should be retested 10 weeks after the last time they were in contact with the person who has TB diseaseVery Young Age:Because their immune systems are not yet fully developed, children younger than 6 months old may have a false-negative reaction to the tuberculin skin test
15 Administering Mantoux TST Ask about any history of previous positive TSTInject 0.1 ml of 5 tuberculin units of liquid tuberculin, intradermally, using a 27 gauge needle with bevel upUse the volar surface of forearm when possibleMay use the scapular area if forearmProduce a wheal 6 to 10 mm in diameterAdvise no creams, band-aids, scratchingMay shower or swimRecord the site, lot number, date and time of administration, and person giving the testWe are going to view a much more detailed video, but as an overview: [review the slide]A person with a previous positive should only be retested if documentation is lacking and is needed. An IGRA might be preferable.A tuberculin unit is a standard strength of tuberculinMost people with TB infection have a positive reaction to the tuberculinThe scapular area on the back can be used if the forearm can not be used due to history of bilateral mastectomy, rash, or extensive tattoos.
16 Reading the Mantoux TST Examine the patient’s arm hours after the tuberculin is injectedAssess the injection site for erythema (redness) and induration (swelling that can be felt) by lightly palpating the areaMeasure the diameter the indurated (raised area only, across the forearm, recording in millimeters (do not measure the erythema)Record the date, time, size of induration in millimeters, interpretation (positive or negative), and follow-up recommendedIf difficult to assess, try wetting with alcohol, moving a pen in from each side to feel resistance, flexing the hand, pronating the arm to move underlying structures, or observing across the area against a different color background. It takes a very light touch.
17 Interpreting the TST Results Interpretation takes into account the patient’s individual risk factors for TB infection and progression to diseaseCut points for positivity are at 5, 10, and 15 mmIt is necessary to know the patient’s history (TB risk assessment) to determine an individual patient’s TST interpretation
18 Interpretation of the TST: Persons Positive at > 5 mm People with HIV infectionClose contacts of people with infectious TBPersons with fibrotic chest x-ray findings suggestive of prior TB diseasePatients with organ transplantsPersons immunosuppressed for other reasons(on TNF-a drugs, or the equivalent of >15 mg/day of prednisone for 1 mo. or longer)Refer to the CDC fact sheet in the participant folders.TNF-a drugs = Remidaide, Humaria, Enbrel etc. for Rheumatoid Arthritis, Crohn’s Disease, psoriasis.
19 Interpretation of the TST: Persons Positive at > 10 mm Recent immigrants (< 5 years)Injection drug usersResidents and employees of high-risk congregate settingsMycobacteriology laboratory personnelPeople with clinical conditions that place them at high risk (those listed on risk screen)Children < 4 years oldInfants, children and adolescents exposed to adults in high-risk groupsPersons who have lived in high risk countries for 3 months or more, in contact with the local population.
20 Interpretation of the TST: Persons Positive at > 15 mm An induration of 15 or more millimeters is considered positive in any person, including persons with no known risk factors for TB.Targeted skin testing programs should only be conducted among high-risk groups.
21 Reading the TSTEducate patient and family regarding significance of a positive TST resultPositive TST reactions can be measured up to 7 days after administrationNegative reactions must be read between hours after administrationSignificance = have breathed in the germ that can cause TB in the future. Need evaluation to rule out TB disease. If ruled out, can take medication to treat the TB infection and reduce the risk of progression to TB disease.Introduce the “Stop TB” handout.Explain the difference between TB infection and TB disease to the patient, and the need for a chest x-ray.Promote taking isoniazid for treatment of LTBI to reduce the risk of TB disease in the future.
22 Other Issues in Skin Testing Booster Phenomenaability to react to tuberculin may wane with timea TST may prompt new antibody productiona second TST detects this “boosted,” increased responseTwo-step testing – two TSTs, 1 to 3 weeks apartUse with groups who will have repeated TSTs as part of infection control programsAvoids a “boosted” test classified as new positive, which could reflect undetected transmissionTwo step testing is indicated for anyone who will be serially tested, especially health care workers. If two test testing is not done on hire, and the next TST (1 year later) is positive, there will be no way to determine if recent transmission has occurred. The “positive” would be considered a TST conversion, go on the OSHA 300 log, and would need to be investigated.Two step Testing ..if first test is neg, repeat test in 1 to 3 weeks If the second test is neg…they are negIf person being tested has had a TST within the past year, you can use that as #1 and just do the #2 test as long as you can get documentation of the #1 TST.If #1 test is – and #2 test is + you have boosted old infection and if the person has not been previously treated, do CXR, R/O TB and offer TX for LTBI.
23 Interferon Gamma Release Assay – the TB blood testor IGRA
24 Basic Principles of IGRA testing Peripheral blood lymphocytes from a person suspected of having tuberculosis infection are exposed to antigens (different from those in PPD/more specific) from Mycobacterium tuberculosisIf person has been infected with M. tuberculosis, lymphocytes will respond by producing IFN-γThe tests measure the total IFN-γ produced (QFT-GIT) or number of cells that produce IFN-γ (T.Spot TB)
25 Interferon Gamma Release Assays – The TB blood tests An equally acceptable choice for TB infection testingPreferred for those with Hx of BCG vaccination – no cross reactivity with BCG vaccineDo cross react with a few NTMsMay be preferred for those who are not likely to return for TST reading (SA, homeless, etc.)Two types of tests approved by the FDAQuantiFERON TB Gold-in-Tube or QFT-GITT-Spot TBResults are both quantitative and qualitativeCross react with M. kansasii, M. szulgai, M. marinum, and M. riyadhense.Both the qualitative “positive”, “negative” or “indeterminant” AND the numerical values are needed to completely understand the results in come cases.
27 T Spot Sample Result Positive - Nil ≤ 10 spots TB Antigen ≥ 8 spots Mitogen - Any ResponseNegative - Nil ≤ 10 spotsTB Antigen ≤ 4 spotsBorderline 5,6, or 7 spotsTable 3 Interpretation Criteria for T.Spot TB, CDC Guidelines, pg. 16
28 Comparison of IGRA vs. TST One visitNo cross reaction with BCGLimited time frame from draw to incubation in labMore expensive than TSTLess subjective determination of resultsNot approved for children under age 5 yearsTwo visits (4 for two-step test)Cross reacts with BCG with potential for false positivesTime frame constraint for readingLess expensive than IGRAMore subjective determination of resultsUnreliable results for children under age 6 monthsQA issues with both tests:TST in administration, subjectivity in reading and interpretationIGRA in blood draw technique and timing to labLess subjective results with IGRA; qualitative and quantitative results vs. TST reading
29 Commonalities between TST and IGRA BOTH dependent on a functioning immune systemIf negative, neither rule out TB diseaseGenerally, not recommended to be used sequentially, i.e. one to confirm the otherSequential use of TST and IGRA in either order actually reduces the tests sensitivity