1. VDH TB Control and Prevention Program
The TB Risk Assessment
VDH TB Control and Prevention Program
2011

2. Why do a TB risk assessment?
Identify those in need of further testing for TB disease
Meet job or program requirements
Identify 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 infected
Those with clinical conditions that increase their risk of progressing from LTBI to TB disease
This 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 TB
Skin 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 TST
Residents 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 TB
Underweight or malnourished persons
Injection drug users
Those receiving TNF-α antagonists for treatment of rheumatoid arthritis or Crohn’s disease
Persons with certain medical conditions such as
HIV, DM, CRF/dialysis, silicosis, organ transplant,
CA of head/neck, gastrectomy or jejunoilial bypass
This 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 populations
TB 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:
Symptoms
Risk for acquiring TB infection
Risk for progressing to TB disease if infected
It 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 employees
Foster care parents
Day care employees
School employees
Residential school attendees
*TST or IGRA is indicated if there is a risk factor on the risk screen
A chest x-ray is indicated for positive TST or IGRA
A full diagnostic work-up is needed if symptoms consistent with TB

8. Who can sign the “free from TB” statement?
Physician
Public Health Nurse or Clinician
Physician’s Assistant or Nurse Practitioner if for Adult Day Care
For 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 workers
Students preparing for health care careers
Adult day care participants
Anyone who will be serially tested with TST or IGRA
All 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 infection
Is 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 disease
The other way is the IGRA blood test that we will talk about in the next section.

11. The Tuberculin Skin Test or TST

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 intradermally
Evaluated (read) 48 to 72 hours after administration
Cross reacts with other mycobacteria, including BCG vaccine
A history of BCG vaccine is not a contraindication

13. TST Result: False Positive
Possible causes
Non-tuberculous mycobacteria
BCG vaccination
Routinely administered to children in countries where TB is prevalent
Not a contraindication for the administration of the TB skin test
Wanes over time ; if TST is + likely
due to TB infection if risk factors present

14. TST Result: False-Negative
Causes include
Anergy / immune suppression
Recent TB infection (within past 10 weeks)
Very young age (younger than 6 months old)
Incorrect administration and storage of test solution
Live-virus vaccination within 4-6 weeks
Overwhelming TB Disease
Poor TST administration technique
Anergy 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 + PERSONS
Recent 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 disease
Very 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 TST
Inject 0.1 ml of 5 tuberculin units of liquid tuberculin, intradermally, using a 27 gauge needle with bevel up
Use the volar surface of forearm when possible
May use the scapular area if forearm
Produce a wheal 6 to 10 mm in diameter
Advise no creams, band-aids, scratching
May shower or swim
Record the site, lot number, date and time of administration, and person giving the test
We 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 tuberculin
Most people with TB infection have a positive reaction to the tuberculin
The 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 injected
Assess the injection site for erythema (redness) and induration (swelling that can be felt) by lightly palpating the area
Measure 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 recommended
If 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 disease
Cut points for positivity are at 5, 10, and 15 mm
It 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 infection
Close contacts of people with infectious TB
Persons with fibrotic chest x-ray findings suggestive of prior TB disease
Patients with organ transplants
Persons 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 users
Residents and employees of high-risk congregate settings
Mycobacteriology laboratory personnel
People with clinical conditions that place them at high risk (those listed on risk screen)
Children < 4 years old
Infants, children and adolescents exposed to adults in high-risk groups
Persons 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 TST
Educate patient and family regarding significance of a positive TST result
Positive TST reactions can be measured up to 7 days after administration
Negative reactions must be read between hours after administration
Significance = 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 Phenomena
ability to react to tuberculin may wane with time
a TST may prompt new antibody production
a second TST detects this “boosted,” increased response
Two-step testing – two TSTs, 1 to 3 weeks apart
Use with groups who will have repeated TSTs as part of infection control programs
Avoids a “boosted” test classified as new positive, which could reflect undetected transmission
Two 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 neg
If 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 test
or 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 tuberculosis
If person has been infected with M. tuberculosis, lymphocytes will respond by producing IFN-γ
The 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 testing
Preferred for those with Hx of BCG vaccination – no cross reactivity with BCG vaccine
Do cross react with a few NTMs
May be preferred for those who are not likely to return for TST reading (SA, homeless, etc.)
Two types of tests approved by the FDA
QuantiFERON TB Gold-in-Tube or QFT-GIT
T-Spot TB
Results are both quantitative and qualitative
Cross 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.

26. QuantiFERON TB Gold-in-Tube Sample Results
Explain why

27. T Spot Sample Result Positive - Nil ≤ 10 spots TB Antigen ≥ 8 spots
Mitogen - Any Response
Negative - Nil ≤ 10 spots
TB Antigen ≤ 4 spots
Borderline 5,6, or 7 spots
Table 3 Interpretation Criteria for T.Spot TB, CDC Guidelines, pg. 16

28. Comparison of IGRA vs. TST
One visit
No cross reaction with BCG
Limited time frame from draw to incubation in lab
More expensive than TST
Less subjective determination of results
Not approved for children under age 5 years
Two visits (4 for two-step test)
Cross reacts with BCG with potential for false positives
Time frame constraint for reading
Less expensive than IGRA
More subjective determination of results
Unreliable results for children under age 6 months
QA issues with both tests:
TST in administration, subjectivity in reading and interpretation
IGRA in blood draw technique and timing to lab
Less subjective results with IGRA; qualitative and quantitative results vs. TST reading

29. Commonalities between TST and IGRA
BOTH dependent on a functioning immune system
If negative, neither rule out TB disease
Generally, not recommended to be used sequentially, i.e. one to confirm the other
Sequential use of TST and IGRA in either order actually reduces the tests sensitivity

30. ?? Questions ??