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Tuberculosis Screening and Testing of College and University Students

Frequently Asked Questions

 
After releasing the revised ACHA Guidelines: Tuberculosis Screening and Targeted Testing of College and University Students, the TB Task Force received numerous questions with common themes. Members of the American College Health Association (ACHA) Emerging Public Health Threats & Emergency Response Coalition decided to use these themes to guide a Frequently Asked Questions (FAQ) document.

References are included where they exist. Readers are encouraged to refer to cited works for elaboration of the answers below. When research does not exist or is inconclusive, our answers are consensus- and practice-based. Not all answers will apply to all colleges and universities. Each institution should make decisions about their TB programs based on their individual circumstances and in consultation with additional resources such as state and local TB program officials to determine the most appropriate course of action for their specific patient populations.


March 2012

Questions

Q1: The financial costs to implement a TB screening and testing policy that meets ACHA's TB guidelines can be significant. We have not had a case of TB on our campus for several years. What are the arguments to support the need for a TB policy on our campus?

Q2: How often will the "high incidence countries list" in ACHA's TB guidelines be updated?

Q3: Why does ACHA use incidence rates instead of prevalence rates?

Q4: Why did ACHA select the incidence rate of 20 cases/100,000 population/year?

Q5: We don't have the resources to identify and/or screen students from all these countries. Can we use other criteria?

Q6: What should we require of students returning from study abroad or travel to high incidence countries?

Q7: What should be done with a student who reports prior treatment for LTBI but has no documentation?

Q8: What strategies are most effective in getting students with LTBI to accept treatment?

Q9: Should anything be done with students who have LTBI but decline treatment?

Q10: How can health centers with only a single nurse or a very small staff start/implement a TB screening/testing program?

Q11: In what circumstance should I choose a TST and in what circumstance should I use an IGRA in my choice of initial test for TB infection?

Q12: TSTs are less costly; can we use a TST and then do an IGRA for positive TST?

Q13: If TST is positive, but IGRA is negative, is a chest x-ray needed?

Q14: Can T-spot be used interchangeably with QFT-G/QFT-GIT? Or how is T-SPOT.TB different from QFT?

Q15: If a chest x-ray is needed, how many views are needed?

Q16: Are IGRAs sometimes negative in patients with active tuberculosis? How common are false negative IGRAs?

Q17: Can prior TSTs cause a false positive IGRA result?

Q18: How can we get a lab near us to do IGRAs?

Q19: What is meant by a "significant" exposure in terms of length of time in a high incidence country, length of time working at a homeless shelter, mission trip, etc.?

Q20: Should written documentation of prior positive TST or IGRA be required and if so, should foreign documents be accepted?

Q21: Should a report of a negative chest x-ray be accepted when the student has a positive TST or IGRA?

Q22: A student reports a history of positive TST but has no documentation. What are the options?

Q23: Are chest x-rays repeated annually?

Q24: What should be considered when testing incoming health care professional students for TB infection?

Q25: How often should TB testing be repeated for health care professional students?

Q26: What is the proper procedure for health care professional students who have had a prior positive test for TB?


 
March 2012

Answers

Q1: The financial costs to implement a TB screening and testing policy that meets ACHA's TB guidelines can be significant. We have not had a case of TB on our campus for several years. What are the arguments to support the need for a TB policy on our campus?

A1. The primary purposes of a TB screening program are to maintain a healthy and safe campus environment and to reduce the direct and indirect costs associated with a case of tuberculosis disease on campus.

Many campuses follow policies designed to insure safety of students including the prevention of infectious diseases.

The airborne spread and risk of contagion make tuberculosis a particularly dangerous infection. Adverse publicity, liability, and allegations of negligence could present significant problems for an institution without a policy, especially since existing screening and treatment recommendations are widely implemented elsewhere.

A campus with international students from countries with high incidence of TB presents opportunities to identify and treat latent tuberculosis infection (LTBI). This is an effective way to decrease the number of active TB cases among foreign-born individuals in the U.S.

Expenses associated with TB disease include the direct cost of diagnosis and treatment of the active case and many unmeasured societal costs. Other costs include infrastructure, diagnosis and surveillance, epidemiologic follow up, personal costs borne by patients and others for lost time, disability and death as well as cost of secondary transmission. The costs to manage a single case of disease may easily exceed the costs to screen high-risk populations. Preventing disease through early diagnosis and treatment of LTBI is a feasible strategy to reduce the cost of TB.

References: 1, 2, 3, 4, 5, 6, 7, 8

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Q2: How often will the "high incidence countries list" in ACHA's TB guidelines be updated?

A2. The ACHA list of countries that have a high burden of TB is derived from data provided by the World Health Organization (WHO). It is updated regularly when new incidence rates are published by WHO, usually every one to two years. You may access the WHO Global Health Database at http://apps.who.int/ghodata if you wish to view current data and other country-specific information.

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Q3: Why does ACHA use incidence rates instead of prevalence rates?

A3. Incidence rates reflect recent new cases of disease and are a more accurate representation of active TB infections occurring in the country. Prevalence rates reflect the general burden of disease in the population. Both are valid measures and can be used to guide screening programs. Most countries with incidence rates greater than 20 cases/100,000 population also have prevalence rates above this level. In addition, the U.S. Centers for Disease Control and Prevention (CDC) uses incidence rates in most guidance regarding persons at higher risk for exposure to tuberculosis.

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Q4: Why did ACHA select the incidence rate of 20 cases/100,000 population/year?

A4. This is an arbitrary cut-off commonly seen in the relevant literature. While some authorities would favor screening people from any country with an incidence rate higher than the U.S. (about 4 cases/100,000), the ACHA TB Task Force felt that limiting screening to students arriving from countries designated as being at either moderate or high risk was reasonable. In general, countries with incidence rates of 20-100 cases/100,000 are usually considered to be "moderate" risk, and countries below this level are considered to be at "low" risk.

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Q5: We don't have the resources to identify and/or screen students from all these countries. Can we use other criteria?

A5. The majority of U.S. cases among foreign-born individuals are in people from seven countries (China, Guatemala, Haiti, India, Mexico, Philippines, and Vietnam). About 80% of TB cases world-wide occur in just 22 “high-burden” countries. Local epidemiologic profiles are often the most useful resource to identify countries of highest risk, but local immigration patterns may be very different than international student enrollment.

References: 9, 10

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Q6: What should we require of students returning from study abroad or travel to high incidence countries?

A6. Students who travel to areas of the world where tuberculosis is endemic should be considered for screening when they return. The risk of infection depends on the duration of travel, the level of contact with the local population, and other factors. As noted in ACHA's TB guidelines, little data exists regarding the specific exposures associated with acquisition of infection during travel. Colleges and universities are advised to consult with their local public health departments and/or a travel health provider for guidance.

Some experts recommend both pre-departure and post-travel testing for travelers who will be in endemic areas for greater than one month, especially if they will have close contact with the local population or work in high-risk settings (health care, refugee camps). This would apply to students in many study-abroad programs. Students should discuss their specific travel circumstances with a health care provider who can determine the appropriate evaluation.”

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Q7: What should be done with a student who reports prior treatment for LTBI but has no documentation?

A7. It is often difficult to assess whether a student who gives a verbal report of treatment for TB (latent or active) was adequately treated with the appropriate medications for the right amount of time. This is important information to ascertain, when possible, because inadequately treated TB can give rise to drug-resistant TB. However, we sometimes see situations where students just cannot get documentation of their treatment.

Gather as many details about their treatment as possible, and document this information in the student's health record. Include the country where treated, results of a chest x-ray, duration of treatment, frequency of dosing, dates of treatment, and name of medication. It may become clear that the student was treated appropriately and further treatment is not warranted. In other cases, little to no information will be available. Additional treatment or follow- up may be recommended, depending on the patient's risk for progression. Consultation with local public health staff and/or infectious disease specialists is recommended.

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Q8: What strategies are most effective in getting students with LTBI to accept treatment?

A8. Success in motivating patients to accept and to complete treatment is critical to achieve the full potential of a screening program. Some students will be motivated to protect their own health — the risk of progression to active disease — while others will respond to concerns about transmission to loved ones. Reducing barriers to treatment by providing flexible clinic hours, reducing waiting times for patients, and spending time with patients to counsel and educate them, can all make a difference.

The addition of an IGRA test may be useful when an initial TST is positive and additional evidence of infection is required to encourage compliance. This approach may be helpful for students with a history of BCG vaccination who are skeptical of an LTBI diagnosis based on TST alone.

References: 10, 13

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Q9: Should anything be done with students who have LTBI but decline treatment?

A9. Respect the student's decision without being judgmental, and always leave open the option for future treatment should they change their mind. The health care provider should fully explain the risks and benefits of treatment to the student, including the risk of progression to active disease, and document the conversation in the student's health record. Keep in mind that LTBI is not infectious and treatment is not mandatory from a public health perspective. Regardless of whether the patient opts for treatment for LTBI, serial or repeat chest radiographs are not indicated unless the patient develops signs or symptoms suggestive of TB disease.

References: 10, 14

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Q10: How can health centers with only a single nurse or a very small staff start/implement a TB screening/testing program?

A10. Smaller schools often have a very small health center, with few nursing staff. Some of these centers are directed by nurses, with no physician or clinician on site. These clinics are likely to have a limited budget, and may have no laboratory locally to provide IGRA tests.

All schools implementing or managing a TB screening/testing program should be familiar with the CDC Core Curriculum on Tuberculosis: What the Clinician Should Know and Latent Tuberculosis Infection: A Guide for Primary Health Care Providers.

A policy and procedure should be developed identifying the target population to be tested, the time-frame for testing, the process, costs, follow-up procedures and requirements for students who do not follow the procedure.

In developing a program, the nurse should contact the local public health official in charge of TB control for advice and referral. If no public health services are available locally, a family physician may be willing to provide follow-up. Medical follow-up will be necessary for positive results of either test, and will likely include a TB symptom check, chest x-ray, and patient education.

References: 10, 12

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Q11: In what circumstance should I choose a TST and in what circumstance should I use an IGRA in my choice of initial test for TB infection?

A11. Both the TST and the IGRA tests are good and acceptable tests for TB infection. The CDC has made recommendations as to which are preferred based on risk factors of the individual being tested. Please see the chart below.

Risk Group

U.S. Guideline

Close contacts of persons with infectious TB

TST or IGRA, but not both

Persons who may not return for TST reading because of circumstances (e.g., homelessness or injection drug-use) or logistic difficulties

IGRA preferred

Immunosuppressed persons (e.g. those infected with HIV or receiving treatment with prednisone or TNF inhibitor)

TST or IGRA; use both if first is negative and suspicion is high

Foreign-born persons

Screening only for those who have immigrated in past 5 years; use TST or IGRA, but not both

BCG vaccine recipients (if they belong to another risk group)

IGRA preferred

Health care workers (screening program)

TST or IGRA but not both

Children < 5 yr old

TST preferred

Other risk groups

TST or IGRA but not both

 
Key points:

  1. The TST and IGRA can be used on any individual.
  2. The IGRA test is preferred in individuals with history of BCG vaccination.
  3. Routine testing with both a TST and an IGRA is not recommended.

References: 12, 14

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Q12: TSTs are less costly; can we use a TST and then do an IGRA for positive TST?

A12. Each institution may have different practices based on local data and experts but at this time, the CDC does not recommend performing both a TST and an IGRA on an individual.

Generally the cost of one TST is less than the cost of an IGRA. This cost benefit may be lost when more than one TST is recommended, for e.g., health science students or health care professionals who are required to have an initial screening with a two-step TST.

In some cases in which a TST is positive, it is the provider's discretion whether an IGRA should be done. Some believe that individuals with a positive TST and a subsequent positive IGRA might be more inclined to initiate treatment for latent TB once active TB is excluded.

Reference: 15

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Q13: If TST is positive, but IGRA is negative, is a chest x-ray needed?

A13. Any positive TB screening test should be followed by a check for TB signs and symptoms and a chest x-ray to rule out active TB. If any signs and symptoms of active TB disease exist, further testing (typically including a sputum evaluation) should be done. Both the TST and the IGRA can be negative in both active and latent TB. Test results are never a substitute for sound clinical judgment.

A positive TST can represent four scenarios: TB infection, a false positive test, a result of the BCG vaccination or an atypical mycobacterial infection. Some experts believe the IGRA may be a more sensitive test for recent TB exposure while a TST is a more sensitive test for remote exposures.

If the individual has a positive TST of less than 15mm, does NOT have any risk factors for progression to active TB if infected, has had BCG vaccination, and the decision is made to do an IGRA which turns out to be negative, it is reasonable to not do a chest x-ray. This could represent a false positive test or an atypical mycobacterial infection. Another possibility is to repeat the IGRA at a future time (e.g., 3-12 months) to make sure the patient has not had a recent TB exposure. This should be decided on a case by case basis.

References: 12, 15, 16

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Q14: Can T-spot be used interchangeably with QFT-G/QFT-GIT? Or how is T-SPOT.TB different from QFT?

A14. Either the T-SPOT.TB or the Quantiferon tests can be used to test individuals for TB infection. Most experts suggest that there is no convincing data that one test is consistently better than another and test choice should be based on availability, price, and convenience.

The use of IGRAs for serial testing has not been extensively studied and should not generally be used until more data is available. Also, there is a "wobble" phenomenon in which a positive result close to the cut-off point on one occasion may have a different result if retested by the same test. Thus, in cases in which subsequent or serial IGRA testing is done, the T-SPOT.TB should not be used interchangeably with the Quantiferon tests (i.e. the same test should be used on the same individual over time). Significant between-study variability in the test characteristics of both the Quantiferon and T-SPOT.TB tests are noted in numerous studies.

References: 12, 14, 15, 16

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Q15: If a chest x-ray is needed, how many views are needed?

A15. Unless the patient is a child less than five years old, the posterior-anterior (PA) view is the standard view used for the detection of TB-related chest abnormalities. Other views or additional studies may be requested by the health care provider or the radiologist interpreting the x-ray to clarify any inconsistencies.

Reference: 17

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Q16: Are IGRAs sometimes negative in patients with active tuberculosis? How common are false negative IGRAs?

A16. Yes, IGRAs can be negative in patients with active tuberculosis. Reasons for false negative results include: incorrect blood sample collection, improper specimen handling, recent tuberculosis exposure, or immunosuppressive conditions.

There is no gold standard test for latent tuberculosis infection or culture-negative active tuberculosis. Furthermore, any assessment of negative and/or positive predictive value is dependent on prevalence of the disease in the population of interest.

Estimates of IGRA sensitivity have varied widely and are dependent on interpretive criteria used to define test positivity. In general, the pooled QFT-GIT sensitivity is reported to be around 80-84% while the T-SPOT.TB sensitivity is estimated to be around 88-95%. The sensitivity of both tests is higher in developed, low-incidence countries such as the U.S.

References: 12, 18, 19

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Q17: Can prior TSTs cause a false positive IGRA result?

A17. There is conflicting literature regarding the influence of prior tuberculin skin testing on the results of subsequent IGRA results. A recent systematic review of this topic concluded that while the data regarding this question was scarce, evidence suggested that in IGRA-negative individuals, the interpretation of results may be confounded by a preceding TST if administered more than three days prior to an IGRA. However, since this article's publication, two additional studies were unable to demonstrate a boosting phenomenon induced by previous TST.

References: 20, 21, 22

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Q18: How can we get a lab near us to do IGRAs?

A18. IGRA tests are relatively straightforward to perform and are cost-effective. Whether your lab is able to support the addition of a new test will likely be determined by the level of demand and local resources.

The QFT-GIT test is also available through national reference laboratories. Cellestis, the manufacturer of the QFT-GIT also has an online QFT locator tool (www.cellestis.com/IRM/Content/usa/contact_quantiferon.html).

Oxford Diagnostic Laboratories in Marlborough, Massachusetts, is the national reference laboratory for T-SPOT.TB testing. Blood can be collected in a standard lithium or sodium heparin collection tube and sent Monday through Saturday, with test results available within 36-48 hours.

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Q19: What is meant by a "significant" exposure in terms of length of time in a high incidence country, length of time working at a homeless shelter, mission trip, etc.?

A19. No definition or guideline exists as to what is a "significant" TB exposure. The degree of communicability of TB from one person to another depends on many factors:

  • intimacy of exposure
  • duration of exposure
  • quantity of bacilli discharged
  • infectivity of the bacilli
  • ventilation
  • exposure of the bacilli to sun or ultraviolet light
  • opportunities for aerosolization through coughing, sneezing, talking, or singing
  • immune status of the person being exposed

CDC defines a contact as "a person who has spent time with a person with infectious TB." CDC recommends that persons should get tested for TB if they have spent time with a person known or suspected to have active TB disease, if they have HIV infection, or if they have another condition that weakens their immune system and puts them at higher risk for active TB disease.

CDC indicates that persons who had prolonged, frequent, or intense contact with a person with TB while he or she was infectious are considered to be exposed. Close contacts are more likely to become infected with M. tuberculosis than contacts who see the person with TB less often. CDC indicates that exposure related to households, congregate living settings, or cough-inducing medical procedures, are designated as higher risk. Because knowledge is insufficient for providing exact recommendations, cut-off points for duration of exposure are not included. State and local program officials should determine cut-off points after considering published results, local experience, and these guidelines. Colleges and universities are encouraged to consult with local public health departments and other TB experts to determine how best to apply this information to their specific patient populations.

References: 10, 23, 24, 25, 26, 27

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Q20: Should written documentation of prior positive TST or IGRA be required and if so, should foreign documents be accepted?

A20. Any institution that tests for TB infection, including academic institutions, should require written documentation of previous test results. Foreign documents that are translated into English may be accepted. A TST that was not measured and recorded in mm of induration should be repeated.

References: 28, 29

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Q21: Should a report of a negative chest x-ray be accepted when the student has a positive TST or IGRA?

A21. Yes. A normal chest x-ray, when considered as a part of the entire clinical picture which includes a test for TB infection and TB symptom evaluation, indicates an absence of active TB. A positive TST or IGRA test, on the other hand, only indicates whether the person has been exposed to TB organisms.

A student with a prior positive test for TB infection (TST or IGRA), a negative TB symptom check, and written documentation of a negative chest x-ray can be cleared. The chest x-ray does not need to be repeated.

Reference: 30

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Q22: A student reports a history of positive TST but has no documentation. What are the options?

A22. A TST could be administered, unless the person reports previous severe reaction to purified protein derivative (PPD). A good alternative in this situation would be to do an IGRA. Subsequent IGRAs can be performed on people with previously positive IGRA results.

References: 12, 29, 30

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Q23: Are chest x-rays repeated annually?

A23. No. To exclude a diagnosis of active TB, persons with a positive test for TB infection (TTBI) should receive a TB symptom check, a single baseline chest x-ray and medical evaluation to exclude active TB. Repeated chest x-rays are not recommended unless symptoms or signs of active TB disease develop or unless recommended by a health care provider.

Reference: 31

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Q24: What should be considered when testing incoming health care professional students for TB infection?

A24. For infection prevention and control purposes, health care professional students are subject to the same guidelines as health care workers. If they will share air space with patients, health care professional students should be tested for TB infection upon matriculation, unless they have documentation of a prior positive test for TB infection. Baseline testing for new health care professional students should be done with either a two-step PPD skin test or a single IGRA blood test for TB infection.

Reference: 31

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Q25: How often should TB testing be repeated for health care professional students?

A25. After initial testing as described above, all health care professional students with a negative test for TB infection should be tested for TB annually. Students who have documentation of a positive test and/or treatment for latent or active TB should have a TB symptom check annually.

Reference: 31

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Q26: What is the proper procedure for health care professional students who have had a prior positive test for TB?

A26. Health care professional students with documentation of a positive test for TB infection and subsequent negative chest x-ray and negative TB symptom check, or with documentation of a completed course of treatment for latent TB infection or active TB, should have a TB symptom check upon matriculation and annually.

References: 31, 32

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