Hello everyone,
This week in lecture we discussed Mycobacterium tuberculosis. Just so happen this very same week I had to renew my annual TB skin test. This made me wonder, what was the big deal that we had to get tested for TB each year. So I did some research and I found that transmission of tuberculosis, including multidrug-resistant tuberculosis, is a recognized risk for laboratory workers. Health care workers in general are considered to be apart of the high-risk infection groups for Tuberculosis. UAB state that, "Given the nature of their work, students engaged in health professional training programs could have a higher risk of contracting Rubeola, Rubella, Mumps, Tetanus, Diphtheria, Varicella, Tuberculosis, Pertussis, and Hepatitis B. All UAB students in the Joint Health Sciences programs and in the Schools of Medicine, Dentistry, Optometry, Public Health, Nursing, and Health Professions are required to be immunized."
So what does UAB require for Tuberculosis Screening?
- All international students and scholars must show proof of a non-reactive Tuberculin skin test or negative blood test (Quantiferon), or appropriate treatment if positive, within three months prior to enrollment or visiting
- PPD (skin test) screening requires a 2-step process, with PPD (skin test) placements at 1-3 weeks apart.
- Non-reactive (negative) Tuberculin skin test or chest x-ray reports done outside the United States will not be accepted.
- Individuals with a history of a reactive Tuberculin skin test or blood test must provide a current chest x-ray (taken since their last positive TB test but within three months prior to enrollment or visiting), indicating that the person is free of active tuberculosis. Individuals with a positive TB screening test should complete the TB Questionnaire, submit it to Student Health Services, and consult the UAB Student Health Services TB Testing Policy to view the required follow-up.
So what is the TB skin test:
The Mantoux tuberculin skin test (TST) is the standard method of determining whether a person is infected with Mycobacterium tuberculosis. The TST is performed by injecting 0.1 ml of tuberculin purified protein derivative (PPD) into the inner surface of the forearm. The TST is an intradermal injection and when placed correctly, the injection should produce a pale elevation of the skin 6 to 10 mm in diameter. The skin test reaction should be read between 48 and 72 hours after administration. The reaction should be measured in millimeters of the induration (palpable, raised, hardened area or swelling), making sure not to measure the erythema (redness). The diameter of the indurated area should be measured across the forearm.
How Are TST Reactions Interpreted?
Classification of the Tuberculin Skin Test Reaction:
An induration of 5 or more millimeters is considered positive in
-HIV-infected persons
-A recent contact of a person with TB disease
-Persons with fibrotic changes on chest radiograph consistent with prior TB
-Patients with organ transplants
-Persons who are immunosuppressed for other reasons (e.g., taking the equivalent of >15 mg/day of prednisone for 1 month or longer, taking TNF-a antagonists)
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An induration of 10 or more millimeters is considered positive in
-Recent immigrants (< 5 years) from high-prevalence countries
-Injection drug users
-Residents and employees of high-risk congregate settings
-Mycobacteriology laboratory personnel
-Persons with clinical conditions that place them at high risk
-Children < 4 years of age
- Infants, children, and adolescents exposed to adults in high-risk categories
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An induration of 15 or more millimeters is considered positive in any person, including persons with no known risk factors for TB. However, targeted skin testing programs should only be conducted among high-risk groups.
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So as you can see from the chart, laboratory personnel and other adults in high-risk categories induration measurement is greater other categories to be consider positive.
So as students, we should understand our risk and take the TB screening process seriously. I know we are all busy, but we shouldn’t put it off. Make sure to get your TB screening annually and take the necessary precaution to remain TB negative.
Also, I have included a few links: two on Mycobacterium tuberculosis to provide more information on the bacteria and disease and one on the TB skin test Mantoux Method that I mention above. Also I have included a link from a journal insert on Tuberculosis in laboratory workers. If you are interested please check them out.
As always, read, comment, and post!
Thanks for reading!!!
Tuberculosis Http://www.youtube.com/watch?V=jtyx694ubio
Mycobacterium tuberculosis Http://www.youtube.com/watch?V=u7o93nmgp1e
Tuberculosis in laboratory workers http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1961675/pdf/brmedj03110-0055.pdf
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