Tuberculin Skin Test
Also written as TST.
| Tuberculin skin test / Interferon‑γ release assay | Is latent or active TB present in silica‑exposed workers? | Positive test + compatible CXR → silico‑TB; warrants chemoprophylaxis |
What our notes say
- | Tuberculin skin test / Interferon‑γ release assay | Is latent or active TB present in silica‑exposed workers? | Positive test + compatible CXR → silico‑TB; warrants chemoprophylaxis | (Occupational Lung Disease)
- In a study\n(or postprimary) tuberculosis, which, because of frequent of HIV-infected, tuberculin skin test (TST)–positive\ncavitation, is more often infectious than is primary dis- persons, this risk varied from 2.6 to 13.3 cases per 100\nease. (Harrisons Pulmonary and Critical Care Medicine)
- Tuberculin skin tests are, of all tests, the most useful in the (Devendra K. Gupta, Krishna M. Goel - Hutchison’s Paediatrics. chdhe-Jaypee Broth)
- Tuberculin skin test-Useful test to detect TB exposure in children and support presumptive clinical diagnosis in situations where there is no obvious close TB contact to the child\nInterferon gamma reaction assay (IGRA)-Similar role to TST but more expensive. (PULMONARY TUBERCULOSIS)
- Tuberculin skin test or interferon-gamma release assay (shows exposure, not active disease). (Junior Clerkship in Internal Medicine (MBIM4100) main exam, Paper One: 31 Januar)
- culosis-endemic areas receive BCG.\na\nTuberculin-negative contacts, especially children, should receive\nprophylaxis for 2 to 3 months after contact ends and should then\nundergo a repeat tuberculin skin test (TST). (Harrisons Pulmonary and Critical Care Medicine)
Study material on Tuberculin Skin Test
- Harrisons Pulmonary and Critical Care Medicine
- 4 Fundamentals of TB
- Fundamentals of TB
- TB
- PULMONARY TUBERCULOSIS
- Devendra K. Gupta, Krishna M. Goel - Hutchison’s Paediatrics. chdhe-Jaypee Brothers (2012)
- MBMM 3311 Medical Bacteriology Examination — Notes
Practice questions on Tuberculin Skin Test
A positive tuberculin skin test, with a firm 15 mm diameter dark red area of induration on the forearm, appears 60 hours after injection of purified protein derivative (PPD). This finding is most likely a consequence of which type of hypersensitivity reaction?
- Type I hypersensitivity
- Type II hypersensitivity
- Type IV hypersensitivity
- Type III hypersensitivity
- Complement activation
Answer: C. * The tuberculin skin test relies on an intact cell-mediated immune response. It is positive with prior mycobacterial exposure, so memory T cells are present and can be reactivated.
A positive tuberculin skin test shows 15 mm of firm dark red induration at 60 hours after PPD injection. Most likely type of hypersensitivity reaction?
- Complement activation
- Type I hypersensitivity
- Type IV hypersensitivity
- Type II hypersensitivity
Answer: C. Delayed reaction peaking at 48–72 hours + induration (not just redness) + requires prior sensitization = type IV (cell-mediated/delayed-type) hypersensitivity, mediated by memory T lymphocytes responding to mycobacterial antigens.
The Mantoux test (tuberculin skin test) is used to detect exposure to Mycobacterium tuberculosis.
- B) Current TB infection
- A) TB exposure
- C) Past TB infection only
- D) BCG vaccination status
Answer: B. The Mantoux test indicates that a person has been infected with M. tuberculosis at some point. It does not distinguish between active infection, latent infection, or prior BCG vaccination, and requires further evaluation for diagnosis of active TB.
The Mantoux test (tuberculin skin test) is used to identify:
- Active tuberculosis infection
- Past exposure to Mycobacterium tuberculosis
- BCG vaccination status
- The specific strain of tuberculosis
Answer: B. The Mantoux test is a delayed-type hypersensitivity reaction that indicates prior exposure to Mycobacterium tuberculosis. It does not distinguish between active infection and latent infection or past exposure.