Tuberculosis (TB) is a serious infectious disease, and the tuberculin skin test (TST), also known as the Mantoux test, is a common method for detecting infection with Mycobacterium tuberculosis. While a positive TST doesn't necessarily mean active TB disease, it indicates exposure to the bacteria and requires further investigation. This article will explore what a positive TST looks like, the interpretation of results, and the next steps involved.
What is a Positive Tuberculin Skin Test?
A positive TST result is indicated by a raised, hardened area (induration) at the injection site. The size of this induration determines the positivity, and the interpretation varies depending on the individual's risk factors (e.g., recent contact with a TB patient, immunosuppression, HIV infection). A healthcare professional will carefully measure the induration in millimeters.
Interpreting the Induration
The size of the induration is crucial:
- > 15 mm: Generally considered positive in most individuals.
- 10-15 mm: Positive in individuals with risk factors like recent immigration from high-prevalence countries, intravenous drug users, residents of high-risk congregate settings (prisons, nursing homes), or those with compromised immune systems.
- 5-9 mm: Positive only in individuals with severely compromised immune systems (e.g., HIV infection, organ transplant recipients, or those taking immunosuppressants).
Important Note: Only a healthcare professional can interpret the results accurately. The presence of redness (erythema) alone is not indicative of a positive test. It's the hardened area (induration) that matters.
Images of Positive Tuberculin Skin Tests
Unfortunately, I cannot display images directly within this text. However, searching online for "positive Mantoux test images" or "positive tuberculin skin test pictures" will yield numerous visual examples. These images typically show a raised, firm area of induration at the injection site, often with less surrounding redness. The size of the induration will vary depending on the individual's reaction.
Remember, visual interpretation should only be used as a general guide. A healthcare provider should always be consulted for a definitive diagnosis.
What to Do if Your Tuberculin Skin Test is Positive
A positive TST doesn't automatically mean you have active TB disease. It indicates that you've been exposed to the bacteria and have developed an immune response. Further testing is necessary to determine if you have latent TB infection (LTBI) or active TB disease. These tests may include:
- Chest X-Ray: To rule out active TB lung disease.
- Sputum Culture: A test to identify the bacteria in your sputum (cough).
- Interferon-Gamma Release Assays (IGRAs): Blood tests that can detect the presence of TB antibodies.
Preventing the Spread of TB
If you have a positive TST, it's crucial to follow your healthcare provider's recommendations for treatment. This might involve preventative therapy for LTBI to prevent the infection from progressing to active TB. Early diagnosis and treatment are essential for preventing the spread of tuberculosis.
Conclusion
The tuberculin skin test is a valuable tool in detecting exposure to Mycobacterium tuberculosis. However, a positive result requires further investigation to determine if active TB disease is present. Healthcare professionals should interpret the TST results, and appropriate follow-up testing is crucial for diagnosis and treatment. Remember to consult a healthcare provider if you have concerns about your TST result or symptoms suggestive of TB. Remember to always seek medical advice for any health concerns.
