The Mantoux test, also known as the tuberculin skin test (TST), is a widely used method for diagnosing Tuberculosis (TB), a potentially serious infectious disease primarily affecting the lungs. Despite the decline in TB incidence in many countries, it remains a significant public health concern, making early detection essential. This blog will explore what the Mantoux test is, its uses, the procedure for administration, and how to interpret the results.

What is the Mantoux Test?

The Mantoux test is a diagnostic skin test that measures the immune response to a Purified Protein Derivative (PPD) of the Mycobacterium Tuberculosis bacteria. When this protein is injected intradermally (just under the skin), it stimulates the immune system in individuals who have been exposed to TB. The test is primarily used to determine if someone has been infected with the TB bacteria, regardless of whether they have developed active TB disease.

Why is the Mantoux Test Used?

The Mantoux test is crucial for several reasons:

  1. Early Detection of TB: Identifying individuals with latent TB infection (LTBI) is essential to prevent the progression to active TB disease. The test can help healthcare providers determine who may need further evaluation or treatment.
  2. Screening High-Risk Populations: The test is particularly important for individuals at higher risk of TB exposure, including healthcare workers those with compromised immune systems and individuals living in close quarters such as shelters or correctional facilities.
  3. Pre-Employment and Immigration Requirements: Many employers and countries require a Mantoux test as part of their health screenings to ensure that individuals do not pose a risk of TB transmission.

Procedure: How is the Mantoux Test Administered?

The Mantoux test involves a straightforward procedure that can be performed in a healthcare setting:

  1. Preparation: The healthcare provider will start by reviewing the patient’s medical history and discussing any potential allergies to components of the test.
  2. Injection: A small amount (usually 0.1 mL) of tuberculin PPD is injected intradermally into the inner forearm. The injection creates a small raised bump on the skin which is a normal reaction.
  3. Aftercare: Patients is advised not to scratch or cover the injection site and must be instructed to return for a reading of the test within 48 to 72 hours.

Interpreting the Results

The results of the Mantoux test are read by a healthcare professional within the specified timeframe. The interpretation depends on the size of the induration (swelling) at the injection site:

  • Positive Result: An induration of 15 mm or more is considered positive in individuals with no known risk factors for TB. A positive result indicates that the person has been infected with the TB bacteria at some point, but it does not distinguish between latent TB infection and active TB disease.
  • Negative Result: An induration of less than 5 mm is generally considered negative. However, results can vary based on the individual’s risk factors. For example, a positive result of 10 mm or more is often required for those in higher-risk groups, such as healthcare workers or individuals with weakened immune systems.
  • Follow-Up: If the test is positive, further evaluation, such as a chest X-ray or sputum tests may be necessary to determine if active TB disease is present.

Conclusion

The Mantoux test remains a valuable tool in the fight against Tuberculosis. By identifying individuals with latent TB infection, healthcare providers can intervene early reducing the risk of disease transmission and improving public health outcomes. Understanding the test’s purpose, procedure and interpretation is essential for individuals and healthcare professionals alike, contributing to the broader goal of controlling and eventually eradicating tuberculosis.