The Mantoux test, also known as the Tuberculin Skin Test (TST) or Purified Protein Derivative (PPD) test, is a standard method used to screen for exposure to the bacteria that causes Tuberculosis (TB). This procedure tests the body’s immune response, indicating whether a person has been infected with Mycobacterium tuberculosis, but it is not a test for active disease. For those who require testing for employment, travel, or exposure, understanding where to get the test is essential.
Understanding the Tuberculin Skin Test
The primary purpose of the Mantoux test is to detect a latent TB infection (LTBI). This means the TB bacteria are present but dormant, contained by the immune system, and not causing active symptoms or illness. A positive TST result indicates the person has been exposed to the bacteria and developed an immune reaction.
Screening is often required for individuals facing a higher risk of exposure, such as healthcare workers and employees in correctional facilities or nursing homes. Testing is also advised for people who have recently traveled to or lived in countries with high rates of TB infection. Furthermore, contact tracing following a confirmed case of active TB necessitates testing for those in close contact with the infected person.
While the test is a valuable screening tool, it does not distinguish between latent infection and active disease. Therefore, a positive result requires further medical evaluation. Next steps usually involve a medical exam and potentially a chest X-ray to rule out active TB. Interpretation of the results depends heavily on the individual’s specific risk factors for TB exposure.
Locating Testing Sites and Accessibility
Several types of facilities offer the Mantoux test, providing different levels of accessibility and cost. Primary Care Providers (PCPs) are a common and convenient option, allowing the test to be integrated into a patient’s overall continuity of care. Scheduling an appointment with a family doctor or internist is often the first choice for those with established healthcare.
Public Health Departments are excellent resources, frequently offering the test at a low cost or even free of charge, especially for people who are uninsured or high-risk. These government-operated clinics focus on infectious disease control and have dedicated staff experienced in administering the test. However, their hours may be more restricted than private facilities.
Urgent Care Centers and retail clinics, often found inside pharmacies, provide quick, walk-in access to the TST, which is beneficial for time-sensitive requirements. These locations often have extended hours, making it easier to fit the two-part testing process into a busy schedule. While convenient, the cost at these facilities may be higher than at public health centers.
For employment screening or travel purposes, Occupational Health Clinics and specialized Travel Clinics are good options. Occupational health clinics routinely handle the required two-step TST for new employees in high-risk professions. Travel clinics can bundle the TST with other necessary pre-travel vaccinations and health consultations.
The Administration and Interpretation Process
The Mantoux test involves a precise, two-phase process beginning with the administration of the test solution. A healthcare professional injects a small amount of Purified Protein Derivative (PPD) tuberculin, typically 0.1 mL, into the dermis of the inner forearm. This intradermal injection goes just beneath the outer layer of skin and creates a small, pale, raised bump called a wheal.
The injection site must be left undisturbed, and the patient is required to return to the clinic for the second phase: interpretation. This reading is mandatory and must occur between 48 and 72 hours after the injection to ensure an accurate result. If the reading is not performed within this specific window, the test is invalid, and a new one must be administered.
During the interpretation appointment, the technician visually inspects and then palpates the injection site to measure the size of any firm swelling, known as induration. Only the diameter of this induration, measured in millimeters across the forearm, determines the result; surrounding redness (erythema) is disregarded. The classification of a positive result depends on the patient’s individual risk factors, with induration measurements of 5 mm, 10 mm, or 15 mm serving as different thresholds for a positive reading.
A positive result signals that the immune system has reacted to the PPD, indicating a likely latent TB infection. The next medical step is usually a follow-up evaluation. This may include a chest X-ray or a blood test, such as an Interferon-Gamma Release Assay (IGRA), to determine if the infection is latent or has progressed to active TB disease and ensure the correct treatment is prescribed.