Common TB Test Options and Turnaround Times
A tuberculosis (TB) test is a screening tool used to determine if an individual has been infected with Mycobacterium tuberculosis, the bacteria that causes TB. People often need a TB test for various reasons, including requirements for employment, school enrollment, international travel, or after potential exposure in healthcare settings. Finding a testing option that provides timely results is frequently a priority.
There are two primary types of TB tests. The Tuberculin Skin Test (TST), also known as the Mantoux or PPD test, involves injecting a small amount of purified protein derivative (PPD) under the forearm skin. This test requires two visits: an initial injection and a follow-up visit 48 to 72 hours later for a healthcare professional to read the reaction at the injection site. The result is based on the size of any raised, red bump that forms.
Interferon-Gamma Release Assays (IGRAs) are blood tests. Common IGRA tests include QuantiFERON®-TB Gold Plus and T-SPOT.TB®. These tests measure the immune system’s reaction to TB bacteria in a blood sample. Unlike the TST, IGRAs require only one visit for a blood draw, and results are often available within 24 to 48 hours. This single-visit requirement and quicker laboratory processing time make IGRAs a more convenient and faster option.
Where to Find a TB Test
Several types of facilities offer TB testing. Urgent care centers are a common option, often providing walk-in availability and extended hours for quick testing. These centers are equipped to perform both TSTs and blood tests.
Public health departments frequently provide TB testing, sometimes at reduced costs or for free, especially for those who meet certain criteria. It is advisable to call ahead to inquire about appointment availability and specific testing schedules. Primary care physician’s offices also routinely offer TB tests, though securing an appointment may take longer than at an urgent care facility.
Occupational health clinics are another specialized location for TB testing, particularly for employment purposes. Some pharmacies and retail health clinics, such as MinuteClinic locations, have expanded services to include TB testing. To find a suitable location, individuals can use online search engines, check local health department websites, or call their insurance provider for a list of covered testing sites.
Preparing for Your Test and What It Costs
No specific preparation is needed before a TB skin test or a blood test. For the TST, wearing loose-fitting clothing is advisable. It is important to inform the healthcare provider about any prior history of TB infection, previous positive TB test results, or if you have received the Bacillus Calmette-Guérin (BCG) vaccine, as these factors can influence test interpretation.
The cost of a TB test varies based on the testing facility, your insurance coverage, and the type of test administered. Many health insurance plans cover TB testing, but it is recommended to contact your insurance provider beforehand to understand your benefits and potential out-of-pocket expenses. Public health clinics might offer lower-cost or no-cost testing programs, making them a more affordable option for individuals without insurance or with high deductibles.
Interpreting Results and Further Action
A negative TB test result, whether from a skin test or a blood test, indicates no evidence of TB infection. This means your immune system did not react to the TB proteins, suggesting you have not been infected with the Mycobacterium tuberculosis bacteria. For the TST, a negative result means there is no significant induration (hard, raised area) at the injection site after 48 to 72 hours.
A positive result from either a TST or an IGRA indicates exposure to TB bacteria. It is important to understand that a positive screening test does not automatically mean active TB disease. Instead, it suggests the presence of latent TB infection (LTBI), where the bacteria are present in the body but are inactive and not causing symptoms. Further diagnostic steps are required to differentiate between latent infection and active disease.
Following a positive screening test, healthcare providers will recommend additional evaluations, such as a chest X-ray to look for signs of active lung disease and potentially sputum tests to check for active bacteria. Discussing the test results with a healthcare professional is important for proper interpretation and guidance on next steps, which may include treatment for latent TB infection to prevent active disease.