Tuberculosis (TB) screening is a public health measure designed to identify individuals exposed to the bacteria that cause TB, even without symptoms. This proactive approach helps detect infection early, preventing its spread and ensuring timely treatment. Screening plays a significant role in controlling TB, a bacterial infection that primarily affects the lungs but can also impact other body parts.
Finding a Screening Location
Individuals seeking a TB screening have several accessible options, including local public health clinics, primary care physician’s offices, urgent care centers, and occupational health services. Public health clinics often provide low-cost or free screenings, typically listed on local health department websites.
Primary care physician’s offices can integrate TB screening into routine healthcare. Urgent care centers also offer convenient TB testing without an appointment. For employment or educational requirements, occupational health services or student health centers often conduct screenings. Call ahead to confirm services, costs, and requirements.
Common TB Screening Tests
Two primary methods are used for TB screening: the Tuberculin Skin Test (TST) and Interferon-Gamma Release Assays (IGRAs). The TST, also known as the Mantoux test, involves injecting a small amount of purified protein derivative (PPD) under the skin of the forearm. After 48 to 72 hours, a healthcare professional examines the injection site for a raised, firm bump. The size of this reaction determines the result.
IGRAs are blood tests that measure the immune system’s response to TB bacteria. Examples include QuantiFERON-TB Gold and T-SPOT.TB tests. For an IGRA, a blood sample is drawn, and the results are typically available within 24 to 48 hours, eliminating the need for a return visit. Both TST and IGRAs indicate TB bacteria presence, but do not distinguish between latent infection and active disease.
Understanding Your Results and Next Steps
Once you undergo a TB screening, understanding the results is the next important step. A negative result generally indicates no evidence of TB infection, meaning TB bacteria are unlikely to be present. However, in some cases, further testing may be recommended, especially if you have symptoms of active TB disease, a weakened immune system, or recent exposure to TB.
A positive screening result means you have been exposed to TB bacteria and have them in your body, but it does not necessarily mean you have active TB disease. A positive screening indicates a TB infection, which can be either latent TB infection (LTBI) or active TB disease. With LTBI, bacteria are inactive, cause no symptoms, and cannot spread. Active TB disease means bacteria are multiplying, causing symptoms, and are contagious.
If your screening is positive, a healthcare provider will order additional tests, such as a chest X-ray and sputum tests, to determine if you have active TB disease or latent infection. Follow-up with a healthcare provider is important regardless of the result to ensure appropriate care and management.