How is TB diagnosed?
There are two kinds of tests that can be used to help detect TB infection - the TB blood test and the TB skin test. A positive TB blood test or TB skin test only tells that a person has been infected with TB bacteria. It does not tell whether or not the person has progressed to TB disease. Other tests, such as a chest X-ray and a sample of sputum, are needed to see whether the person has TB disease.
Who should get a TB test?
You should get tested for TB if:
How Should I Get Tested for TB?
- You have spent time with a person known to have active TB disease or suspected to have active TB disease; or
- You have HIV infection, drink heavily, are an intravenous drug user, or have another condition that weakens the immune system and puts you at high risk for active TB disease; or
- You think you might have active TB disease; or
- You are from a country where active TB disease is very common (most countries in Latin America and the Caribbean, Africa, Asia, Eastern Europe, and Russia); or
- You live somewhere in the United States where active TB disease is more common such as a homeless shelter, migrant farm camp, prison or jail or long-term care facility.
Brown County Public Health Division offers the TB blood test (T-SPOT) and the TB skin test.
TESTS ARE GIVEN BY APPOINTMENT – call 448-6400.
- TB Blood Test: This test is the only TB test with a sensitivity and specificity greater than 95%. Centers for Disease Control and Prevention recommends the T-SPOT®.TB blood test over the TST in all situations requiring TB testing. The TB blood test requires only one trip to the Public Health Division. Results will be sent to you in the mail, typically within 1 week.
- TB Skin Test: Separate appointments are needed for the administration and the reading of the test. Appointments for the administration of TB skin tests are available on Mondays, Tuesdays, Wednesdays and Fridays. The skin test must be read by the Public Health Division staff within 48-72 hours. If the TB skin test is positive, you will be referred to your provider for additional follow-up. (A TB blood test will be needed that same day a skin test is read positive. If not, a 3-6 month interval between the TB skin test and blood test is recommended to prevent a false positive.)
- Two-step TB Skin Tests: Those required to have two-step skin testing need to arrange to come in for two TB skin tests. If the first TB skin test is negative, then a second TB skin test would need to be given 7-21 days after the first test. There is a fee for each TB skin test.
(Most agencies will accept one TB blood test in place of the two-step skin test.)
We accept cash, check or credit/debit card.
|Cost per test:||T-SPOT®.TB Test (T-Spot)||$70.00|
| ||Tuberculin Skin Test (TST)||$20.00|
The TB blood test is covered by Medical Assistance and most insurance companies.
Vaccination with live viruses (i.e., MMR, chickenpox, FluMist) may interfere with the TB test. The TB test can be done on the same day as a live virus vaccine or at least 4 weeks after the administration of the live virus vaccine.
| ||T-SPOT.TB Test||Tuberculin Skin Test|
|A single visit is required||Yes||No; requires at least two visits|
|No return visit for results||Yes||No; requires a return visit for reading in 48-72 hours|
|TB test with high sensitivity||Yes||No; limited sensitivity, especially in the immunosuppressed|
|TB test with high specifcity||Yes||No; limited specificity|
|Does not cross react with most non-tuberculosis mycobacteria||Yes||No; cross reacts with several non-tuberculosis mycobacteria|
|Objective tests results||Yes||No; subjectivity with intrepretation of results|