A TB test is a screening tool that is used to detect tuberculosis in the body. The Centers for Disease Control and Prevention notes that there are both skin tests and blood tests that can determine if a person has the disease.
The TB skin test involves the injection of a tiny amount of tuberculin fluid beneath the skin. Within 72 hours of injection, a small raised hard area may develop if the person has been infected with TB. The TB blood test is a basic blood test that detects the TB virus. The CDC recommends the blood test for TB for those who may have difficulty returning to have the skin test read by a medical practitioner.