If people have a positive TB test, other tests can help to show if they have active tuberculosis. In making a diagnosis of active tuberculosis, doctors rely on symptoms and other physical signs, the person's history of exposure to tuberculosis, and x-rays that may show evidence of a tuberculosis infection.
The healthcare provider will also take sputum and other samples to see if the TB bacteria will grow in the lab. If bacteria are growing, this positive culture confirms a tuberculosis diagnosis. Because M. tuberculosis grows very slowly, it can take up to 4 weeks to confirm the diagnosis. An additional 2 to 3 weeks are usually needed to determine which antibiotics to use to treat the disease.