Rapid sputum tests are used to diagnose tuberculosis (TB) when other tests show that a person probably has TB. Rapid sputum tests are also called nucleic acid amplification tests (NAAs).
One of the best ways to diagnose TB is through a sputum culture. A culture uses a sample of mucus from the lungs (sputum) that is placed under special conditions that allow TB bacteria to grow. If TB bacteria grow, then the person has tuberculosis. The test also can show if a lung infection is caused by some other kind of bacteria. But a sputum culture can take 1 to 8 weeks to provide results.