This test attempts to detect and identify organisms in the sputum. Sputum is a secretion coughed up from the lungs. It is different than saliva, which comes from the mouth.
This test is ordered when the healthcare professional suspects an infection in the lungs or bronchi, such as pneumonia or tuberculosis. The bronchi are the tubes that carry air to the lungs. In many cases, sputum will contain the infection-causing organism when a lung infection is present.
The person is asked to cough deeply to bring up sputum. The sputum can then be spit into a cup. The sputum is taken to a lab, where it is placed in special containers. These containers have special chemicals and nutrients to help organisms, such as bacteria, grow. Any bacteria that grow in the containers can be identified.
No preparation is usually needed for this test. Specific instructions will be given if needed.
The results of this test usually take at least 48 hours. In some cases, up to six weeks may be needed to detect certain organisms.
Sometimes, a bad sample is taken, such as when a person simply spits into the cup. It is usually not hard to tell that this has happened, because the sample will grow bacteria that normally live in the throat and mouth but typically do not cause an infection in the lungs.
If organisms are present in a good sputum sample, they are probably responsible for the person's infection. The infection may be in the bronchi or deep in the lungs.
Knowing the exact cause of an infection helps the healthcare professional recommend a specific therapy. For example, if specific bacteria are found, the healthcare professional may want to give the person a specific antibiotic.
In some cases, a person may have received an antibiotic right away, before the test results are available. The healthcare professional may then switch the antibiotic if a specific organism is found.