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 provider 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 food and other things 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. If a person gives a good sputum sample, it should not contain any organisms. Sometimes, a bad sample is taken, such as when a person simply spits into the cup. This sample may grow bacteria or other organisms, but does not give any useful information. This is because bacteria normally live in the throat and mouth. These bacteria do not usually cause an infection in the lungs.
If organisms are present in a good sputum sample, an infection is often present. The infection may be in the bronchi or deep in the lungs. Knowing the exact cause of an infection helps the healthcare provider advise a specific therapy. For example, if specific bacteria are found, the healthcare provider may want to give the person a specific antibiotic. In some cases, a person is given an antibiotic right away, before the test results are available. The healthcare provider may then switch the antibiotic if a specific organism is found.
Author:David T. Moran, MD
Date Written:
Editor:Keefe, Sandy, RN, MSN
Edit Date:05/22/00
Reviewer:Adam Brochert, MD
Date Reviewed:09/04/01