Routine sputum culture is a laboratory test that looks for germs that cause infection. Sputum is the material that comes up from air passages when you cough deeply.
How the Test is Performed
A sputum sample is needed. You will be asked to cough deeply and spit any phlegm that comes up from your lungs into a special container. The sample is sent to a lab. There, it is placed in a special dish (culture). It is then watched to see if bacteria or other disease-causing germs grow.
How to Prepare for the Test
Drinking a lot of water and other fluids the night before the test may make it easier to cough up the sputum.
How the Test will Feel
You will need to cough. Sometimes the health care provider will tap on your chest to loosen deep sputum. Or, you may be asked to inhale a steamlike mist to help you cough up the sputum. You may have some discomfort from having to cough deeply.
Why the Test is Performed
The test helps identify the bacteria or other type of germs that are causing an infection in the lungs or airways (bronchi).
In a normal sputum sample there will be no disease-causing germs.
What Abnormal Results Mean
If the sputum sample is abnormal, the results are called "positive." Identifying the bacteria, fungus, or virus may help diagnose the cause of:
There are no risks with this test.
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Chernecky CC, Berger BJ. Culture, routine. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:409-411.
Ellison RT, Donowitz GR. Acute pneumonia. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 69.
Review Date 11/20/2017
Updated by: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.