Medical Content Created by the Faculty of the
Harvard Medical School
You need to cough up a sample of sputum. To be useful for testing, the stuff you cough up has to be from deep within the lungs. If your cough is too shallow or dry, the doctor might ask you to breathe in a saltwater mist through a tube or mask. This mist makes you cough deeply that helps produce an excellent phlegm sample.
The sputum sample is collected in a sterile container. Your doctor may remove a couple drops to put on a slide. The slide is stained with a special solution that colors the bacteria and white blood cells. The doctor may look at the slide under the microscope. More often the sample is sent to the laboratory and technician does the staining and microscopic examination.
The rest of the sputum sample is incubated to grow the bacteria or other germs in it for further testing. This step is called a sputum culture.