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Sputum Evaluation (and Sputum Induction)

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What is the test?

If your doctor thinks you have pneumonia, he or she might examine a sample of your sputum, the phlegm that you cough out of your lungs, to try to determine what type of bacteria or other infectious agent might be the cause.

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How do I prepare for the test?

Drink plenty of fluids the night before the test; this may help to produce a sample.

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What happens when the test is performed?

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, usually producing an excellent phlegm sample.

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What risks are there from the test?


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Must I do anything special after the test is over?


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How long is it before the result of the test is known?

The technician stains the sputum sample and views it under a microscope. Some of the sample is incubated to grow the bacteria or other germs in it for further testing. This step is called a sputum culture.While some stain results might be available on the day of your test, the culture usually requires several days.

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