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Sputum Cytology

Test Overview

Sputum cytology examines a sample of sputum (mucus) under a microscope to determine whether abnormal cells are present. Sputum is not the same as saliva. Sputum is produced in the lungs and in the airways leading to the lungs. Sputum has some normal lung cells in it. See a picture of the lungs' airways.

Sputum cytology may be done to help detect certain noncancerous lung conditions. It may also be done when lung cancer is suspected.

A sputum sample may be collected:

  • By a person coughing up mucus.
  • By breathing in a saltwater (saline) mist and then coughing.
  • During bronchoscopy, which uses a bronchoscope to look at the throat and airway.

Why It Is Done

Sputum cytology is done to find:

  • Lung cancer. But sputum cytology is not used as a screening test for people at risk for developing lung cancer, such as smokers.
  • Noncancerous lung conditions, such as pneumonia or inflammatory diseases, tuberculosis, or the buildup of asbestos fibers in the lungs (asbestosis).

How To Prepare

Home or office sample

No special preparation is required if the sputum sample is to be collected at home or in your doctor's office.

Bronchoscopy sample

Before you have a bronchoscopy to collect a sputum sample, tell your doctor if you:

  • Are taking any medicines.
  • Have allergies to any medicines, including anesthetics.
  • Have any bleeding problems or take blood thinners, such as aspirin, warfarin (Coumadin), or clopidogrel (Plavix).
  • Are or might be pregnant.

For a bronchoscopy, you will also be asked to sign a consent form. Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

Your doctor will tell you how soon before the procedure to stop eating and drinking. Follow the instructions exactly about when to stop eating and drinking, or your surgery may be canceled. If your doctor has instructed you to take your medicines on the day of surgery, please do so using only a sip of water.

Arrange to have someone drive you home after the procedure.

How It Is Done

Home or office sample

Three sputum samples are usually collected over 3 days. Your doctor will give you a container to collect the sputum. This container may have a small amount of liquid (called fixative) in it. The fixative helps preserve the sample. Do not drink this liquid.

For best results, collect the sample in the morning right after waking up. Follow these steps:

  • If you wear dentures, remove them before collecting the sample.
  • Rinse your mouth with water.
  • Take about four deep breaths followed by a few short coughs, then inhale deeply and cough forcefully into the container. Sputum is not the same as saliva, so make sure to get a sample of mucus from deep in your airway.

Carefully follow your doctor's instructions about where to deliver the sample. You may be instructed to take the sample to the doctor's office or to a laboratory. Deliver the sample soon after you obtain it. You may be instructed to refrigerate the sample if you are unable to deliver it immediately.

Bronchoscopy sample

See the topic Bronchoscopy for detailed information on how this procedure is done.

How It Feels

If you have discomfort when taking a deep breath or coughing, getting a sputum sample may be uncomfortable.

For information on how a bronchoscopy procedure feels, see the medical test Bronchoscopy.

Risks

Home or office sample

There is no risk linked with collecting a sputum sample at home or at your doctor's office.

Bronchoscopy sample

Bronchoscopy is generally a safe procedure. Although complications are rare, you should discuss the risks in your particular case with your doctor. Complications that may occur include:

  • Spasms of the bronchial tubes. These can impair breathing.
  • Irregular heart rhythms (arrhythmias).
  • Infection, such as pneumonia. These usually can be treated with antibiotics.

Results

Sputum cytology examines a sample of sputum (mucus) under a microscope to determine whether abnormal cells are present. It may take several days to receive results from a sputum cytology.

Sputum cytology
Normal:

Normal lung cells are present in the sputum sample.
Abnormal:

Abnormal cells are present in the sputum sample.

Abnormal cells may indicate lung conditions such as pneumonia, inflammation, the buildup of asbestos fibers in the lungs (asbestosis), or lung cancer.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include a sample that is too small; is dried out; contains only saliva; or is from nasal secretions, not your airway.

What To Think About

  • There is a chance of false-negative test results with sputum cytology. This means that the test shows a lung condition is not present when it actually is present. Follow-up testing may need to be done if your symptoms continue.
  • Sputum is not the same as saliva. It is important to obtain a sputum sample from deep in your airway. Collecting the sample in the morning, when you first wake up, is generally best.
  • If you have trouble obtaining a good sample, try taking a hot shower first to help loosen the mucus in your airway.
  • A sputum culture is a test to find and identify bacteria or fungi that are infecting the lungs or breathing passages. It is also done to identify the best antibiotic to treat a lung infection. For more information, see the topic Sputum Culture.
  • Bronchoscopy or a needle lung biopsy are more commonly used than sputum cytology because the results provide more information about airway problems. For more information, see the topics Bronchoscopy and Lung Biopsy.

References

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.

Credits

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology
Last Revised March 18, 2011

Last Revised: March 18, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology

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