Skip to main content

Health Encyclopedia

Search the Health Encyclopedia

Sputum Gram stain

Definition

A sputum Gram stain is a laboratory test used to detect bacteria in a sputum sample. Sputum is the material that comes up from your air passages when you cough very deeply.

The Gram stain method is one of the most commonly used methods to rapidly identify the cause of a bacterial infection, including pneumonia.

Alternative Names

Gram stain of sputum

How the Test is Performed

A sputum sample is needed.

  • You will be asked to cough deeply and spit any substance that comes up from your lungs (sputum) into a special container.
  • You may be asked to breathe in a mist of salty steam. This makes you cough more deeply and produce sputum.
  • If you still do not produce enough sputum, you might have a procedure called bronchoscopy.
  • To increase the accuracy, this test is sometimes done three times, often 3 days in a row.

The sample is sent to a lab. The lab team member places a very thin layer of the sample onto a glass slide. This is called a smear. Stains are placed on the sample. The lab team member looks at the stained slide under a microscope, checking for bacteria and white blood cells. The color, size, and shape of the cells help identify the bacteria.

How to Prepare for the Test

Drinking a lot of fluids the night before the test helps your lungs produce phlegm. It makes the test more accurate if it is done first thing in the morning.

How the Test will Feel

There is no discomfort, unless a bronchoscopy needs to be performed.

Why the Test is Performed

Your health care provider may order this test if you have a persistent or prolonged cough, or if you are coughing up material that has a foul odor or unusual color. The test may also be done if you have other signs and symptoms of respiratory disease or infection.

Normal Results

A normal result means that few to no white blood cells and no bacteria were seen in the sample. The sputum is clear, thin, and odorless.

What Abnormal Results Mean

An abnormal result means that bacteria is seen in the test sample. You may have a bacterial infection. A culture is needed to confirm the diagnosis.

Risks

There are no risks, unless bronchoscopy is performed.

References

Beavis KG, Charnot-Katsikas A. Specimen collection and handling for diagnosis of infectious diseases. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 64.

Torres A, Menendez R, Wunderink RG. Bacterial pneumonia and lung abscess. In: Broaddus VC, Mason RJ, Ernst JD, et al, eds. Murray and Nadel's Textbook of Respiratory Medicine. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 33.

Review Date:11/14/2016
Reviewed By:Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. © 1997-A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

adam.com

The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.

Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.

Health
Outcome Data

No data available for this condition/procedure.

Images

Health Encyclopedia

More Features

We Appreciate Your Feedback!
1. Did you find this information useful?
         Yes
         No
2. Would you recommend this website to family and friends?
         Yes
         No