Health Encyclopedia

Sputum stain for mycobacteria

Definition

Sputum stain for mycobacteria is a test to check for a type of bacteria that cause tuberculosis and other kinds of infection.

Alternative Names

Acid fast bacilli stain; AFB stain; Tuberculosis smear; TB smear

How the test is performed

To obtain a sputum sample, you will be asked to cough deeply and spit the substance that comes up from the lungs (sputum) into a container. You may be asked to inhale a mist of salty steam in order to cough more deeply and produce sputum. If you still don't produce enough sputum, you might have a bronchoscopy.

The specimen is spread on a microscope slide. The cells of the specimen are stained with dyes and then examined under the microscope.

If the stain shows mycobacteria, the specimen may be placed in culture media, which encourages them to grow. (Specimens are often cultured even if no mycobacteria are seen, because sometimes the number of organisms is so low that they don't show up with staining, but they eventually grow on the culture medium.)

How to prepare for the test

It can help to drink a lot of fluids the night before the test. It makes the test more accurate if it's 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

The test is performed when the doctor suspects tuberculosis or other Mycobacterium infection.

Normal Values

Results are normal when no mycobacterial organisms are found.

What abnormal results mean

Abnormal results show that the stain is positive for:

Mycobacterium tuberculosis
Mycobacterium avium-intracellular
Other mycobacteria or acid-fast bacteria

What the risks are

There are no risks, unless bronchoscopy is performed.

Special considerations

To increase the accuracy of this test, it is sometimes done three times, often three days in a row.

There are more sophisticated tests that are sometimes used to stain sputum for mycobacteria. Check with your health care provider to see if these are available in the laboratory.

Review Date:7/25/2008
Reviewed By:A.D.A.M. Editorial Team: David Zieve, MD, MHA, Greg Juhn, MTPW, David R. Eltz. Previously reviewed by Arnold L. Lentnek, M.D., Division of Infectious Disease, Kennestone Hospital, Marietta. Review provided by VeriMed Healthcare Network (11/12/2007).

ADAM Quality A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process. A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

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.