Health Encyclopedia

Acid-fast stain

Definition

The acid-fast stain is a laboratory test that determines if a sample of tissue, blood, or other body substance is infected with the bacteria that causes tuberculosis and other illnesses.

How the test is performed

Your health care provider will collect a sample of blood, urine, stool, sputum, bone marrow, or tissue, depending on the location of the suspected infection.

The sample is then sent to a laboratory, where a small amount is placed on a glass slide, stained, and heated. The cells in the sample hold onto the dye. The lab team member washes the slide with an acid solution and applies a different stain.

The bacteria that hold onto the first dye are considered "acid-fast" because they resist the acid wash. This type of bacteria is associated with tuberculosis and other infections.

How to prepare for the test

Preparation depends on how the sample is collected. Your health care provider will tell you how to prepare.

How the test will feel

The amount of discomfort depends on how the sample is collected.

Why the test is performed

The test can tell if you are infected with mycobacteria, the organism that causes tuberculosis and related infections.

Normal Values

A normal result means no acid-fast bacteria were found on the stained sample.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Abnormal results may indicate an infection with an acid-fast bacteria. Acid-fast bacteria include those that cause tuberculosis, nontuberculous infections, and nocardia infections.

What the risks are

Risks depend on how the sample is collected. Ask your health provider to explain the risks and benefits of the medical procedure.

Review Date:12/3/2007
Reviewed By:D. Scott Smith, M.D., MSc, DTM&H, Chief of Infectious Disease & Geographic Medicine, Kaiser Redwood City, CA & Adjunct Assistant Professor, Stanford University. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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.