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Sputum stain for mycobacteria

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

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

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Sputum test

How the Test is Performed

This test requires a sample of sputum. 

The test sample is examined under a microscope. This sputum stain test can give your doctor a quick answer. Another test, called a culture, is done to confirm the results. A culture test may take several weeks to get results. 

How to Prepare for the Test

Drinking 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.

If you are having a bronchoscopy, follow your health care provider's instructions on how to prepare for the procedure.

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 Results

Results are normal when no mycobacterial organisms are found.

What Abnormal Results Mean

Abnormal results show that the stain is positive for:

Risks

There are no risks with this test, unless bronchoscopy is performed.


Related Information

Pulmonary tuberculosis

References

Hopewell PC, Kato-Maeda M, Ernst JD. Tuberculosis. 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 35.

Woods GL. Mycobacteria. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 61.

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Review Date: 12/24/2020  

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.

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