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Sputum stain for mycobacteria is a test to check for a type of bacteria that cause tuberculosis and other infections.
Acid fast bacilli stain; AFB stain; Tuberculosis smear; TB smear
This test requires a sample of sputum.
The test sample is examined under a microscope. Another test, called a culture, is done to confirm the results. A culture test takes a few days to get results. This sputum test can give your doctor a quick, early answer.
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.
There is no discomfort, unless a bronchoscopy needs to be performed.
The test is performed when the doctor suspects tuberculosis or other Mycobacterium infection.
Results are normal when no mycobacterial organisms are found.
Abnormal results show that the stain is positive for:
There are no risks, unless bronchoscopy is performed.
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.
Septimus EJ. Pleural effusion and empyema.In: Mandell GL, Bennett JE, Dolin R, eds.Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 65.
Murray PR, Witebsky FG. The clinician and the microbiology laboratory. In: Mandell GL, Bennett JE, Dolin R, eds.Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 17.