Acid-fast stain
Key points
- The acid-fast stain is a test used to examine a specimen for the presence of microorganisms, specifically mycobacteria which include the bacteria that cause Tuberculosis.
- Specimens of blood, urine, stool, sputum, bone marrow, or tissue may be collected, depending on the location of the suspected infection.
- Preparation for the test depends on the sample to be collected.
- The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust.
Definition
The acid-fast stain is a test used to examine a specimen for the presence of microorganisms, specifically mycobacteria which include the bacteria that cause Tuberculosis.
How the test is performed
Specimens of blood, urine, stool, sputum, bone marrow, or tissue may be collected, depending on the location of the suspected infection.
The specimen is then sent to a microbiology laboratory for processing. A small amount of the specimen is placed on a microscope slide. A dye is placed on the slide and heated. The cells retain the dye. The slide is then washed with an acid solution, and a counter-stain is applied.
The bacteria that retain the first dye are acid-fast because they resist the acid wash. Bacteria that wash free of the first dye and take the counterstain are nonacid-fast.
How to prepare for the test
Preparation for the test depends on the sample to be collected. There may be special preparation for a blood, urine, or stool collection. A biopsy of an organ or tissue may be indicated for certain types of infection.
Infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For general information regarding how you can prepare your child, see the following topics:
- Infant test or procedure preparation (birth to 1 year)
- Toddler test or procedure preparation (1 to 3 years)
- Preschooler test or procedure preparation (3 to 6 years)
- School age test or procedure preparation (6 to 12 years)
- Adolescent test or procedure preparation (12 to 18 years)
How the test will feel
The amount of discomfort depends on the type of specimen to be collected. A tissue biopsy or aspiration with a needle may be necessary for some tests.
Why the test is performed
The test detects infection caused by mycobacteria. The test is useful in detecting tuberculous infection.
Written and revised by
Andrey Nailor, M.D.
Our doctors write and review articles for accuracy and keep them up to date.
health.am provides general information, not medical advice. Always consult a qualified health professional about your own health.