Acid-fast stain

How the test is performed:

A specimen is collected from you. Blood, urine, stool, sputum, bone marrow, or tissue samples 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 physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

• 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)
• schoolage 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 bacteria. The test is useful in detecting tuberculous infection.