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:
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:



How it Feels:
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.

Risks:
The risks are minimal and are associated with the method of specimen collection.

Why this Test is Performed:
The test detects infection caused by bacteria. The test is useful in detecting tuberculous infection.

Normal Values:
No bacteria are normally found on the stained specimen.

Abnormal Results:
Abnormal results may indicate an infection.

Cost:
The estimated cost is $32 for laboratory processing of the specimen. Certain types of specimens may require higher processing charges. The cost may be higher if a procedure such as a tissue biopsy , bone marrow biopsy , or aspirate is needed to obtain the specimen.

Special Considerations:
If a tissue biopsy is required for the test, other diagnostic tests may be performed on the same specimen.