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Test ID: SAFB Acid-Fast Smear for Mycobacterium, Varies

Reporting Name

Acid Fast Smear For Mycobacterium

Useful For

Detection of acid-fast bacilli in clinical specimens

Clinical Information

Mycobacterium tuberculosis is a leading infectious disease cause of death worldwide. The Centers for Disease Control and Prevention has reported a rise in the incidence of tuberculosis associated with AIDS, foreign-born cases, and increased transmission in high-risk populations. There has also been a rise in the number of M tuberculosis strains that exhibit resistance to one or more antituberculosis drugs. The public health implications of these facts are considerable. Because M tuberculosis is readily spread by airborne particles, rapid diagnosis and isolation of infected persons is important. Nontuberculous mycobacteria infections also cause significant morbidity and mortality in humans, particularly in immunocompromised persons. Detection of acid-fast bacilli in sputum specimens allows rapid identification of individuals who are likely to be infected with mycobacteria while definitive diagnosis and treatment are pursued.


Patients whose sputum specimens are identified as acid-fast positive should be considered potentially infected with Mycobacterium tuberculosis, pending definitive diagnosis by molecular methods or mycobacterial culture.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
TBT Concentration, Mycobacteria No, (Bill Only) No
TISSR Tissue Processing No, (Bill Only) No

Testing Algorithm

When this test is ordered, the reflex tests may be performed at an additional charge.


See Meningitis/Encephalitis Panel Algorithm in Special Instructions.

Report Available

1 day

Day(s) Performed

Monday through Sunday

Clinical Reference

1. American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America: Controlling Tuberculosis in the United States. Am J Respir Crit Care Med. 2005;172:1169-1227

2. American Thoracic Society: An Official ATS/IDSA Statement: Diagnosis, Treatment, and Prevention of Nontuberculous Mycobacterial Diseases. Am J Respir Crit Care Med. 2007;175:367-416

Method Name

Auramine-Rhodamine Stain

Specimen Type


Ordering Guidance

For the preferred test for rapid, direct detection of Mycobacterium tuberculosis from clinical specimens, order MTBRP / Mycobacterium tuberculosis Complex, Molecular Detection, PCR, Varies.

Necessary Information

Specimen source is required.

Specimen Required

Submit only 1 of the following specimens:


Specimen Type: Body fluid

Container/Tube: Sterile container

Specimen Volume: 1 mL


Specimen Type: Bone marrow

Container/Tube: SPS/Isolator System or green top (lithium heparin)

Specimen Volume: Entire collection


Specimen Type: Gastric washing

Container/Tube: Sterile container

Specimen Volume: 10 mL

Collection Instructions: Neutralize specimen within 4 hours of collection with 100 mg of sodium carbonate per 5 to 10 mL of gastric wash.


Specimen Type: Respiratory

Sources: Bronchoalveolar lavage fluid, bronchial washing, sputum

Container/Tube: Sterile container

Specimen Volume: 4 mL

Collection Instructions: Collect 3 respiratory specimens for acid-fast smears and culture in patients with clinical and chest X-ray findings compatible with tuberculosis. These 3 specimens should be collected at 8- to 24-hour intervals (24 hours when possible) and should include at least 1 first-morning specimen.


Specimen Type: Stool

Supplies: Stool Collection Kit, Random (T635)

Container/Tube: Sterile container

Specimen Volume: 5-10 g


Specimen Type: Tissue

Container/Tube: Sterile container

Specimen Volume: 5-10 mm

Collection Instructions: Collect a fresh tissue specimen.


Specimen Type: Urine

Container/Tube: Sterile container

Specimen Volume: 2 mL

Collection Instructions: Collect a random urine specimen.


Specimen Type: Swab

Additional Information: Fresh tissue or body fluid is the preferred specimen type instead of a swab specimen. Recovery of mycobacteria and aerobic actinomycetes from swabs is variable.


Sources: Wound, tissue, or body fluid

Container/Tube: Culture transport swab (noncharcoal) Culturette

Specimen Volume: Adequate specimen

Collection Instructions:

1. Before collecting specimen, wipe away any excessive amount of secretion and discharge, if appropriate.

2. Obtain secretions or fluid from source with sterile swab.

3. If smear and culture are requested or both a bacterial culture and mycobacterial culture are requested, collect a second swab to maximize test sensitivity.

Specimen Minimum Volume

Body fluid: 0.5 mL
Respiratory specimen: 3 mL
Fresh tissue: pea-sized piece

If a mycobacterial culture is also requested:
Body fluid: 1.5 mL
Respiratory specimen: 3 mL
Fresh tissue: pea-sized piece

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Refrigerated (preferred) 7 days
  Ambient  7 days

Reference Values

Negative (reported as positive or negative)

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


87176-Tissue processing (if appropriate)

87015-Mycobacteria culture, concentration (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
SAFB Acid Fast Smear For Mycobacterium 676-7


Result ID Test Result Name Result LOINC Value
SAFB Acid Fast Smear For Mycobacterium 676-7


If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Microbiology Test Request (T244)

-General Request (T239)

Mayo Clinic Laboratories | Neurology Catalog Additional Information:

mml-CNS-Infections, mml-Pediatric