Brief Description

Acid- Fast Bacilli (AFB) smear and culture are two separate tests always performed together at the MSPHL, Tuberculosis (TB) Unit. AFB smear refers to the microscopic examination of a fluorochrome stain of a clinical specimen. The AFB culture is the inoculation of a clinical specimen onto culture media Becton-Dickinson Mycobacteria Growth Indicator Tube (B-D MGIT broth) and Lowenstein-Jensen (L-J) media slant, incubation at 37°C for up to six (6) weeks and detection of growth or no growth during this incubation period.

Laboratory Unit



AFB smear - fluorochrome staining

AFB culture - B-D MGIT system and conventional culture media.

Specimen Collection


  • An early morning, deep cough specimen collected on three (3) consecutive days is best for initial diagnosis of tuberculosis
  • If sputa are collected within the same 24-hour period, a minimum of eight (8) hours between specimens is required
  • Minimum acceptable specimen volume is two (2) mL
  • Ship specimens each day collected to facilitate rapid diagnosis; do not hold until three (3) specimens are collected
  • Refrigerate until shipped

Bronchial Washing:

  • Preferred minimum acceptable volume is two (2) mL
  • Refrigerate until shipped

Pleural Fluid:

  • Preferred minimum volume is two (2) mL
  • Refrigerate until shipped


Submit clinical specimens using the TB Category B carrier provided by the MSPHL in accordance with the Infectious Substance, Category B shipping guidelines.

Acceptable Specimen Type(s)

Bronchial Washing
Pleural Fluid

Test Request Form(s)

Possible Results

AFB Smear:  
1+ (Rare)
2+ (Few)
3+ (Moderate)
4+ (Many)
AFB Not Found
Smear Not Performed

AFB Culture: 
Identification of Mycobacteria species
No growth of Mycobacteria after 6 weeks

Unacceptable Conditions

Specimens that are not labeled with the patient name or identifier.

Clinical specimen collected within eight hours of previous specimen.

Clinical specimen received greater than three (3) days from collection.

Specimen leaking on arrival.

Insufficient specimen volume (less than 2 mL).

Interfering Substances


Result Reported

AFB smears are reported within 24 hours of receipt; AFB cultures are reported: (1) at 6 weeks when no growth occurs or (2) when growth occurs and identification is made.


$48 charge – Private healthcare submitters

CPT Codes



AFB Smear:  676-7

AFB Culture:  543-9

Additional Information