Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



Acid-Fast Culture; Culture, AFB; Culture, TB; TB Culture; Mycobacteria Culture

CPT Codes:

87116 – Culture, tubercle or other acid-fast bacilli any source, with isolation and presumptive identifications of isolates
87206 – Smear, primary source with interpretation; fluorescent and/or acid fast stain for bacteria, fungi, parasites, viruses or cell types

Test Includes:

Smear and culture for acid-fast bacilli, identification, and drug resistance studies when appropriate. Refer to Blood Culture, Acid-Fast for blood and bone marrow specimens. All positive results are reported immediately by phone to the physician or patient’s nurse.


Lab Testing Sections:


Referred to:

Minnesota Department of Health (MDH)

Phone Numbers:

MIN Lab: 612-813-5866

STP Lab: 651-220-6555

Test Availability:

Monday - Friday

Turnaround Time:

AFB smears are reported within 24 hours. Positive cultures are reported when detected, negative cultures in 8 weeks.

Special Instructions:

Specific site and date/time of collection are required for specimen processing. Do not submit specimens on swabs. Negative results from swab specimens are unreliable.


Specimen Type:

NOTE: Swab specimens are unacceptable for AFB culture.

Specimens may include aspirates (abscess); body fluids, bronchial wash, CSF, gastric aspiration, skin, sputum, tissue, urine, and stool. Refer to Blood Culture, AFB for blood and for bone marrow specimens


Sterile container


See Collection


Specimen Type


Special Instructions

Aspirate, Abscess

As much as possible

Collect aseptically. Remove needle and cap syringe with sterile Luer cap before transport.

Body Fluids

>1 mL

Collect aseptically, using SPS (yellow top) tubes for bloody specimens.


As much as possible

Collect aseptically.

Blood/Bone marrow

<14 yr: >1 mL
>14 yr: >5 mL

Bone marrow:
1-3 mL

Refer to Blood Culture, AFB for additional information. Isolator™ 10 mL tube (blood) or Isolator™ 1.5 mL tube (bone marrow). Do not refrigerate

Bronchial wash

<14 yr: >1 mL

>14 yr: >5 mL

Avoid contaminating bronchoscope with tap water.


>1 mL

Aseptic collection.

Gastric Fluid

5 - 15 mL

Collect early morning specimen before patient has eaten.

1. Introduce nasogastric tube orally or nasally into stomach
Perform lavage with 20-30 mL of sterile, distilled water.
Recover specimen and place in sterile, leakproof container.
Before removing tube, release suction and clamp it.
In lab, each 35-50 mL of gastric washings of the specimen will be neutralized with 1.5 mL of sodium bicarbonate within 1 hour of collection. Refrigerate.
Three specimens collected on three successive days are desirable.


As much as possible

Collect as follows:
Cleanse collection site with 70% alcohol. Allow to dry.
Submit biopsy material.
Please note if infection was acquired in a foreign country.


5 - 10 mL

Collect from an early morning, deep cough on at least 3 consecutive days. For follow-up of patients on therapy, collect at weekly intervals beginning 3 weeks after initiation of therapy. Do not pool specimens. Optimal specimens have a PMN to squamous epithelial cell ratio of >2:1.

1. Have patient rinse or gargle with water.
Instruct patient to cough deeply to produce a lower respiratory tract specimen. Collect in sterile container.
For pediatric patients unable to produce sputum, respiratory therapist should collect via suction.


1 - 5 gm

Collect specimen directly into a leakproof container not contaminated with urine, residual soap, or disinfectants.


1 gm

Aseptic collection.


Child: 10 mL

>14 yr: 40 mL

Collect first morning specimen. 24-hour pooled specimens are not acceptable.

Catheterized specimen: Straight Catheter

1. Thoroughly cleanse the urethral area with povidone - iodine and water.
Aseptically insert catheter into the bladder.
Allow ~10 mL to pass, then collect 1 - 10 mL into a sterile tube.
After urine is collected, pull catheter out of the cap of the tube, tighten cap, and depress spout.
Transport to the lab within 30 minutes of collection.

Clean-catch, Mid-stream specimen:


1. Clean glans with soap and water.
Rinse area with wet gauze pads.
While holding foreskin retracted, begin voiding.
After several mL have passed, collect midstream portion without stopping flow of urine.
Transfer specimen to a leak-proof sterile container.


1. Thoroughly clean urethral area with soap and water.
Rinse area with wet gauze pads.
While holding labia apart, begin voiding.
After several mL have passed, collect midstream portion without stopping flow of urine.
Transfer specimen to a sterile leak-proof container.

Special Processing:

● Refrigerate all specimens for mycobacterial culture except blood and bone marrow.
● Lab will neutralize gastric fluid specimens within one hour of collection.
● Specimens are transported from Children’s lab to MDH, Monday-Saturday by courier.


Onsite collections: Transport to the Laboratory immediately.

Offsite collections:
Specimens must be promptly transported to the laboratory, with the next available courier, not to exceed 24 hours from the time of collection.

Sample Rejection:

Specimen received on a swab; improperly labeled specimen; specimens with prolonged transit time (see Transport/Storage) specimen not submitted in appropriate transport container; insufficient volume; external contamination; 24-hour urine collections; 24-hour sputum collections; insufficient volume. If an unacceptable specimen is received, the physician or nursing station will be notified and another specimen requested before the specimen is discarded.


Reference Range:

No mycobacteria isolated.

Critical Values:

Positive AFB smears and cultures will be called to the physician or patient’s nurse.


Negative results are unreliable on specimens obtained on swabs.


Auramine-Rhodamine stain and BBL MGIT Mycobacteria system


Cook, JH, and M Pezzlo (1992). Specimen receipt and accessioning. Section 1. Aerobic bacteriology, 1.2.1-4. In HD Isenberg (ed) Clinical Microbiology Procedures Handbook. American Society for Microbiology, Washington DC

Miller, J Michael (1999) A Guide To Specimen Management in Clinical Microbiology, American Society for Microbiology, Washington DC

Miller, J Michael, and HT Holmes (1999) Specimen Collection, Transport, and Storage In PR Murray et al, (ed), Manual of Clinical Microbiology, 7th edition, American Society for Microbiology, Washington DC, pp 33-104

Updated MDH Specimen Requirements for Acid Fast Bacilli (AFB) (10/29/2010)


10/15/2012: Removed notification to Infection Prevention on positive results.
2/28/2013: Swab specimens are not acceptable info added.
11/10/2014: Offsite collections added.

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