Lab Test

Culture, AFB

Mycobacteria, MAC (Mycobacterium avium complex), AFB (Acid Fast Bacilli), TB (tuberculosis), MAI (Mycoacterium avium-intracellulare), MOTT (Mycobacterium other than tuberculosis), NTM, Rapid grower AFB, AFB Culture, AFB Stain, AFB Smear, Tuberculosis smear (TB smear), Mtb

Test Codes

Stain: EPIC: LAB5535, Culture: EPIC: LAB5475

Specimen Collection Criteria

Collect: Obtain at least one of the following specimen types as described below, before beginning antimycobacterial therapy.

  • Abscess, Skin Lesions, Wounds: Clean skin with isopropyl alcohol. Collect aspirate fluid from periphery and submit in a sterile, non-leaking collection container.
  • Blood (Immunocompromised Patients): One 10 mL (adult) Isolator tube (preferred) or one 1.5 mL (pediatric) Isolator tube.
  • Bone Marrow:
    • Preferred specimen: Bone marrow in a pediatric Isolator tube [1.5 mL lysis centrifugation (Isolator) tube].
    • Also acceptable: If the pediatric Isolator tube is unavailable the following tubes are acceptable:
      • Sterile tubes containing SPS:
        • Can be used for bacterial, fungal, and mycobacterial culture.
        • Fastidious organisms such as Streptococcus pneumoniae may be inhibited from growth.
      • Sterile tubes containing Lithium or Sodium Heparin:
        • Can be used for fungal and mycobacterial cultures.
        • Can not be used for bacterial culture.
      • Sterile, screw-capped tubes (not recommended):
        • Can be used for bacterial, fungal, and mycobacterial cultures.
        • Bone marrow will clot and will need to be ground prior to culture. This may adversely affect the ability to recover microorganisms (especially fungi).
  • Cutaneous Ulcers: Collect biopsy material from the edge of the ulcer and place in a sterile, non-leaking collection container.
  • Gastric Aspirates: Submit in a sterile, non-leaking collection container.
  • Respiratory Tract Specimens (Bronchial Washings, Bronchial Brushes, BAL): Submit in a sterile, non-leaking collection container.
  • Sputum: 2-3 consecutive individual specimens may be collected within an 8-24 hour interval and placed in sterile, non-leaking collection containers. Collect deep cough specimens. At least one of these should be an early morning specimen. Do NOT submit saliva. Specify whether the specimen is induced or expectorated, since induced sputum specimens resemble saliva. Sputum is the usual specimen collected for the diagnosis of tuberculosis. (Minimum Volume: 3-5 mL per specimen.)
  • Sterile Body Fluids: Submit in a sterile, non-leaking collection container.
  • Stool (Immunocompromised Patients): Collect random stool specimen in a sterile, non-leaking collection container. (Minimum 1.0 g)
  • Tissue: Submit in a sterile, non-leaking collection container.
  • Urine: First-morning void urine specimen. Submit 40 mL each day for three consecutive days, into sterile, non-leaking collection containers.

**Excised tissue can be sent in ESwab transport container.

**Using a swab to collect specimen for AFB culture is not acceptable and will be cancelled.

Transport each specimen to the Laboratory immediately after collection.

Physician Office/Draw Specimen Preparation

  • Arrange for transportation to the Laboratory prior to specimen collection.
  • Maintain each specimen (except Isolator tubes) individually refrigerated (2-8°C or 36-46°F) prior to transport.
  • Isolator tubes must be stored at room temperature (20-26°C or 68-78.8°F).

Preparation for Courier Transport

Transport: All specimen types (except Isolator tubes) in the described appropriate container, refrigerated (2-8°C or 36-46°F). Isolator tubes must be transported at room temperature (20-26°C or 68-78.8°F).

Rejection Criteria

  • Swab specimens.
  • Saliva.
  • Containers with grossly contaminated exteriors.
  • Improperly collected (e.g., formalin, wax containers) specimens or specimens in a container that has ever contained formalin.
  • Improperly stored specimens.
  • 24 hour urine specimens.
  • Catheter-bag specimens.
  • Isolator tubes received refrigerated or frozen.

Inpatient Specimen Preparation

  • Deliver each specimen to the Laboratory immediately after collection.
  • Isolator tubes must be kept at room temperature (20-26°C or 68-78.8°F).

In-Lab Processing

Gastric aspirates must be sent immediately to the Microbiology Laboratory to be neutralized.

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 1 hour (Isolator tubes: 16 hours)
Refrigerated (2-8°C or 36-46°F): 8 hours (Isolator tubes are unacceptable refrigerated)
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 30 days

Laboratory

Dearborn Microbiology Laboratory
Taylor, Trenton and Wayne sent to Dearborn Microbiology Laboratory for testing.

Royal Oak Microbiology Laboratory
Farmington Hills, Grosse Pointe, and Troy sent to Royal Oak Microbiology Laboratory for testing.

Performed

Sunday – Saturday.
Smear results available within 24 hours of receipt in the Royal Oak Microbiology Laboratory.
Results available in 6 weeks for negative culture.

Reference Range

No Acid Fast Bacilli recovered.

Test Methodology

Broth and Agar culture, Acid Fast stain. The M. tuberculosis Complex by NAAT test will be performed on at least one sputum or tracheal aspirate specimen per patient.

Interpretation

  • Isolation of Mycobacterium species by culture from sputum, pleural fluid, early-morning gastric aspirates, urine, cerebrospinal fluid (CSF), or other body fluids establishes the diagnosis. In a young child, the best culture material for the diagnosis of pulmonary tuberculosis is usually an early-morning gastric aspirate.
  • M. tuberculosis is a slowly-growing microorganism. Recovery may take as long as 2 to 3 weeks by the automated broth method. Even with optimal culture techniques, the organism is isolated from fewer than 50% of children with pulmonary tuberculosis. Rapid identification of M. tuberculosis in the laboratory utilizes DNA probes on growth from culture. Attempts are made to demonstrate AFB in sputum and other specimens by microscopy and by molecular techniques (1).
  • Note: MDHHS uses both conventional 7H10 agar and broth methods for susceptibility testing of M. tuberculosis. Mycobacterial organisms other than M. tuberculosis are forwarded to the Advanced Diagnostics Laboratory, National Jewish Hospital, Denver, CO, for susceptibility testing by request only.
  • Note: Susceptibility testing is ordered by the Send Out Laboratory. The isolate is handled by the Microbiology Laboratory.

Clinical Utility

This test aids in the diagnosis of tuberculosis. Isolation of M. tuberculosis is always considered significant. Isolation of other species of Mycobacterium may be significant.

Clinical Disease

Tuberculosis (TB) is a disease caused by M. tuberculosis and M. bovis. It primarily affects the lungs, but can disseminate to every organ system. TB remains a global health issue. Per the World Health Organization, it is the leading cause of death produced by a single infectious agent. M. tuberculosis affects 1.7 billion people worldwide and causes three million deaths per year.

Epidemiology

Case rates of tuberculosis for all ages are highest in urban, low-income areas, and in nonwhite racial and ethnic groups, among whom more than two thirds of reported cases in the United States now occur. Foreign-born persons account for more than 40% of cases. Specific groups with the highest rates of infection and disease are minority groups, the homeless, and residents of correctional facilities. Although infected children of all ages are at increased risk for developing tuberculous disease, infants and post-pubertal adolescents are at highest risk in the United States. Other risk factors for progression of infection to disease include recent close contact with an infected person; recent skin test conversion; immunodeficiency, particularly that caused by HIV infection; intravenous drug use; certain diseases and medical conditions, specifically Hodgkin's disease, lymphoma, diabetes mellitus, chronic renal failure, malnutrition, and immunosuppression induced by drugs (1).

Incubation Period

The incubation period from infection to development of a positive reaction to a tuberculin skin test is about 2 to 10 weeks. The risk for developing disease is highest in the first 2 years after infection. However, months to years may elapse between infection and disease. In most instances, untreated infection becomes dormant and never progresses to clinical disease in the healthy host (1).

Transmission

  • Transmission of tuberculosis is usually by inhalation of droplet nuclei produced by an adult or adolescent with infectious pulmonary tuberculosis. The duration of infectivity of an adult receiving effective treatment depends on the antimycobacterial susceptibility of the organism, the degree of sputum acid-fast smear positively and cough frequency. Although infectivity usually lasts only a few weeks, it may persist for a longer time, especially if the adult patient is nonadherent with medical therapy or is infected with a resistant isolate. If the sputum is negative on repeated smears and if the cough has disappeared, the person is considered noninfectious. The majority of adult and adolescent patients are considered to be noninfectious within a few weeks of starting appropriate therapy to which the infecting organism is susceptible. Children with primary pulmonary tuberculosis are usually not contagious because their lesions are small, discharge of bacilli is minimal, and cough is minimal or nonexistent.
  • The portal of entry is usually the respiratory tract. Skin, gastrointestinal tract, and mucous membranes have been implicated in a few cases. On rare occasions, tuberculosis is transmitted from mother to fetus transplacentally or by infected amniotic fluid (1).

Reference

  1. Conville, P.S., F.G. Witebsky, 2015. Mycobacterium: General Characteristics, Laboratory Detection, and Staining Procedures. Jorgensen, J.H., et.al., Manual of Clinical Microbiology, 11th ed., American Society for Microbiology, Washington, D.C.; p.472-502

CPT Codes

87116, 87206, 87556. Additional CPT codes will be incurred when the culture is positive. Depending on specimen type, 87015 will be incurred.
LOINC:  543-9

Contacts

Last Updated

9/16/2021

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