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Mycobacterium tuberculosis Complex by NAAT

Mtb, Acid Fast Bacilli, TB, Mtb Complex, Tubercule, MTB/RIF, Rifampin

Department

Microbiology

Instructions

This test is a component of the AFB Culture and Smear test and is only available for sputum and tracheal aspirate specimens. It is not routinely available for individual orders. Any requests for testing of other types of specimens must be approved by the Microbiology Medical/Technical Director.

Specimen Collection Criteria

Collect: One of the following specimen types in a sterile plastic collection container:

• Sputum (Induced or Expectorated).
• Tracheal Aspirates.

The efficacy of this test has not been demonstrated for the direct detection of M. tuberculosis using other clinical specimens (e.g., blood, bone marrow, urine, CSF, BAL, bronchial washings, stool, solid tissue).

Physician Office/Draw Specimen Preparation

Maintain original specimens refrigerated (2-8°C or 36-46°F) and transport to the Laboratory within 24 hours of collection.

Preparation for Courier Transport

Transport: Sputum and tracheal aspirate specimens, refrigerated (2-8°C or 36-46°F).

Rejection Criteria

• Specimen types other than sputum or tracheal aspirates.
• Unlabeled specimens.
• Grossly bloody specimens.
• Specimens contaminated with food or other solid particles.
• Swab specimens.
• This test will not be performed on previously positive patients more frequently than every 12 months.
• This test will not be performed on previously negative patients more frequently than every 30 days unless prior approval is obtained from the Medical/Technical Director.

Storage

Specimen Stability for Testing:

Original Specimens
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 24 hours
Frozen (-20°C/-4°F or below): Unacceptable

Re-suspended Specimens
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Up to 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak Microbiology Laboratory

Performed

Sunday – Saturday.
Results available within 24 hours. 

Reference Range

Negative.

Test Methodology

Nucleic Acid Amplification (FDA Approved). 

Interpretation

• This test does not differentiate among the members of the M. tuberculosis complex (M. tuberculosis, M. bovis, M. bovis BCG, M. africanum, and M. microti).
• Cross-reactions can occur with M. scrofulaceum if present at a concentration greater than 10⁸ CFU/test.
• A negative result does not rule out MTB infection.
• A positive or indeterminate result for rifampin will be sent to a reference laboratory for confirmation.
• This test is FDA-Approved for smear-positive and smear-negative specimens.

Clinical Utility

To aid in the diagnosis of tuberculosis and in the detection of M. tuberculosis isolates that are resistant to rifampin.

Clinical Disease

Tuberculosis (TB) is caused by Mycobacterium tuberculosis. There are three stages of TB; primary or initial infection, latent or dormant infection, and reactivation TB. Ninety to 95% of primary TB infections are asymptomatic. Patients have a positive tuberculin skin test and a latent or dormant infection. This infection may activate at any age producing clinical TB in whatever organ it inhabits. Approximately 20% of pulmonary TB in adults results from a newly acquired infection, the rest of the cases are due to reactivation of a previously acquired infection. The general symptoms of tuberculosis are: unexplained weight loss, loss of appetite, night sweats, fever, fatigue, and chills. The symptoms of tuberculosis of the lungs include: coughing for 3 weeks or longer, hemoptysis (coughing up blood), and chest pain. Other symptoms depend on the area of the body that is infected.

Epidemiology

The number of cases varies according to county, age, race, sex, and socioeconomic status. In the U.S. in 2019, 8,920 cases of TB were reported. Worldwide, 10 million people are ill with tuberculosis. TB has been almost eliminated in some segments of the population. It is still prevalent in persons greater 70 years old, and TB is twice as prevalent in blacks as in whites in all age groups. TB has also increased greatly in persons with AIDS. There has been an increase in TB caused by drug-resistant organisms. The incidence of TB is increasing and the likelihood of a steeper rise and outbreaks of drug-resistant organisms appears certain.

Incubation Period

Latent or dormant TB infections usually occur within 1-2 years of initial exposure. TB can develop more easily if the immune system is weakened by malnutrition, AIDS, diabetes, cancer, or following treatment with immunosuppressant drugs.

Transmission

In developed countries, M. tuberculosis is spread through airborne particles that are generated when persons with active pulmonary tuberculosis cough or sneeze. The organisms may remain in the room air for several hours, increasing the chance of infecting people who enter the room during this time.

CPT Codes

87581

Contacts

Last Updated

9/30/2024