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Test ID: MTBT Mycobacterium tuberculosis Complex, Molecular Detection, PCR, Paraffin, Tissue

Useful For

Preferred method for rapid detection of Mycobacterium tuberculosis complex DNA in formalin-fixed, paraffin-embedded tissue specimens

 

Detection of M tuberculosis complex

 

The PCR assay is not intended for the detection of latent tuberculosis and must not be used as a substitute for tests intended for detection of latent tuberculosis such as the tuberculin skin test (TST/PPD) or an interferon gamma release assay (IGRA).

Method Name

Real-Time Polymerase Chain Reaction (PCR)

Reporting Name

MTB complex PCR, FFPE

Specimen Type

Tissue, Paraffin


Necessary Information


Specimen source is required.



Specimen Required


The high sensitivity of amplification by PCR requires the specimen to be processed in an environment in which contamination of the specimen by Mycobacterium tuberculosis DNA is unlikely.

 

Preferred Paraffin-embedded tissue block:

Supplies: Tissue Block Container (T553)

Specimen Type: Formalin-fixed, paraffin-embedded tissue block (FFPE)

Sources: Body tissue

Container/Tube: Tissue block

Collection Instructions: Submit a formalin-fixed, paraffin-embedded tissue block to be cut and returned.

 

Acceptable Paraffin-embedded tissue block:

Specimen Type: Formalin-fixed, paraffin-embedded tissue block (FFPE)

Sources: Body tissue

Container/Tube: Sterile container for each individual cut section (scroll).

Collection Instructions: Perform microtomy and prepare five separate 10-micron sections. Each section (scroll) must be placed in a separate sterile container for submission.


Specimen Minimum Volume

See Specimen Required.

Specimen Stability Information

Specimen Type Temperature Time Special Container
Tissue, Paraffin Ambient (preferred)
  Refrigerated 

Clinical Information

Each year, Mycobacterium tuberculosis accounts for approximately 1.4 million deaths and is responsible for 9 million newly diagnosed cases of tuberculosis worldwide. M tuberculosis is spread from person-to-person via respiratory transmission, and has the potential to become resistant to many or all of the antibiotics currently used if antimycobacterial treatment is not promptly initiated. Therefore, rapid and accurate detection of M tuberculosis in patient specimens is of clinical and public health importance.

 

Conventional culture methods can generally detect M tuberculosis in 2 to 3 weeks, although up to 8 weeks of incubation may be required in some instances. Developed at Mayo Clinic, this rapid PCR assay detects M tuberculosis complex DNA directly from respiratory specimens and other specimens without waiting for growth in culture and, therefore, the results are available the same day the specimen is received in the laboratory. A mycobacterial culture should always be performed in addition to the PCR assay. This assay is rapid but the culture has increased sensitivity over it. The PCR assay targets a unique sequence within the katG gene, which is present in members of the M tuberculosis complex. In addition, the assay can detect genotypic resistance to isoniazid mediated by variants in the katG target, when present.

Reference Values

Not applicable

Interpretation

A positive result indicates the presence of Mycobacterium tuberculosis complex DNA. Members of the M tuberculosis complex detected by this assay include M tuberculosis, M bovis, M bovis bacillus Calmette-Guerin (BCG), M africanum, M canettii, and M microti. The other species within the M tuberculosis complex (eg, M caprae, M pinnipedii, and M mungi) should, in theory, be detected using the primer and probe sequences in this assay, but they have not been tested at this time. This assay method does not distinguish between the species of the M tuberculosis complex.

 

A negative result indicates the absence of detectable M tuberculosis complex DNA.

 

Isoniazid (INH) resistance mediated through a katG variant will be reported when observed but lack of a katG variant does not imply that the isolate is susceptible to INH. There are other genetic loci in addition to katG that can contribute to resistance for this drug.

 

An inhibition result indicates that inhibitors are present in the specimen that could prevent the detection of M tuberculosis DNA. A new specimen can be resubmitted under a new order, if desired.

Clinical Reference

1. Iseman MD: A clinician's guide to tuberculosis. Second edition. Philadelphia, PA. Lippincott Williams and Wilkins, 2013

2. Centers for Disease Control and Prevention: Treatment of Tuberculosis, American Thoracic Society, CDC, and Infectious Diseases Society of America. MMWR Morb Mortal Weekly Rep 2003;52(No. RR-11):1-88

Day(s) Performed

Monday through Friday

Report Available

5 to 7 days

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

87556-Mycobacterium tuberculosis, complex, molecular detection, PCR, Paraffin

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MTBT MTB complex PCR, FFPE 38379-4

 

Result ID Test Result Name Result LOINC Value
SRCTB MTB Complex PCR, FFPE, Source 31208-2
TBRR MTB Complex PCR, FFPE, Result 38379-4
Mayo Clinic Laboratories | Microbiology and Infectious Disease Catalog Additional Information:

mml-mycobacteria