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HelpTest 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
Detecting M tuberculosis complex
This test 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 or an interferon gamma release assay.
Method Name
Real-Time Polymerase Chain Reaction (PCR)
Reporting Name
MTB complex PCR, FFPESpecimen Type
Tissue, ParaffinAdditional Testing Requirements
When non-fixed specimen is available, a mycobacterial culture on that specimen must always be performed in addition to this test. If your facility is unable to perform mycobacterial culture, order CTB / Mycobacteria and Nocardia Culture, Varies concurrently with this test.
Necessary Information
Specimen source is required.
Specimen Required
The high sensitivity of amplification by polymerase chain reaction 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 FFPE 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 more than a million deaths and is responsible for millions of 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 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 polymerase chain reaction (PCR) assay detects M tuberculosis complex DNA directly from specimens without waiting for growth in culture and, therefore, the results are available rapidly after receipt in the laboratory. A mycobacterial culture must always be performed in addition to the PCR assay. The PCR assay is rapid, but culture has increased sensitivity over the PCR assay. 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 mutations 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, Mycobacterium bovis, Mycobacterium bovis bacillus Calmette-Guerin (BCG), Mycobacterium africanum, Mycobacterium canettii, and Mycobacterium microti. The other species within the M tuberculosis complex (eg, Mycobacterium caprae, Mycobacterium pinnipedii, and Mycobacterium 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. 2nd ed. Lippincott Williams and Wilkins; 2013
2. American Thoracic Society; Centers for Disease Control and Prevention; Infectious Diseases Society of America. Treatment of tuberculosis. MMWR Recomm Rep. 2003 Jun 20;52(RR-11):1-77. Erratum in: MMWR Recomm Rep. 2005 Jan 7;53(51):1203
3. Ortiz-Brizuela E, Menzies D, Behr Mad: Testing and treating Mycobacterium tuberculosis infection. Med Clin North Am. 2022 Nov;106(6):929-947. Doi: 10.1016/j.mcna.2022.08.001
Day(s) Performed
Monday through Sunday
Report Available
5 to 7 daysTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
87556
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 |
mml-mycobacteria