Test Id : MTBRP

When this test is ordered, the reflex test may be performed at an additional charge.

For more information see Meningitis/Encephalitis Panel Algorithm.

This test must always be performed in conjunction with mycobacterial culture. If your facility is unable to perform mycobacterial culture, order CTB / Mycobacteria and Nocardia Culture, Varies concurrently with this test.

Specimen must arrive within 7 days of collection; if greater than 7 days of collection, the specimen will be rejected.

Specimen source is required.

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

If a single specimen is being shared between mycobacteria culture, acid-fast smear, and/or M tuberculosis PCR, a minimum volume of 2 mL for body fluid, 3 mL for respiratory specimen, or a pea-sized piece of tissue should be obtained. Specimen volumes less than indicated may decrease sensitivity of testing. If insufficient volume is submitted, test or tests will be canceled.

Preferred Specimens: Body fluid, cerebrospinal fluid (CSF), ocular fluid, respiratory (eg, bronchoalveolar lavage [BAL], bronchial washing, sputum), feces, fresh tissue, bone, bone marrow, or urine

Submit a raw clinical sample (not a culture isolate) for testing.

Acceptable Specimens: If no fresh specimen is available, digested respiratory specimens treated with N-acetyl-L-cysteine/sodium hydroxide (NALC/NaOH) are acceptable (eg, BAL, bronchial washing, respiratory fluid, sputum, or tracheal secretion), as are NALC/NaOH-treated gastric washings.

Submit only 1 of the following specimens:

Specimen Type: Body fluid

Sources: Body, bone marrow aspirate, ocular, or CSF

Container/Tube: Sterile container

Specimen Volume: 1 mL

Additional Information: Only fresh, non-NALC/NaOH-digested body fluids are acceptable.

Specimen Type: Gastric washing

Container/Tube: Sterile container

Specimen Volume: 2 mL

Collection Instructions: Neutralize specimen within 4 hours of collection with 20 mg of sodium carbonate per 2 mL of gastric washing.

Specimen Type: Respiratory

Sources: BAL, bronchial washing, or sputum

Container/Tube: Sterile container

Specimen Volume: 1 mL if only PCR ordered or 3 mL if PCR ordered with smear and culture

Specimen Type: Feces

Container/Tube: Sterile container

Specimen Volume: 5 to 10 g

Additional Information: Only fresh, non-NALC/NaOH-digested fecal specimens are acceptable.

Specimen Type: Tissue

Sources: Fresh tissue, bone, or bone marrow biopsy

Container/Tube: Sterile container

Specimen Volume: 5 to 10 mm

Collection Instructions: Keep moist with sterile water or sterile saline

Additional Information: Only fresh, non-NALC/NaOH-digested tissue is acceptable.

Specimen Type: Urine

Container/Tube: Sterile container

Specimen Volume: 1 mL

Collection Instructions: Collect a random urine specimen.

Acceptable

Specimen Type: NALC/NaOH-digested respiratory specimens

Sources: Lavage fluid, bronchial washing, gastric washing, respiratory fluid, sputum, or tracheal secretion

Container/Tube: Sterile container

Specimen Volume: 2 mL

Collection Instructions:

1. Submit digested specimen treated with NALC/NaOH.

2. Clearly indicate on container and order form that specimen is a digested specimen.

• Meningitis/Encephalitis Panel Algorithm

If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.

Body fluid, nondigested respiratory specimen, urine: 0.5 mL; Fresh tissue or bone: 5 mm; NALC-NaOH-digested specimen, gastric washing: 1 mL; Stool: 5 g

Rapid detection of Mycobacterium tuberculosis complex DNA (preferred method)

Detection of M tuberculosis, when used in conjunction with mycobacterial culture

This test should not be used to determine bacteriologic cure or to monitor response to therapy.

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.

When this test is ordered, the reflex test may be performed at an additional charge.

For more information see Meningitis/Encephalitis Panel Algorithm.

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 the 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.

Not applicable

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, Mycobacterium africanum, Mycobacterium canettii, and Mycobacterium microti. 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. This assay method does not distinguish between the species of the M tuberculosis complex. If an isolate of M tuberculosis complex is already available, species identification can be performed; order TBSP / Mycobacterium tuberculosis Complex Species Identification, PCR, Varies.

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.

A mycobacterial culture must always be performed in addition to the polymerase chain reaction (PCR) test. If your facility is unable to perform mycobacterial culture, the Mycobacteria Culture test (CTB / Mycobacteria and Nocardia Culture, Varies) should be ordered. The overall sensitivity of the PCR from acid-fast smear positive specimens is approximately 96% compared to mycobacterial culture but sensitivity of the PCR from a smear negative specimen is lower and a negative result does not rule out M. tuberculosis complex.

This rapid PCR assay detects Mycobacterium tuberculosis complex nucleic acid and, therefore, does not distinguish between viable, disease-related organisms and nucleic acid persisting from prior infection. Test results should be correlated with patient symptoms and clinical presentation before a definitive diagnosis is made.

A negative result does not rule out the presence of M tuberculosis complex or active disease because the organism may be present at levels below the limit of detection for this assay.

This test has not been studied for use with specimens from patients being treated with antituberculous agents and, therefore, should not be used to determine bacteriologic cure or to monitor response to therapy. It is not known how long the PCR assay can remain positive following treatment for M tuberculosis.

The sensitivity of this test with stool specimens is 80% and testing of additional stool specimens should be considered if the result from the first specimen is negative.

1. Lewinsohn DM, Leonard MK, LoBue PA, et al: Official American Thoracic Society/Infectious Diseases Society of America/Centers for Disease Control and Prevention Clinical Practice Guidelines: Diagnosis of Tuberculosis in Adults and Children. Clin Infect Dis. 2017 Jan 15;64(2):e1-e33. doi: 10.1093/cid/ciw694

2. Nahid P, Dorman SE, Alipanah N, et al: Official American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America Clinical Practice Guidelines: Treatment of Drug-Susceptible Tuberculosis. Clin Infect Dis. 2016 Oct 1;63(7):e147-e195. doi: 10.1093/cid/ciw376

3. Ortiz-Brizuela E, Menzies D, Behr MA: Testing and treating Mycobacterium tuberculosis infection. Med Clin North Am. 2022 Nov;106(6):929-947. doi: 10.1016/j.mcna.2022.08.001

Following specimen digestion and decontamination using N-acetyl cysteine and sodium hydroxide, genomic DNA is extracted using the MagNA Pure (Roche Applied Sciences) extraction platform. The purified genomic DNA is placed on the LightCycler instrument, which amplifies and monitors, by fluorescence, the development of target nucleotide sequences after each polymerase chain reaction (PCR) cycle. A specific target sequence from a portion of the katG gene from Mycobacterium tuberculosis complex is amplified and the resulting segment is detected by melt-curve analysis using sequence-specific fluorescence resonance energy transfer hybridization probes. The LightCycler PCR assay is a closed PCR system that greatly reduces the potential for false-positive results due to specimen cross-contamination as compared with traditional open-system PCR or other amplification methods like transcription-mediated amplification.(Buckwalter SP, Connelly BJ, Louison LK, et al: Description, validation, and review of a decade of experience with a laboratory-developed PCR test for detection of Mycobacterium tuberculosis complex in pulmonary and extrapulmonary specimens. J Clin Tuberc Other Mycobact Dis. 2022 Nov 12;29:100340. doi: 10.1016/j.jctube.2022.100340)

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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.

87556-Mycobacterium tuberculosis, complex, molecular detection, PCR

87015-Mycobacteria culture, concentration (if appropriate)