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Test ID: MTBXP Mycobacterium tuberculosis complex, Molecular Detection, PCR, Sputum


Shipping Instructions


Specimen must arrive within 7 days of collection; specimen >7 days will be rejected.



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.

 

Specimen Type: Sputum (undigested)

Container/Tube: Sterile container

Specimen Volume:  3 mL

Specimen Stability Information: Refrigerated (preferred) 7 days/Ambient 72 hours

Additional Information:

1. If a single specimen is being shared between mycobacteria culture, acid-fast smear, and/or M tuberculosis PCR, a minimum volume of 3 mL for respiratory specimen is required. Specimen volumes less than indicated may decrease sensitivity of testing.

2. If insufficient volume is submitted, test or tests will be canceled.

 

Specimen Type: N-acetyl-l-cysteine/sodium hydroxide (NALC/NaOH)-digested sputum

Container/Tube: Sterile container

Specimen Volume: 3 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.

Specimen Stability Information: Refrigerated 7 days

Additional Information:

1. If a single specimen is being shared between mycobacteria culture, acid-fast smear, and/or M tuberculosis PCR, a minimum volume of 3 mL for respiratory specimen is required. Specimen volumes less than indicated may decrease sensitivity of testing.

2. If insufficient volume is submitted, test or tests will be canceled.


Useful For

Rapid detection of Mycobacterium tuberculosis DNA from respiratory specimens for the diagnosis of pulmonary tuberculosis

 

Presumptive detection of rifampin resistance based on the presence of resistance-associated mutations

Method Name

Real-Time Polymerase Chain Reaction (RT-PCR)

Reporting Name

M. tuberculosis/RIF PCR GeneXpert

Specimen Type

Sputum

Specimen Minimum Volume

1.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Sputum Varies

Clinical Information

Mycobacterium tuberculosis is a highly transmissible bacterial pathogen and is the causative agent of tuberculosis, a disease causing significant worldwide morbidity and mortality. Each year, M tuberculosis accounts for nearly 1.3 million deaths and is responsible for 10 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 of the antibiotics currently used if not treated appropriately. 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 6 weeks of incubation may be required in some instances. This qualitative molecular assay utilizes PCR-based nucleic acid amplification for the direct detection of M tuberculosis DNA within respiratory specimens without relying on culture growth, leading to more rapid diagnoses and appropriate patient care. This assay also detects the presence of mutations in the rpoB gene that have been documented to confer more than 95% of cases of rifampin resistance.

Reference Values

Negative

Interpretation

A positive result indicates the presence of Mycobacterium tuberculosis complex DNA.

 

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

 

Presumptive rifampin (RIF) resistance mediated through mutations within the resistance determining region of the rpoB gene will be reported when detected.

 

One to 2 negative PCR results in conjunction with 1 to 2 negative acid-fast smears may provide evidence supporting the removal of a patient from airborne isolation. Consult your local Infection Prevention and Control for guidance.

Clinical Reference

1. World Health Organization. Global Tuberculosis Report, 20th edition. Geneva, Switzerland. 2015 Available at www.who.int/tb/publications/global_report/gtbr15_main_text.pdf

2. Centers for Disease Control and Prevention. Availability of an assay for detecting Mycobacterium tuberculosis, including rifampin-resistant strains, and considerations for its use - United States, 2013. MMWR Morb Mortali wkly rep 2013;62:821-827

3. Boehme CC, Nabeta P, Hillemann D, et al: Rapid Molecular Detection of Tuberculosis and Rifampin Resistance. N Engl J Med 2010;9:1005-1015

4. Food and Drug Administration. New data shows test can help physicians remove patients with suspected TB from isolation earlier. Press Release. 2015 Feb 12. Available at www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm434226.htm

Day(s) Performed

Monday through Sunday

Report Available

Same day/1 day

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

87556, 87798

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MTBXP M. tuberculosis/RIF PCR GeneXpert 89371-9

 

Result ID Test Result Name Result LOINC Value
SRCRF Specimen Source 31208-2
MTBXR MTB Complex Result 88874-3
RIFAR MTB Rifampin Resistance Result 89372-7
Mayo Clinic Laboratories | Microbiology and Infectious Disease Catalog Additional Information:

mml-mycobacteria