Test Catalog

Test Id : MTBXP

Mycobacterium tuberculosis complex, Molecular Detection, PCR, Sputum

Useful For
Suggests clinical disorders or settings where the test may be helpful

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
A short description of the method used to perform the test

Real-Time Polymerase Chain Reaction (RT-PCR)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

M. tuberculosis/RIF PCR GeneXpert

Aliases
Lists additional common names for a test, as an aid in searching

Latent tuberculosis (LTBI)

Mycobacterium tuberculosis (MTB)

Tubercule bacilli: Mycobacterium tuberculosis

Tuberculosis (TB)

Rifampin

GeneXpert

MTB PCR

Specimen Type
Describes the specimen type validated for testing

Sputum

Shipping Instructions

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

Necessary Information

Specimen source is required.

ORDER QUESTIONS AND ANSWERS

Question ID Description Answers
SRCRF Specimen Source

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

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.

Forms

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

1.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Sputum Varies

Useful For
Suggests clinical disorders or settings where the test may be helpful

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

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative

Interpretation
Provides information to assist in interpretation of the test results

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.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test should always be performed in conjunction with mycobacterial culture, which is required for epidemiological strain typing and definitive drug susceptibility testing.

 

Per current CDC recommendations, rifampin resistance results should be considered as preliminary pending confirmation with gene sequencing or growth-based phenotypic drug susceptibility testing.

 

This PCR-based molecular assay detects Mycobacterium tuberculosis 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 infection with M tuberculosis or active disease because the organism may be present at levels below the limit of detection for this assay.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

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

Method Description
Describes how the test is performed and provides a method-specific reference

The Cepheid Xpert MTB/RIF assay utilizes sputum or decontaminated and pelleted sputum sediment. Specimens are inoculated directly into single disposable test cartridge, which contains both DNA extraction and target amplification material. The assay amplifies a 192-bp segment of the rpoB gene for Mycobacterium tuberculosis complex identification as well as rifampin resistance profiling. The Cepheid Xpert MTB/RIF 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 methods.(Package insert: Xpert MTB/RIF. Cepheid. Sunnyvale,CA. GXMTB/RIF-US-10, rev D, 03/2016)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Sunday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

Same day/1 day

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

7 days

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

87556, 87798

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
MTBXP M. tuberculosis/RIF PCR GeneXpert 89371-9
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
MTBXR MTB Complex Result 88874-3
RIFAR MTB Rifampin Resistance Result 89372-7
SRCRF Specimen Source 31208-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports