Test Catalog

Test Id : MTBRP

Mycobacterium tuberculosis Complex, Molecular Detection, PCR, Varies

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

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 (TST/PPD) or an interferon gamma release assay (IGRA).

Reflex Tests
Lists tests that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial tests.

Test Id Reporting Name Available Separately Always Performed
TBT Concentration, Mycobacteria No, ( Bill Only) No

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

When this test is ordered, the reflex test may be performed and charged.

 

See Meningitis/Encephalitis Panel Algorithm in Special Instructions.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Real-Time Polymerase Chain Reaction (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 Complex PCR

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

Acid-Fast Bacilli (AFB)

AFB (Acid-Fast Bacilli)

Bacillus, Acid-Fast

MTB (Mycobacterium tuberculosis)

Mycobacterium tuberculosis (MTB)

TB (Tuberculosis)

Tubercle Bacilli: Mycobacterium tuberculosis

Tuberculosis (TB)

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

When this test is ordered, the reflex test may be performed and charged.

 

See Meningitis/Encephalitis Panel Algorithm in Special Instructions.

Specimen Type
Describes the specimen type validated for testing

Varies

Additional Testing Requirements

This test should always be performed in conjunction with mycobacterial culture.

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
SRC62 MTB Complex PCR, 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.

 

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

 

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 fluid is 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: 5-10 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: 5-10 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.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

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

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

Body fluid: 0.5 mL

Respiratory specimen-nondigested: 0.5 mL

Fresh tissue or bone: 5 mm

NALC-NaOH-digested specimen: 1 mL

Gastric washing: 1 mL

Stool: 5 g

Urine: 0.5 mL

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

Other Blood Specimen in anaerobe vial or viral transport medium (including but not limited to M4, M5, BD viral transport media, thioglycolate broth) Swabs Tissues in formalin fluid
 

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
Varies Refrigerated (preferred) 7 days
Frozen 7 days

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

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 (TST/PPD) or an interferon gamma release assay (IGRA).

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

When this test is ordered, the reflex test may be performed and charged.

 

See Meningitis/Encephalitis Panel Algorithm in Special Instructions.

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

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. 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.

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.

Not applicable

Interpretation
Provides information to assist in interpretation of the test results

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. 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. 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.

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

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.

Supportive Data

The analytical specificity of the assay was determined using Basic Local Alignment Search Tool (BLAST) analysis of the National Center for Biotechnology Information (NCBI) GenBank database and no sequences were detected that would interfere with the LightCycler PCR assay. Further, the assay was tested using a panel of 104 respiratory pathogens (bacteria and viruses) that were extracted and subjected to the LightCycler PCR assay. As predicted, only Mycobacterium tuberculosis complex was detected from this panel. In addition, nearly 100 species of nontuberculous mycobacteria were evaluated using this PCR assay and there was no cross-reactivity detected. The analytical sensitivity of the assay was determined to be 10 target copies/microliter using a dilution series of M tuberculosis spiked into respiratory specimens in triplicate.

 

The sensitivity and specificity of the assay for detection of M tuberculosis complex verses culture was found to be 100% and 100% respectively for 26 M tuberculosis-positive cultures and 266 M tuberculosis-negative cultures. The PCR inhibition rate of the assay was determined to be 0% by spiking 100 negative extracted respiratory specimens with M tuberculosis at 100 targets/microliter. The PCR assay was able to detect 100% of specimens spiked at the limit of detection for bronchoalveolar lavage (BAL) fluid, muscle/skin tissue, organ tissues, bone, cerebrospinal fluid (CSF), and urine. One of 30 (3%) of spiked respiratory tissues was inhibited and 3 of 30 (10%) of spiked sterile body fluids other than CSF were inhibited. Not surprising increased inhibition was seen in stool (24 of 30 spiked specimens were positive) and formalin-fixed, paraffin-embedded tissue (19 of 30 spiked specimens were positive).

 

Method comparison of the LightCycler PCR assay versus mycobacterial culture was done using 192 respiratory specimens. The results are shown in Table 1.

 

Table 1. Results for the LightCycler PCR assay versus mycobacterial culture for 192 respiratory specimens.

 

 

Culture positive for Mycobacterium tuberculosis complex

 

+

-

Sensitivity

Specificity

LightCycler PCR

+

33

1

87%

99%

-

5

153

 

Table 2 provides a comparison of the LightCycler PCR assay versus the GEN-PROBE Mycobacterium tuberculosis Direct (MTD) assay, performed using 542 respiratory specimens (226 BAL fluids, bronchial washings and lung washings plus 316 sputa, induced sputa, and tracheal secretions). The kappa coefficient of 0.96 indicates excellent agreement between the 2 methods.

 

Table 2. Clinical sensitivity of the LightCycler PCR versus MTD for respiratory specimens.

 

 

Assay

MTD

 

+

-

Agreement (%)

kappa coefficient

LightCycler PCR

+

49

1

538/542 (99.3%)

0.96

-

3

489

 

Two melt peaks can be produced during this assay. A melt peak at a temperature of 64.0 degrees C + or - 2.5 degrees C can correspond to either isoniazid-susceptible or isonazid-resistant M tuberculosis and, therefore, no indication of isoniazid susceptibility is provided for these isolates. However, an isolate with melt peak occurring at a temperature of 58.0 degrees C + or - 2.5 degrees C correlated with isoniazid resistance determined using a broth reference method in 100% (26/26) of isolates tested. Isolates with a peak at a temperature of 58.0 degrees C + or - 2.5 degrees C are reported as "Positive, probable isoniazid resistance detected." The PCR result is available 7 to 14 days prior to the broth method and, therefore, may be helpful in selecting appropriate antibiotic therapy for these patients. Confirmation of isonaizid resistance must be done using a phenotypic method if the isolate grows in culture.

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

1. Iseman MD: A clinician’s guide to tuberculosis. Philadelphia, PA. Lippincott Williams and Wilkins, 2000

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

Special Instructions
Library of PDFs including pertinent information and forms related to the test

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

Following specimen digestion and decontamination using N-acetyl cysteine and sodium hydroxide, genomic DNA is extracted using the MagNA Pure Compact (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 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.(Unpublished Mayo method)

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.

1 to 3 days

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 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
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-Mycobacterium tuberculosis, complex, molecular detection, PCR

87015-Mycobacteria culture, concentration (if appropriate)

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
MTBRP M tuberculosis Complex PCR 38379-4
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.
SRC62 MTB Complex PCR, Specimen Source 31208-2
56044 MTB Complex PCR, Result 38379-4

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