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Test Code LAB7356 Mycobacterium tuberculosis PCR

Methodology

Methodology

The Xpert MTB/RIF Assay, performed on the GeneXpert Instrument Systems, is a qualitative, nested real-time polymerase chain reaction (PCR) diagnostic test for the detection of Mycobacterium tuberculosis complex DNA.

 

Testing Algorithm:

  1. PCR for Mycobacterium tuberculosis complex (MTBC) will be performed on respiratory related specimens (i.e. bronchial alveolar lavage, bronchial washing, induced sputum, sputum, tracheal aspirate, or plueral fluid) on positive acid-fast stain or when specifically ordered.
  2. Mycobacteriology (AFB) culture will also be performed on all specimens submitted for Mycobacterium tuberculosis PCR

 

Specimen Requirements

Acceptable Specimens:

 

Bronchial or tracheal: >5 mL in a leakproof, screw-capped, sterile container.

 

Sputum: >5 mL in a leakproof, screw-capped, sterile container.

 

Plueral fluid:  >5 mL in a leakproof, screw-capped, sterile container. 

 

Collection procedure:

 

Note: Specimen source is required.

 

Broncheal or Tracheal

  1. Aseptically collect >5 mL of fluid.
  2. Place in a leakproof, screw-capped, sterile container.
  3. Maintain sterility and transport promptly to laboratory.
  4. If transport is delayed, refrigerate specimen.

 

Pleural fluid

  1. Aseptically collect >5 mL of fluid.
  2. Place specimen in a leakproof, screw-capped, sterile container.
  3. Maintain sterility and transport promptly to laboratory.
  4. If transport is delayed, keep specimen at room temperature.

 

Sputum

  1. Aseptically collect early morning specimen in a leakproof, screw-capped, sterile container. It is optimal to collect a specimen each day for 3 consecutive days. (Note: Saliva is NOT acceptable)
  2. Instruct patient to brush his/her teeth and rinse mouth with water.
  3. Have patient remove any dentures.
  4. Instruct patient to take a deep breath, hold momentarily, then cough deeply and vigoroursly into leakproof, screw-capped, sterile container. Collect >5 mL of discharged material.
  5. Maintain sterility and transport promptly to laboratory.
  6. If transport is delayed, refrigerate specimen.

Day(s) Test Set Up

Monday through Sunday

Cutoff time for same day results: 1600

 

Turnaround Time:

STAT: Not available

Routine: 24 hours

Reference Values

Mycobacterium tuberculosis Complex Not Detected.

 

Literature Reference:

Della-Latta P., Mycobacteriology and Antimycobacterial Susceptibility Testing. In: Leber, Amy, ed. Clinical microbiology procedures handbook. 4th ed. Washington DC: American Society for Microbiology; 2016:7.6.

Specimen Transport Temperature

Ambient/Refrigerate OK

Additional Information

For BJH Laboratory Use Only

 

Minimum volume: 1.5 mL

 

Test performed in BJH Microbiology

Test Classification and CPT Codes

87556 - Infectious agent detection by nucleic acid (DNA or RNA): Mycobacterium tuberculosis, amplified probe technique

87116 - Culture, Mycobacterium

87206 - Smear fluorescent, acid-fast (if appropriate)