Sign in →

Test Code LAB7356 Mycobacterium tuberculosis PCR from Direct Specimen

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 and rifampin resistance.

 

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. Gastric Aspirate specimens with a positive acid-fast stain will be submitted to a reference laboratory for reflex PCR test at an additional charge.
  2. Mycobacteriology (AFB) Respiratory Culture LAB10408 will also be performed on all specimens submitted for Mycobacterium tuberculosis PCR

Specimen Requirements

Acceptable Specimens:

 

Bronchoalveolar lavage (BAL), bronchial washing, tracheal: >5 mL in leakproof screw-capped, sterile container

 

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

 

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

 

Collection procedure:

 

 

Bronchial 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, refrigerate specimen.

 

Sputum

  1. Aseptically collect early morning specimen avoiding oral contamination in a leakproof , screw-capped, sterile container. It is optimal to collect a specimen each day for 3 consecutive days. (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: 1200

 

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 AL, Burnham C-AD, eds. Clinical Microbiology Procedures Handbook. 5th ed. Washington, DC: American Society for Microbiology; 2023.

Test Classification and CPT Codes

87564 - Nucleic acid amplification testing (NAAT) to detect Mycobacterium tuberculosis complex and rifampin resistance.

Specimen Transport Temperature

Ambient/Refrigerate OK

Additional Information

For BJH Laboratory Use Only

 

Minimum volume: 1.5 mL

 

Test performed in BJH Microbiology

Related Tests