Mycobacterium Tuberculosis PCR - Provincial
Discipline
Overview
Description
Mycobacterium tuberculosis most commonly causes pulmonary tuberculosis (TB), but can virtually infect any body tissue. The Xpert MTB/RIF assay is a nucleic acid amplification test (NAAT) that was developed and validated for use on respiratory samples; other specimens (e.g. CSF) can be tested upon microbiologist approval. TB NAAT testing does not distinguish between live and nonviable organisms. Although this assay includes a marker for rifampin resistance, TB culture is required for TB susceptibility testing.
Ordering recommendations
Patients with suspected pulmonary TB should have TB PCR ordered in addition to TB culture. This test is added in Saskatoon and Regina when respiratory specimen TB culture is requested from patients in hospital or ER; typically performed on the first submitted sample. Sputum TB NAAT will be run on outpatient specimens on request. Repeat NAAT testing or NAAT testing of non-respiratory specimens requires approval by a microbiologist.
Alias
- TB PCR
- GeneXpert TB
Specimen Information
Specimen types accepted
- Respiratory specimens, Sputum, PAL, Bronchial wash
- Other specimens types require Microbiologist On Call (MOC) approval
Specimen collection container
- Same as TB culture
Collection procedure
- Collect specimen in sterile container, transport to lab as soon as possible.
Required volume
- Same as TB culture
Performance
Maximum laboratory time
Results reporting
- Positive, negative, or indeterminate; Rifampin resistance marker reported for PCR positive specimens
Specimen retention time
- Regardless of PCR results all specimens are forwarded to the RRPL for culture and sensitivity
Other information
- This test may also be offered by peripheral laboratories with GeneXpert instruments.
- Only one specimen is allowed for GeneXpert testing within 3-month period. Repeats within 3 months of first testing are cancelled and may need to be approved by MOC for processing.
Last Updated: June 4, 2024