Mycobacterium tuberculosis (TB) PCR, Sputum

Overview
Department	Microbiology - Molecular
Test Code	TB
Synonyms	Mycobacterium tuberculosis, TB MTB ZN AFB
Availability	Monday to Friday Not routinely available out of hours
Turnaround Time	24 - 72 hours
Stability - Add test
Specimen Requirements
Specimen	Sputum
Preferred	Only after consultation with the Clinical Microbiologist and/or Consultant Physician
Acceptable	2 mL Sputum sample - induced or expectorated
Unacceptable	Leaking samples Unlabelled samples
Specimen Transportation	ASAP to Laboratory
Paediatric Requirements	2 mL Sputum sample - induced or expectorated
Aliquot Requirements
Sample
Preferred Volume
Minimum Volume
Aliquot Transportation	If there is a delay in getting sample to the laboratory, please store sample chilled (2 - 8 degrees Celsius)
Clinical Information
Reference Intervals	Results reported as MTB Complex DNA Result: DETECTED or NOT Detected. If MTB Complex DNA DETECTED - Rifampicin resistance will be reported as DETECTED or NOT Detected. These results and susceptibilities will be confirmed upon TB Culture testing at reference laboratory.
Test Method	Semi-quantitative, nested real-time PCR for the detection of Mycobacterium tuberculosis (MTB) complex DNA.
Advanced Notice	Not required
Patient Preparation	Not Required
Comments
Sputum TB PCR requests can only be approved after consultation with Clinical Microbiologist and/or Consultant Physician. The detection of the M. tuberculosis complex DNA and the detection of Rifampicin-resistance associated mutations of the rpoB gene from direct sputum. All sputum samples requested for TB PCR will be forwarded to a reference laboratory for TB Culture (Taranaki Pathology Services testinfo-viewer (labapps.nz) ) Please note: Culture remains the gold standard for the detection of M. tuberculosis. TB PCR requests will be performed on sputum samples from patients suspected of having TB and/or where there are public health or infection control concerns. All requests should include relevant clinical details. Specimens that fail for technical reasons will be forwarded to the reference laboratory for routine TB Culture. TB PCR may be re-tested dependant on volume of sample received, or if a re-collect is possible, meaning results will be delayed. If sample volume does not meet requirements the requestor will be contacted, and the sample will be referred for routine TB Culture.

Owner	Melanie Williams (Williams1)
Last reviewed	12.09.2025
Next review	12.09.2026 (Overdue)