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DIRECT DETECTION FOR NUCLEIC ACID OF M. TUBERCULOSIS COMPLEX – XPERT MTB/RIF ASSAY

Synonym(s):

TB PCR, Xpert MTB/RIF Assay

Lab Section Category

Description

Indications

Specimen Required

​As for Mycobacterial Culture, except that blood and bone marrow specimens should be collected in sterile screw-capped containers or plain Vacutainer tubes (NOT in Myco-F-Lytic vials) and delivered to the lab immediately. If delay is unavoidable, collect in EDTA or citrated tubes, though amplification results may be less consistent.

Storage and Transport

​Collect in a dedicated container. Do not order non-CTBL tests using the same request form and on the same specimen. Specimens should reach CTBL within 24 hours of collection. If transport delay is unavoidable, store at 40C.

Method

​Xpert MTB/RIFAssay using Real-time Polymerase Chain Reaction

Test Results

M. tuberculosis complex DNA detected / Not detected / Indeterminate
Mutation in rpoB gene leading to Rifampicin resistance detected / Not detected

(Note : Test for Rifampicin resistance has not been validated in-house)

Reference Interval / Value

Turnaround Time

​1-2 working days

Day(s) Test Set up

​Monday through Friday

Remarks

​Reflex Testing: These tests only provide preliminary information for empirical TB management. A reflex AFB culture, including an AFB smear for respiratory samples if the volume is adequate, is also set up for each specimen. These additional tests are chargeable. Written instruction from the doctor is necessary if these are not to be performed.

Change History Notes

  • 29 Apr 2016 05:15 PM

    Add in Indeterminate for test result. Amend Turnaround time into 1-2 working days

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