Mycobacterium and TB PCR

Microbiology

Notes

 

  • This is a rapid molecular test for the detection of M. tuberculosis complex and rifampicin resistance
  • Can be performed on a range of samples, both pulmonary and non-pulmonary
  • It is generally only performed after discussion with the Consultant Microbiologist
  • A negative result does not exclude the clinical possibility of TB infection, or infection with other Mycobacteria

Sample requirements

  • The ideal specimens are AAFB smear-positive pulmonary samples
  • In general fluid samples such as CSF, pleural fluid and ascites have much lower sensitivities; the minimum amount of CSF (not supernatant) that will be examined is 0.5ml. However submitting the largest possible volume of CSF and other fluids will increase the sensitivity.
  • This test can also be used to confirm positive cultures and to detect the presence of the rifampicin resistance gene
  • Paraffin waxed blocks can be examined but sensitivity is lower than that for fresh tissue. For paraffin wax blocks, the whole wax block must be sent together with a diagram/slide indicating the area where any AFB/granuloma were seen. The reference laboratory will return the block on completion of the test.

Required information

  • Relevant clinical details
  • Please provide details of any recent anti-tuberculosis treatment
  • Please provide details of recent BCG vaccination

Storage/transport

Transport to the laboratory immediately. Refrigerate samples if transport is delayed.

Turnaround time

Sent to a National Reference Centre

Up to 3 working days


Page last reviewed: 13/09/2017