Reporting the Result of First-line Line Probe Assay [FL-LPA] in Special Cases

Reporting Drug-resistance in Special Cases

• When specimen tested contains hetero resistant strain:
  • Strips contain both wild type and mutant probes for three genes known for resistance to Rifampicin and Isoniazid
    • Bands to be interpreted as indicating resistance to a particular drug; should be reported as such
    • Example of hetero resistant strain: rpoB WT 8 and rpoB MUT 3 bands are present
• The tested specimen contains more than one Mycobacterium tuberculosis complex strain (due to mixed culture/ non-tuberculous mycobacterium or contamination):
  • If any strains harbor mutation, one mutation probe, as well as the corresponding wild type probe, may stain positive; ascertain the presence of TUB band
  • Repeat test or phenotypic testing to confirm resistance
• Presence of non-tuberculous mycobacterium:
  • TUB band missing; not be reported as M. tuberculosis
  • TUB band absent but random banding patterns visible, eg: bands at rpoB WT 1, 4, 5 or 8; not be reported as M. tuberculosis

Resources

• GenoType MTBDR plus Ver 2.0 Kit, Instructions for Use.
• Line Probe Assays for Drug-resistant Tuberculosis Detection, GLI.
• Molecular Detection of Drug-resistant Tuberculosis by Line Probe Assay.

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