Second Line LPA [SLLPA]

Second-line Line Probe Assay (SL-LPA) is a LPA to detect resistance to the second-line anti-TB drugs. This test is recommended for identifying TB patients with Multidrug-resistance (MDR) or rifampicin-resistance and those who can be placed on the shorter MDR-TB regimen.

The SL-LPA produces results in just 24-48 hours.

• It is performed using GenoType MTBDRsl Version 2.
• This is a DNA-based test that identifies genetic mutations in MDR-TB strains, making them resistant to fluoroquinolones and injectable second-line TB drugs.
• GenoType MTBDRsl Version 2 (Figure) identifies:
  • Quinolone-resistance determining region (QRDR) of gyrA (from codon 85 to 96) and of gyrB (from codon 536 to 541) genes for detection of resistance to fluoroquinolones
  • rrs (nucleic acid position 1401, 1402 and 1484), eis promoter region (from -37
    to -2 nucleotides upstream, low level kanamycin resistance) for detection of resistance to SLI drugs.
• Single mutation in gyrA confers low level fluoroquinolone resistance.
• Concurrent mutations in gyrA or both gyrA and gyrB confer high level fluoroquinolone resistance.

Figure: GenoType MTBDRsl Version 2 SL-LPA strip to determine Wild Type genes and mutations responsible for Resistance to Fluoroquinolones and Second-line Injectable Drugs; Source: GLI LPA Guidance Document.

Resources

• Guidelines for PMDT in India, 2021.​
• GLI LPA Guidance Document.

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