4.2.7
Line Probe Assay
National TB Management Guidelines, 2018 Edition. Chapter 4, Approach to TB diagnosis.
Clinical description
LPA is a rapid and accurate test to identify INH and RR strains of MTB. It can be performed either directly from smear-positive sputum samples or from culture isolates.
- If a patient with TB is smear-positive, the sputum contains enough bacilli to perform
an LPA directly on the sputum and DR-TB can be confirmed within two days.
- If the sputum is smear-negative, growth of bacilli should be demonstrated on culture
first (preferably on liquid medium) and then, LPA can be performed on the isolates to check for sensitivity for INH and rifampicin.
- LPA can also be performed to screen for resistance to other second-line TB drugs,
although these results would need careful interpretation.
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