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Culture-based DST methods for certain anti-tuberculosis (anti-TB) medicines are reliable and reproducible, but these methods are time consuming, and require specific laboratory infrastructure, skilled staff and adherence to quality control.
Algorithm 3 is used for further evaluation of people with RR-TB or MDR-TB. In its most recent recommendations (9), WHO stresses the importance of DST before starting the preferred all-oral BDQ-containing MDR-TB regimen, especially for medicines for which mWRDs are available. Two of the key medicines in these regimens are BDQ and FQ. Currently, the only WHO-recommended molecular test to detect mutations associated with BDQ resistance is a targeted NGS test (Deeplex® Myc-TB from GenoScreen).
Algorithm 2 is the preferred algorithm for testing to support the diagnosis of TB in PLHIV. It is appropriate for use in settings with a high burden of HIV and for use with individual PLHIV who meet the testing criteria, regardless of the overall HIV burden. The algorithm emphasizes the use of LF-LAM to quickly identify people needing TB treatment; it also emphasizes that all individuals with signs and symptoms of TB should receive a rapid mWRD (Algorithm 1).
Tests
The mWRDs appropriate for this algorithm include the Xpert MTB/RIF, Xpert MTB/RIF Ultra, Truenat MTB, Truenat MTB Plus and TB-LAMP tests and moderate complexity automated NAATs.
Algorithm 1 is the preferred algorithm for testing to support the diagnosis of TB in individuals being evaluated for pulmonary and extrapulmonary TB, and to achieve universal DST. In this algorithm, mWRDs are used as the initial diagnostic test to detect TB, RIF resistance (except if TB-LAMP is used) and – in the case of using moderate complexity automated NAATs – INH resistance (i.e. this algorithm meets the goals of the End TB Strategy for the use of mWRDs and universal DST). If TB-LAMP is used, follow-on testing for RIF resistance is needed.
AMK
amikacin
BDQ
bedaquiline
BPaL
bedaquiline (B), pretomanid (Pa) and linezolid (L)
BPaLM
bedaquiline (B), pretomanid (Pa), linezolid (L) and moxifloxacin (M)
AFB
acid-fast bacilli
AHD
advanced HIV disease
AIDS
acquired immunodeficiency syndrome
ART
antiretroviral therapy
CC
The target audience for this guide includes ministry of health (MoH) officials, donors, implementing partners, programme managers, laboratory managers, clinicians and other key stakeholders engaged in TB laboratory strengthening or programme support.
This guide was developed to provide practical guidance for the implementation of WHO policies on recommended TB diagnostic tests and algorithms. The guide: