Operational Handbooks

Algorithm 3 is a follow-on algorithm, the purpose of which is to detect resistance in individuals with RIF-susceptible TB who are at risk of having DR-TB and individuals with Hr-TB (Fig. 6.6). People at high risk for having DR-TB include those who have prior drug exposure; reside in settings where the probability of resistance to RIF, INH or FQs is high (≥5%), or belong to subgroups where the probability of such resistance is high; or have a history of contact with a person known to have DR-TB.

Algorithm 2a and 2b are used for further evaluation of people with MDR/RR-TB. In its most recent recommendations (7), WHO strongly encourages DST in people with MDR/RR-TB, although that should not delay treatment initiation. DST should be performed as soon as possible and even if results are not available at the start of the selected regimen (preferably BPaLM or BDLLfxC), the results should be used to adjust it. Two of the key medicines in these regimens are BDQ and FQ.

Algorithm 1 is the starting point for the diagnostic pathway, and in this context the recommended classes of WRDs include both molecular tests (LC-mNAAT, LC-aNAAT and MC-aNAAT) and a biomarker-based test (LF-LAM) (Fig. 6.2). Member States can choose the mWRD that best fits their circumstances, with the ultimate objective being to serve patient needs and ensure universal access to diagnostic and RIF-resistance testing. The mWRD classes provide different types of results:

Although the algorithms are presented separately, they are interlinked and cascade from one to another. This is illustrated in the overview in Fig. 6.1, which describes how the different algorithms cascade from the starting point of a person being evaluated for TB. If the person screens positive, or is presumed to have TB, samples are collected for diagnostic and RIF-resistance testing according to Algorithm 1.

Modifications to diagnostic algorithms must be put in place only after a formal evaluation, review and approval by officials within the ministry of health, NTP and NTRL. Often, nationally appointed thematic working groups are used to evaluate new technologies and develop implementation plans, which typically include revising current algorithms. These working groups comprise local ministry officials, implementing partners, civil society and professionals (laboratory and medical), who will decide the optimal use and placement of the new technology within the current network structure.

Effective and efficient TB diagnostic algorithms are key components of a diagnostic cascade that is designed to ensure that people with TB disease or TB infection are diagnosed accurately and rapidly, and promptly placed on appropriate therapy. In turn, that therapy should improve patient outcomes, reduce transmission and avoid development of drug resistance. This section presents a set of four model algorithms that incorporate the goals of the End TB Strategy and the most recent WHO recommendations for the diagnosis and treatment of TB, DR-TB and TB infection.

Step 10.1 – Monitor implementation of the diagnostic test

Step 9.1 – Develop terms of reference and position descriptions

Step 8.1 – Review and revise request for examination and reporting forms

Step 7.1 – Implement a comprehensive QA system

A comprehensive QMS is needed to ensure the accuracy, reliability and reproducibility of test results. Essential elements of a QA system include: