4.2 Algorithm 2 – LF-LAM testing to aid in the diagnosis of TB among PLHIV

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). LF-LAM results (test time <15 minutes) are likely to be available before mWRD results, and treatment decisions should be based on the LF-LAM result while awaiting the results of other diagnostic tests.

The currently available LF-LAMs have sufficient sensitivity and specificity to aid in the diagnosis of TB among individuals coinfected with HIV, but have suboptimal sensitivity and specificity in those who are HIV-negative. Hence, this algorithm emphasizes the use of the LF-LAM test as a diagnostic test in all PLHIV with signs and symptoms of TB, as well as in other specific scenarios (described below) for the diagnosis of TB among PLHIV (52). The ease of use of the LF-LAM test makes it suitable for implementation outside of the laboratory – for example, in clinics (especially in those that see critically ill PLHIV) – for rapid diagnosis of TB and treatment initiation in urgent cases of suspected TB among PLHIV. Algorithm 2a is used for PLHIV being evaluated for TB (pulmonary or extrapulmonary) in an inpatient setting. The updated WHO screening guidelines now recommend adult and adolescent inpatients with HIV in medical wards where the TB prevalence is more than 10% should be tested systematically for TB disease with an mWRD, as described in Algorithm 1 (9). This is in addition to the recommendations on the use of LF-LAM among inpatient PLHIV (49). Algorithm 2b is used for PLHIV being evaluated for TB (pulmonary or extrapulmonary) in an outpatient setting or clinic.

These algorithms are appropriate for both low and high MDR-TB or Hr-TB burden settings. The choice of which molecular test to use may be different in a low or high MDR-TB or Hr-TB burden setting, as discussed under Algorithm 1. For example, in a setting with a high burden of MDR-TB, it would be preferable to use an mWRD that detects MTBC and RIF resistance simultaneously (e.g. Xpert MTB/RIF), rather than an mWRD that uses a two-step process (e.g. Truenat MTB) to detect RIF resistance.

Fig. 4.3. Algorithm 2a: LF-LAM to aid in the diagnosis of TB among PLHIVᵃ in inpatient settings

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Fig. 4.4. Algorithm 2b: LF-LAM testing to aid in the diagnosis of TB among PLHIVᵃ in clinic and outpatient settings

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