In which settings is Xpert® MTB/RIF and LED microscopy screening for Tuberculosis for people living with HIV cost-effective?

Screening for tuberculosis among adults newly diagnosed with HIV in sub-Saharan Africa: a cost-effectiveness analysis.

Zwerling AA, Sahu M, Ngwira LG, Khundi M, Harawa T, Corbett EL, Chaisson RE, Dowdy DW. J Acquir Immune Defic Syndr. 2015 Sep 1;70(1):83-90. doi: 10.1097/QAI.0000000000000712.

Objective: New tools, including light-emitting diode (LED) fluorescence microscopy and the molecular assay Xpert® MTB/RIF, offer increased sensitivity for tuberculosis (TB) in persons with HIV but come with higher costs. Using operational data from rural Malawi, we explored the potential cost-effectiveness of on-demand screening for TB in low-income countries of sub-Saharan Africa.

Design and methods: Costs were empirically collected in 4 clinics and in 1 hospital using a microcosting approach, through direct interview and observation from the national TB program perspective. Using decision analysis, newly diagnosed persons with HIV were modeled as being screened by 1 of the 3 strategies: Xpert®, LED, or standard of care (ie, at the discretion of the treating physician).

Results: Cost-effectiveness of TB screening among persons newly diagnosed with HIV was largely determined by 2 factors: prevalence of active TB among patients newly diagnosed with HIV and volume of testing. In facilities screening at least 50 people with a 6.5% prevalence of TB, or at least 500 people with a 2.5% TB prevalence, Xpert® is likely to be cost-effective. At lower prevalence-including that observed in Malawi-LED microscopy may be the preferred strategy, whereas in settings of lower TB prevalence or small numbers of eligible patients, no screening may be reasonable (such that resources can be deployed elsewhere).

Conclusions: TB screening at the point of HIV diagnosis may be cost-effective in low-income countries of sub-Saharan Africa, but only if a relatively large population with high prevalence of TB can be identified for screening.

Abstract access  [1]

Editor’s notes: This study provides guidance on when screening people newly diagnosed with HIV for tuberculosis (TB) using Xpert® MTB/RIF or LED microscopy is likely to be cost-effective. Previous studies suggest that both TB screening technologies may be cost-effective, but that cost-effectiveness will depend on how tests are implemented. In highly resource constrained settings, the affordability of TB screening, particularly using Xpert® MTB/RIF, remains a concern. It therefore may not be feasible to place screening equipment at all locations, and more guidance is required on the types of setting where these investments may have the most benefit.

The study finds that two factors are particularly important in the choice of TB screening at any specific site. First, the authors find that test volumes are critical to cost-effectiveness. This finding supports earlier studies from South Africa prior to Xpert® MTB/RIF roll-out – that suggest that ‘economies of scale’ drive the unit costs per test. The authors of this study add to this previous evidence by providing a detailed example from a low income setting. Second, on the effect side, TB prevalence is found to be a key driver of cost-effectiveness.

The authors provide an illustration of a simple approach and model that can be used by countries to select the different TB screening tests required. It should be noted however, that the authors are not able to fully consider some factors that may have an important impact on the cost-effectiveness of TB screening, due to data scarcity. For example, the extent and speed to which people are appropriately treated for TB under each option (including the standard of care). This has been shown to be an important consideration in other studies investigating the cost-effectiveness of Xpert® MTB/RIF. It should also be noted that the study determines cost-effectiveness using an approach that may not fully reflect financial constraints. Therefore additional analyses, using local data, are still required before applying the study’s results in different settings.  

Africa [8]
Malawi [9]
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