Cost utility of lateral-flow urine lipoarabinomannan for tuberculosis diagnosis in HIV-infected African adults

Abstract

Setting: In-patient hospitals in South Africa and Uganda.

Objective: To evaluate the cost-effectiveness of a lateral-flow urine lipoarabinomannan (LAM) test when added to existing strategies for tuberculosis (TB) diagnosis in human immunodeficiency virus infected adults (CD4(+) T-cell counts < 100 cells/l) with symptoms of active TB.

Design: Decision-analytic cost-utility model, with the primary outcome being the incremental cost-effectiveness ratio, expressed in 2010 US dollars per disability-adjusted life year (DALY) averted from the perspective of a public sector TB control program.

Results and conclusion: For every 1000 patients tested, adding lateral-flow urine LAM generated 80 incremental appropriate anti-tuberculosis treatments and averted 224 DALYs. Estimated cost utility was US$353 per DALY averted (95% uncertainty range $192$1161) in South Africa and $86 per DALY averted (95% uncertainty range $49$239) in Uganda, reflecting the lower treatment costs in Uganda. Cost utility was most sensitive to assay specificity, cost of anti-tuberculosis treatment, life expectancy after TB cure and cohort TB prevalence, but did not rise above $1500 per DALY averted in South Africa under any one-way sensitivity analysis. The probability of acceptability was >99.8% at a per-DALY willingness-to-pay threshold equal to the per capita gross domestic product in South Africa ($7275) and Uganda ($509).

Figure 1. Cost-effectiveness Acceptability Curves for Lateral-Flow Urine LAM Detection

Curves show the probability of cost-effectiveness (cost per DALY averted lower than the value on the x-axis) of urine LAM, over 10,000 Monte Carlo simulations. Black lines show cost-effectiveness in South Africa (where TB treatment is more expensive); grey lines represent Uganda (where TB treatment is cheaper). Solid lines utilize a baseline in which smear and other non-bacteriological diagnostics (e.g., chest X-ray) are available, but not Xpert MTB/RIF; dotted lines assume that Xpert MTB/RIF is also available.

Figure 2. Sensitivity Analysis: Cost-Utility of Lateral-Flow Urine LAM Detection in South Africa

The vertical line represents the base-case scenario ($353 per DALY averted, see also Table 2). The black bars represent the incremental cost-effectiveness ratio at the low value of the sensitivity range for each parameter (Table 1), and the white bars represent the same ratio at the high value of the range.

Figure 3. Three-way Sensitivity Analysis: Effect of Assay Specificity, TB prevalence, and Life Expectancy after TB cure in South Africa

Cost-utility of lateral-flow urine LAM, according to specificity, TB prevalence, and life expectancy after TB cure in South Africa. Grey shading indicates that the existing diagnostic strategy (without Xpert MTB/RIF) would be preferred at a willingness to pay (WTP) of $7,275, while white shading indicates that addition of lateral-flow urine LAM would be preferred at this WTP threshold. Thus, for example, assuming a life expectancy of 1.5 years and assay specificity of 95%, lateral-flow urine LAM would be the preferred testing strategy in South Africa if deployed in populations with a probability of finding active TB that is greater than 5% (panel A, transition from white to grey).