Xpert TB test very cost-effective in South Africans starting ART
Two Xpert Mycobacterium tuberculosis rifabutin resistance assays in South Africans starting antiretroviral therapy (ART) would be highly cost-effective, according to a cost-benefit modeling analysis using a hypothetical South African population.
Undiagnosed TB prevalence ranges from 15% to 30% among HIV-positive people starting ART in regions with high TB prevalence. These people are usually screened for TB by symptoms and sputum smear, which have poor sensitivity for detecting TB infection. To determine whether the Xpert test and other approaches would prove cost-effective in screening patients starting ART, researchers conducted this modeling study.
The model considered all patients and only patients with TB symptoms in hypothetical South African cohorts starting ART with an average CD4 count of 171 cells/μL and TB prevalence of 22%. The model simulated no active screening and four diagnostic strategies: smear microscopy (sensitivity 23%); smear and culture (sensitivity 100%); one Xpert test (sensitivity in smear-negative TB 43%); two Xpert tests (sensitivity in smear-negative TB 62%).
Because South Africa has a gross domestic product of $7100 per capita, the researchers set that as the cutoff for determining whether a diagnostic strategy is cost-effective.
Compared with no TB screening, screening symptomatic patients with sputum smear would increase life expectancy by 1.6 months. Using two Xpert screens in all patients would increase life expectancy by 6.6 months.
If TB prevalence is 22%, the incremental cost-effectiveness ratio of sputum smear for all patients is $2800 per life-year saved, while the incremental cost-effectiveness ratio for two Xpert tests for all patients is $5100 per life-year saved—well below the $7100 cost-effectiveness cutoff. Using only one Xpert sample or only symptom screening was less efficient.
The researchers conclude that their model-based analysis “suggests that screening all individuals initiating ART in South Africa with two Xpert samples is very cost-effective.”
Source: Jason R. Andrews, Stephen D. Lawn, Corina Rusu, Robin Wood, Farzad Noubary, Melissa A. Bender, C. Robert Horsburgh, Elena Losina, Kenneth A. Freedberg, Rochelle P. Walensky. The cost-effectiveness of routine tuberculosis screening with Xpert MTB/RIF prior to initiation of antiretroviral therapy: a model-based analysis. AIDS. 2012; 26: 987-995.
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