New TB Test Is Worth the Cost
A 10- and 20-year projection finds that the Xpert MTB/RIF tuberculosis test currently recommended by the World Health Organization is worth the economic and healthcare costs in south Africa.
-- by Nina Lincoff
Tuberculosis, or TB, has been a dangerous disease for centuries. Adding to its sinister legacy is the fact that it thrives in places where humans endure the poorest of living conditions. Lack of light, clean water, clean air, and extreme crowding—think urban slums—is the prime turf for TB. It is an infectious disease caused by the bacteria Mycobacterium tuberculosis, and manifests as cough, fever, weight loss, loss of breath, and expulsion of mucus (sputum).
In 2010, there were an estimated nine million new cases of TB and 1.5 million TB-related deaths. Because of the prevalence of TB in parts of the world with inadequate healthcare, detection and prevention of TB has been a long and complicated process. Although the World Health Organization (WHO) has taken steps towards improving TB outcomes, the lack of proper diagnostic tools threatens positive progress.
But a relatively new automated DNA test known as Xpert MTB/RIF could change the time line for accurate and sensitive detection of TB. Xpert utilizes a cartridge-based system that can be successfully administered by even relatively unskilled healthcare workers. Better yet, results are ready in less than two hours and are more than 98 percent accurate in patients with smear-positive TB, and 70 percent accurate in patients with smear-negative TB. WHO currently recommends Xpert for first diagnosis of suspected TB and HIV-associated TB patients.
Accuracy and ease of use make the Xpert TB detection test ideal for use in countries with insufficient healthcare infrastructure. However, the cost and human impact of such tests are imperative to their successful adoption on a large scale.
Researchers from Harvard University evaluated the health and economic consequences of Xpert in five African countries where TB-HIV coinfection is prevalent—Botswana, Lesotho, Namibia, South Africa, and Swaziland—and projected a 10- and 20-year estimation of the effects of Xpert. They estimate that implementation of Xpert avoids over 180,000 TB deaths in southern Africa. However, healthcare cost would increase by 460 million USD. But the upside may be worth it.
The ramifications of system cost will have to be compared with the possible prevention of TB cases and TB-related deaths before the utility of Xpert can be determined.
The Expert Take
While research suggests that Xpert is "cost-effective by conventional benchmarks, it's not the slam-dunk we thought we might see," said study-author Nick Menzies, Ph.D. "It turns out that while adopting this test should do a lot to improve TB outcomes in this region, it will also put considerable strain on healthcare resources, particularly for treatment of drug-resistant TB."
The key feature of Xpert when compared to the current diagnostic test is that Xpert is tremendously more sensitive. When detecting a disease, this sensitivity is imperative to successful patient outcome. "Current diagnosis is hampered by the fact that many individuals with active TB will be missed, even if they attend a health center reporting TB symptoms," says Menzies. Missed diagnosis is even more prevalent in parts of the world with high HIV-associated TB.
Source and Method
Researchers calibrated a scenario to estimate the potential economic and healthcare ramifications of a Xpert roll-out. This scenario was contrasted with the current diagnostic approach which relies on a sputum smear test. These projections were extended over a 10- and 20-year period.
With any roll-out of a new test or treatment, the widespread economic and healthcare effects must be weighed against any potential positive patient outcome gains. The study of WHO’s recommended Xpert test finds that the positives of adopting Xpert outweigh the economic and healthcare negatives.
However, the financial burden will be substantial and because of the influence of HIV in the region studied, widespread adoption of Xpert in areas without high HIV prevalence should be considered, the researchers said.
Researchers reported in The Lancet earlier this month that Xpert MTB/RIF is a sensitive and accurate way to rapidly diagnosis pulmonary tuberculosis in children. However, the participant pool was sourced form Zambia and therefore cannot be accurately generalized.