Why the global poor need a new TB test, and why this one might not be it

TB patient and physician, El Salvador

tuberculosis patient, El Salvador

I’m a little slow off the mark here but wanted to note the new “TB testing machine,” as the ONE blog called it, and why the world needs a better tuberculosis test.

Yesterday, the World Health Organization “endorsed” and heralded as a “major milestone” a new DNA fingerprinting machine called XpertMTB/RIF, developed by the biotech firm Cepheid with support funding from the Bill & Melinda Gates Foundation and the NIH. A Gates funded non-profit organization called FIND, Foundation for Innovative and New Diagnostics, helped Cepheid develop the test.

Given all the hoopla about this being a major advance in the fight against global TB, I hesitate to ask if this approach will really work for the people who need it most — those living in poor communities where hospitals don’t have enough money to give nurses masks, let alone drugs or state-of-art diagnostics.

For poor countries, this high-tech TB test sounds pretty expensive.

But first, as NPR’s Scott Hensley reports, the problem with the standard approach to TB diagnosis is that:

Current practice in many less-developed countries is a test, more than 100 years old, that involves analyzing a sputum sample under a microscope. That can miss TB — especially in kids and people with HIV. It also doesn’t help determine whether the TB is resistant to conventional drug treatment. That takes a separate, more time-consuming culture.

TB is one of the world’s biggest killers, claiming something like 5,000 people a day. One of every three people on the planet carry this bug and drug-resistant TB is on the rise. As Reuters reports:

TB hits mostly poor people in developing regions such as sub-Saharan Africa, India and China, but also occurs in poor regions of developed nations and is common in patients with the human immunodeficiency virus (HIV) that causes AIDS. The WHO estimates that 9.4 million people developed active TB in 2009 and the disease killed 1.7 million in that year. The emergence of drug-resistant and extensively drug-resistant forms of TB is also a growing global problem.

TB patient and physician, El Salvador

Part of the reason tuberculosis is one of the world’s leading killers, is spreading and developing drug resistance is that people don’t get treated early enough in the course of the infection. Better and quicker diagnosis should, in theory, help get people on treatment sooner to stop them spreading this contagion.

Cepheid’s Xpert DNA testing device is indeed a medical and technical breakthrough, a major improvement in TB diagnosis since it allows testing to be done in minutes as opposed to today’s approach, which can take weeks or months to complete. Studies show it is also much more precise.

In the rich world, Cepheid says it intends to sell Xpert for something like $60,000 and the tests likely to cost around seventy dollars (though, for some reason, the firm reportedly has not yet sought U.S. licensure from the FDA).

In poor countries, company spokespeople say they will discount the cost of Xpert to $17,000 to bring down the tests to something like $15.

That may not sound like much but most of these poor countries lack money to purchase basic medical supplies like masks and gloves. The ministries of health in many developing countries balk at buying vaccines that cost a dollar or more.

The WHO says the cumbersome TB lab testing methods used today cost about the same over time and the Xpert testing system should save money in the long run. That makes sense to me, but it may not be enough to convince those who need this test the most that it is worth spending on one diagnostic test what some of these poor countries spend per person per year on health care overall.

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Tom Paulson

Tom Paulson is founder and lead journalist at Humanosphere. Prior to operating this online news site, he reported on science,  medicine, health policy, aid and development for the Seattle Post-Intelligencer. Contact him at tom[at]humanosphere.org or follow him on Twitter @tompaulson.