Compared to traditional tests using a microscope, GeneXpert is more accurate and much quicker in diagnosing tuberculosis, and can detect drug resistant strains of the disease. But are the high costs worth it?
When Londoner Steve Bradley fell ill, his doctors were baffled. In desperation, they gave him a cocktail of toxic drugs. Eventually, they discovered he had drug resistant TB. The drugs left him nearly blind and unable to walk properly.
I was in intensive care for ten days, and it took the full ten days for them to find I had TB. I think if I'd been diagnosed quicker I'd be back to what we call a normal human being, and basically get into the normal run of lifestyle again, but obviously that's not going to happen for me.
In the UK, TB rates have been rising for 20 years, up to 10,000 cases annually. Since half of them occur in London, it's been called the TB capital of Europe. But diagnosing the disease is a big problem around the world. Now a system is being rolled out that can diagnose TB in just two hours. It's a fusion of existing technologies that can detect the telltale genetic signature of the bacteria.
DR. TIM MCHUGH [University College London]
The GeneXpert represents a major step forward; not in the biochemistry of it, but in the technology that surrounds that, the means of processing the sample and detecting the result.
Compared to traditional tests using a microscope, GeneXpert is more accurate and much quicker. And it can detect drug-resistant strains of the disease. That's a big advantage in poorer countries like here in South Africa, where drug resistance is growing. Fast diagnosis can also slow the spread of the disease. It's estimated that, without treatment, TB patients infect at least ten other people a year. But these advantages come at a price.
DR. TIM MCHUGH
Although it's a robust technology, it's a relatively expensive technology. So to prepare a smear on a slide, the major cost is likely to be the person who's reading that slide. With this machine, in sub-Saharan Africa they're selling the cartridges for USD$20 dollars. But USD$20 dollars is a substantial amount of money for a diagnosis.
That's ten times the cost of the old slide test. The cartridges cost even more in richer countries -- about USD$70 dollars. And with the machine itself priced at USD$80,000 dollars, it's a big investment, even for well-off healthcare systems. The price will be lower for poorer countries, but there are other problems. Without a laptop computer and a reliable power supply, the machine can't work.
DR. BERTIE SQUIRE [Liverpool School of Tropical Medicine]
If we don't get it right with implementing GeneXpert, and working out exactly what it will take, it will just add to the dusty pile of equipment in the corner.
So rich and poor countries alike need independent assessments to find out if new technologies like this are cost-effective. This computer model, created by Bertie Squire and his team, should help.
DR. BERTIE SQUIRE
What we've been trying to do is think about the kind of evidence that a national policy maker or a hospital of a clinic would like to see before it made the decision to buy GeneXpert or any other diagnostics. We've developed a system which can model the effects of diagnostic systems in terms of the number of patients being diagnosed, in terms if the costs, the training requirements and actually project what those would look like over a decent period of time, say, ten plus years.
The results of this and other trials may determine whether GeneXpert is a good investment or a technological dead end. Whatever outcome, it's too late for patients like Steve.
It would have changed my life. I'd still have been able to work, still be able to continue after the blip of health problems, and get back to a normal working life, which I don't have anymore.