Careful which colour you choose

TAKING your medicine even for a week is a drag. Taking it every day for six months is a real nuisance. Yet that is what is asked of those being treated for tuberculosis. They need to pop their pills for half a year if they are to eliminate the bacteria that cause the infection and combat the emergence of antibiotic-resistant strains. Worse, from the point of view of compliance, the actual symptoms of infection tend to go away after just two months of taking the medicine, so the incentive to carry on is negligible. But worse than that, the drugs themselves produce unpleasant symptoms, including nausea, diarrhoea, headaches and insomnia. Indeed, one common anti-TB drug, rifampicin, also has the unnerving side effect of turning people's tears, sweat and urine a shade of reddish orange.

Every cloud, though, has a silver lining, for it was this strange, if harmless, side effect that gave a team of researchers at the Massachusetts Institute of Technology (MIT) their crucial idea: stamp-sized patches, much like litmus paper, that change colour when exposed to the urine of people with traces of medicine in their systems. The crucial trick of XoutTB, as the system built around these patches is known, is that the change in colour reveals a code that a patient can text-message to a service which rewards him with free airtime minutes on his mobile phone. Patients thus have a daily incentive to take their terrible pills.

The XoutTB project began in the spring of 2007, with the launch of the Yunus Challenge, a now-annual contest at MIT to promote development in poor countries. Muhammad Yunus, after whom the challenge is named, is a Nobel Prize-winning pioneer of microfinance—the idea that loans too small for traditional banks to handle are nevertheless crucial in enabling businesses to flourish in the poorer parts of the world.

The winner of that year's challenge was the team led by Jose Gomez-Marquez, a medical engineer at MIT. Their original idea, inspired by Dr Yunuss work, was to involve local banks (in this case in Nicaragua) in a scheme that would give TB patients micro-loans in exchange for evidence that they had been taking their medication. That plan fell by the wayside because the banks did not want to get involved. But phone companies were willing to give it a try, and brought with them the bonus of an established infrastructure for distributing the rewards. The resulting trial, which involved 30 people with tuberculosis, was a success, and a second is about to be carried out in Pakistan, where a batch of 400 XoutTB patches is arriving this month.

Conditions in Karachi, the Pakistani city in which the trial is being conducted, could politely be described as “challenging”. According to Rachel Glennerster, a member of the XoutTB team who has worked as an economist at the IMF and the British Treasury, the local clinics are closed about 60% of the time and doctors or nurses are often absent during the 40% when the doors are nominally open. Such absences—and the associated lack of compliance-monitoring—are one of the things for which XoutTB is designed to compensate.

Pakistan, though, offers a second difficulty. Aamir Khan, the director of XoutTB's operations in the country, has quickly discovered that one of the neediest groups of people there are 15- to 25-year-old women. Unfortunately, they are often under the thumbs of their parents or husbands and are not allowed mobile phones of their own. Dr Khan is therefore considering the idea of a different reward—high-energy food supplements to combat malnutrition. The system would not supply food, per se, but would instead top up credit at the patient's grocer using an automatic link.

If XoutTB does work, the team has ambitions to extend it. Other drugs, too, can be a nuisance to remember. The anti-retrovirals used to combat AIDS, for example, have to be taken for the rest of a patient's life. And taking medicines for non-infectious conditions such as diabetes and high blood pressure is also a chore. Find the right “litmus test”, though, and what is now being done with TB drugs could succeed with any of these as well. Taking your medicine could, at last, become a truly rewarding experience.