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WHO framework targets tuberculosis–diabetes link

2011; Elsevier BV; Volume: 378; Issue: 9798 Linguagem: Inglês

10.1016/s0140-6736(11)61527-4

1474-547X

John Maurice,

Chronic Disease Management Strategies

The global diabetes epidemic could be thwarting efforts to combat tuberculosis. But WHO and its partners plan to take remedial action with the launch of a new framework. John Maurice reports. In the 1990s, the anti-tuberculosis community realised that HIV/AIDS contributed to a substantial increase in tuberculosis cases. Their reaction was to call on tuberculosis and HIV/AIDS programmes to join hands in tackling both diseases. In 2007, the anti-tuberculosis community decided to do something about tobacco smoking, which according to study findings was the reason for an even greater proportion of tuberculosis cases. Their reaction was to appeal to tobacco control programmes to join tuberculosis programmes in tackling both scourges. Over the next few months, in what might well be their most ambitious reaction yet, the anti-tuberculosis community will seek to join forces with the anti-diabetes community. For what is probably the first time, a major communicable disease is joining up with a major non-communicable disease. Prompting this reaction is the evidence, obtained in late 2010, that the burgeoning diabetes epidemic is the cause of a large number of new tuberculosis cases. The reaction of the anti-tuberculosis coalition will take the form of a . It has two aims, says Mario Raviglione, head of the WHO's Stop TB department. “On an individual level, we hope it will increase the number of people receiving timely, accurate diagnosis and proper treatment for the two diseases. On a public health level, we hope it will help to reduce the incidence of the two diseases.” On the public health level, the diabetes epidemic could be one reason why efforts to reduce the global incidence of tuberculosis are having little effect despite high case detection rates and cure rates. “We're detecting a global average of about 65% of the estimated number of new tuberculosis cases and we're curing 86% of them”, says Raviglione. “With these percentages, we should be lowering tuberculosis incidence by 5–10% a year according to mathematical modelling. Since 2004, the incidence is falling steadily, but by only 1% or so a year. We have a real problem.” There is little doubt that the diabetes epidemic is partly to blame for the problem. Knut Lönnroth, specialist in social determinants, risk factors, and comorbidities of tuberculosis with the Stop TB department and lead author of the new framework, says: “We now know that diabetes increases by threefold the risk of a person developing tuberculosis. We estimate that it is contributing to about 8% of new tuberculosis cases annually.” Diabetes, he says, also increases the risk that a patient's response to tuberculosis treatment will be delayed, or that the patient will die during tuberculosis treatment, or that tuberculosis will relapse after completion of treatment. “The net effect”, he says, “is that the diabetes epidemic is hampering efforts to control tuberculosis”. Other factors that could be sustaining the incidence of tuberculosis include a failure to diagnose enough people infected with multidrug-resistant tuberculosis. But for WHO and its partners the core of the problem is that, as Raviglione puts it, “we're just not picking up cases of active tuberculosis early enough”. Tuberculosis progresses slowly and many months might elapse before symptoms appear or become severe enough to force a patient to seek medical advice. During those months, an untreated person with active infection will infect an average of ten to 15 other people. “We can't screen the whole world population to detect and treat tuberculosis patients before they infect the community”, says Raviglione. “So we're focusing on the vulnerable groups with risk factors for tuberculosis.” Quantifying these risk factors was a central objective of a series of systematic reviews undertaken by WHO and its partners in 2008 and 2009. The reviews estimated the proportions of active tuberculosis cases attributable to six major risk factors for tuberculosis in 22 countries where the disease is highly prevalent. Taken together, these countries account for about 80% of the world's tuberculosis cases. The risk factors studied were diabetes, HIV infection, malnutrition, alcohol use, smoking, and indoor air pollution (table).TableMajor risk factors for tuberculosis: weighted average for 22 high-burden countriesRelative risk of active tuberculosisGlobal prevalence rate (total population)Population attributable factor (total population)*Population attributable factor (percentage of tuberculosis cases attributable to the risk factor).HIV infection26·70·8†For 15–19 year age group.11·0Malnutrition3·216·726·9Diabetes3·15·47·5Alcohol use >40 g/day2·98·1‡For adults. Source: Lancet 2010; 375: 1814–29.9·8Smoking2·026·5‡For adults. Source: Lancet 2010; 375: 1814–29.15·8Indoor air pollution1·571·222·2* Population attributable factor (percentage of tuberculosis cases attributable to the risk factor).† For 15–19 year age group.‡ For adults. Source: Lancet 2010; 375: 1814–29. Open table in a new tab HIV, which is associated with a nearly 30-times relative risk of tuberculosis and contributes to an estimated 11% of new active tuberculosis cases, was an obvious first choice for a collaborative framework. Smoking, which accounts for nearly 16% of new tuberculosis cases, was also a logical target. Diabetes, which accounts for 8% of cases, was a less obvious choice. Raviglione explains: “As a risk factor, diabetes is certainly not in the same ballpark as HIV but it has a lot going for it as a target for us. It currently affects at least 5% of the world's population, or close to 380 million people. And that number is growing rapidly. What's more, like HIV-infected people, a large proportion of people with diabetes come to clinics, physicians' offices, health centres, and so on. They are therefore readily accessible to screening. How do you reach large numbers of alcohol abusers? The malnourished? People using indoor stoves?” Diabetes might not be in the same risk factor league as HIV but the 8% of new cases of active tuberculosis attributable to diabetes amounts to more than 700 000 cases per year worldwide—cases that would not have occurred in the absence of diabetes. Moreover, in eight of the 22 countries with a high prevalence of tuberculosis, diabetes accounts for a greater proportion of tuberculosis cases than does HIV. Of the eight countries, some are heavily populated—Russia, for example, where diabetes accounts for 14% of tuberculosis cases (vs 11% for HIV), India 23% (vs 5%), and Pakistan 9% (vs 1·5%). What is more, the diabetes epidemic is only just starting to escalate. The number of people with diabetes in the world is likely to reach 438 million by 2030, up from 151 million in 2000, according to the International Diabetes Federation. The new framework sets out mechanisms for linking up detection and care activities for the two diseases at all levels of health care in all countries where the two diseases are prevalent. Screening will be central to the collaboration. “Doctors and other health-care providers will have to crank up their level of suspicion when seeing a patient with either diabetes or tuberculosis”, says Raviglione. “That shouldn't be a problem. Initial screening for tuberculosis in a diabetes patient will take just a few basic questions: Have you been coughing for more than 2 or 3 weeks? Have you had fever? Do you sweat at night? And a rapid blood sugar test would be enough to suggest whether or not a tuberculosis patient has diabetes.” Such initial screening is the least costly and most manageable way to identify these diseases, Lönnroth says. As the framework points out, though, more specific and sensitive diagnostic tests may be warranted if resources are available. “Screening for comorbidities in patients with tuberculosis or diabetes is really part of normal medical practice”, he says. The trouble is that in areas where one of the two diseases is not prevalent, doctors might not remember to screen. They might also have forgotten what they learned as medical students about the link between tuberculosis and diabetes. “We would like the framework to jog their memories and to ensure that screening for the two diseases becomes integrated into government policy in all countries.” Ministers of health will be the first recipients of the framework. “We want the ministers to establish the link all the way down, from regions, districts, communities, and right down to the primary health care centres”, says Raviglione. The framework will also be given to public health and professional medical associations, who will be asked to convince their members to follow the framework's guidelines. Some countries are already expressing interest, among them Brazil, China, India, Mexico, and Sri Lanka. These countries could be among the first to field test the framework. One issue awaits clarification. If screening for latent tuberculosis infection turns up a case, should the patient be put on antibiotic prophylaxis? WHO recommends that preventive isoniazid treatment be given to tuberculosis patients living with HIV and to children younger than 5 years who have been living in close contact with a patient who has active tuberculosis. For a patient with diabetes suspected of having latent tuberculosis infection, WHO has not, for lack of robust scientific evidence, issued recommendations about chemoprophylaxis. From the diabetes perspective, Shanthi Mendis, coordinator of chronic disease prevention at WHO, points out that tuberculosis in a diabetes patient is likely to be only one of a lengthy list of possible ailments the patient faces—cardiovascular disease, renal failure, neurological complications, and retinopathy, to name only a few. Nevertheless, the collaborative framework proposed by the tuberculosis coalition will, she believes, play a useful part in integrating diabetes and tuberculosis control at all health-care levels, but particularly at the primary health-care level. “It should prompt ministers to ensure that all levels of the health workforce, including ancillary health workers, are trained to screen for the two diseases and that basic diagnostic and therapeutic facilities are available to manage both diseases.” Her concern, though, is that “the framework may encourage people to consider just these two diseases: other chronic respiratory diseases, such as asthma, can coexist with tuberculosis and confound the diagnosis”. To which Lönnroth responds: “We need to start somewhere. We started with HIV and smoking. Now, we're on the way with diabetes. And more synergies with more risk factors may follow in the future.”