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This is a summary of a review article titled, 'Addressing diabetes mellitus as part of the strategy for ending TB' published in Royal Society of Tropical Medicine and Hygiene. This article is written by Anthony D Harries, Ajay M V Kumar, Srinath Satyanarayana, Yan Lin, Rony Zachariah, Knut Lonnroth and Anil Kapur.

Introduction

The new Sustainable Development Goals (SDGs) has 17 goals and 169 targets, there is one goal under SDG 3 for Health and it has 13 targets under it. The third target (SDG 3.3) is focused on ending epidemics of the major communicable diseases such as AIDS, TB and malaria, and neglected tropical diseases by 2030, while the fourth target (SDG 3.4) is focused on reducing by one-third premature mortality from non-communicable diseases through prevention and treatment.

Tuberculosis (TB)

Statistically about one-third of the world’s population is estimated to be infected with Mycobacterium tuberculosis, and between 5 and 10% of infected persons are at risk of developing active TB during their lifetime. In 2014, an estimated 9.6 million people developed new active TB and 1.5 million people died from the disease, 390 000 of whom had associated HIV infection. Globally, about 6 million TB cases were notified and reported to WHO, leaving 3.6 million cases un reported. The burden of TB is highest in Asia and Africa, with India and China together accounting for almost 40% of the world’s TB cases. HIV is the strongest known risk factor for the development of TB and globally 1.2 million people were estimated to develop HIV-associated TB in 2014. However, only 51% of TB patients had a documented HIV test result. There are several other important determinants of the TB epidemic, one of which is Diabetes Mellitus.

Diabetes Mellitus (DM)

Diabetes mellitus (or diabetes) is a chronic, lifelong condition that affects your body's ability to use the energy found in food. In 2013, it was estimated that 382 million people worldwide had DM, with 90% or more having Type 2 disease. About 80% of these people live in low- and middle-income countries (LMIC), and if the trends of the past 10–15 years continue with 10 million new cases occurring every year, an estimated 592 million people will have DM by 2035. DM is common in the age group 40–59 years, however, DM is increasingly being seen in younger persons especially in LMIC. Due to the association between DM and lifestyles such as unhealthy diets and physical inactivity, there are more people with DM in urban areas compared with rural areas. Asia is the global region most affected by DM. China and India are the two countries with the highest prevalence of DM, with 98.4 million and 65.1 million people aged 20–79 years estimated to have the disease. Other high burden Asian countries include Indonesia, Japan, Pakistan, Bangladesh, Malaysia and the Philippines.

Association of TB and DM

 A study has confirmed that the overall risk of TB in persons with DM is three times higher than in the general population. Both type 1 and type 2 DM can increase the risk of TB, but as type 2 disease accounts for 90% or more of the global cases of DM, the public health burden of co-morbid disease from type 2 DM is by far more worrying. There is also growing evidence that patients with uncontrolled hyper glycaemia are at higher risk for TB than those with controlled blood glucose levels suggesting that hyper glycaemia is an important determinant in this interaction. DM not only increases the risk of developing active TB but also adversely affects TB treatment outcomes. Further it was observed that DM increases the risk of death during TB treatment. Finally, there is growing evidence that in persons with DM poor glycaemia control adversely affects TB treatment outcomes, and that smoking more than one pack of cigarettes per day significantly increases the risk of death in patients with dual disease.

Addressing diabetes as part of the End TB Strategy

Within the End TB Strategy, there are a number of actions that can be taken to mitigate the effect of DM on increasing the burden of TB. These can be explained with the help of 3 pillar model of End TB strategy.

Pillar 1

The first pillar encompasses the four main technical interventions around early diagnosis, treatment and management of co-morbidities and preventive therapy for latent TB infection. Ensuring early TB diagnosis requires that people who need to be investigated for TB are swiftly identified by health care providers. Among TB patients, there are several benefits of identifying undiagnosed DM (and thus contributing to reducing the large pool of un-diagnosed DM patients) and offering DM treatment to prevent or delay diabetes-related complications and improve TB treatment outcomes. TB patients could be routinely screened for DM at the time of registration by asking first about whether there was a known diagnosis of DM and, in those saying no, performing random blood glucose measurements

Pillar 2

The second pillar focuses on health and social policies and systems required to deliver essential health interventions, social protection and actions to address the social determinants of TB. Adequate financing, government stewardship, appropriate health regulations, programmatic planning based on epidemiological surveillance, and engagement of all relevant governmental and non-governmental stakeholders are essential for ensuring universal health coverage, high-quality integrated patient-centered care, and financial risk protection for patients. Currently, most patients with DM and TB are cared for separately by their respective programs. For patients with DM and TB, the management of both diseases would best be centered at the TB clinic during the entire length of TB treatment, but this needs discussion, education, training and resources directed at staff in charge of TB clinics. DM is an important population-level determinant of TB. If the prevalence of diabetes continues to increase at the present rate, this is likely to severely hamper the reduction of global TB incidence. Public health programs focusing on communicable and non-communicable diseases, need to join forces to identify synergistic public health actions, including addressing shared social determinants.

Pillar 3

The third pillar focuses on research and innovation. There are serious limitations around current service delivery for TB, which includes diagnostic technology, treatment of MDR-TB and preventive therapy, which make the third pillar of the End TB Strategy that focuses on innovation and research essential for success. An important cornerstone of good TB control programs is the standardized monitoring and evaluation system with quarterly reporting of cases and treatment outcomes and it has been relatively easy to build into this system a monitoring and evaluation framework for DM screening, similar to what is currently being done for HIV/AIDS and antiretroviral therapy.

Conclusion

This is the first time ever attempt has been made to reduce morbidity and mortality from both communicable and non-communicable diseases together. Collaborative care for patients with DM and TB offers a way to formulate a better public health approach for the prevention, diagnosis and care of non-communicable diseases and will be mutually beneficial.  In high burden TB countries, the inclusion of DM in the strategic plan to end TB will become increasingly important in the next few years. More research and evidence is required in this area. Integration of DM and TB services and infection control could lead to better and earlier TB case detection, more successful TB treatment outcomes and improved TB prevention.