The challenge of worldwide tuberculosis control: and then came diabetes

Diabetes increases the risk of developing tuberculosis and adverse treatment outcomes.1Pan SC Ku CC Kao D Ezzati M Fang CT Lin HH Effect of diabetes on tuberculosis control in 13 countries with high tuberculosis: a modelling study.Lancet Diabetes Endocrinol. 2015; 3: 323-330Summary Full Text Full Text PDF PubMed Scopus (62) Google Scholar, 2Odone A Houben RMGJ White RG Lonnroth K The effect of diabetes and undernutrition trends on reaching 2035 global tuberculosis targets.Lancet Diabetes Endocrinol. 2014; 2: 754-764Summary Full Text Full Text PDF PubMed Scopus (84) Google Scholar Diabetes prevalence is increasing rapidly, particularly in low-income and middle-income countries with the highest burden of tuberculosis.1Pan SC Ku CC Kao D Ezzati M Fang CT Lin HH Effect of diabetes on tuberculosis control in 13 countries with high tuberculosis: a modelling study.Lancet Diabetes Endocrinol. 2015; 3: 323-330Summary Full Text Full Text PDF PubMed Scopus (62) Google Scholar Modelling studies have estimated that a 25% increase in prevalence of diabetes worldwide would increase the incidence of tuberculosis by 8% by 2035.2Odone A Houben RMGJ White RG Lonnroth K The effect of diabetes and undernutrition trends on reaching 2035 global tuberculosis targets.Lancet Diabetes Endocrinol. 2014; 2: 754-764Summary Full Text Full Text PDF PubMed Scopus (84) Google Scholar Undiagnosed and poorly controlled diabetes could therefore create an extra strain to tuberculosis care and prevention.3Lönnroth K Roglic G Harries AD Improving tuberculosis prevention and care through addressing the global diabetes epidemic: from evidence to policy and practice.Lancet Diabetes Endocrinol. 2014; 2: 730-739Summary Full Text Full Text PDF PubMed Scopus (162) Google Scholar In The Lancet Global Health, Jean Jacques Noubiap and colleagues4Noubiap JJ Nansseu JR Nyaga UF et al.Global prevalence of diabetes in active tuberculosis: a systematic review and meta-analysis of data from 2·3 million patients with tuberculosis.Lancet Glob Health. 2019; (published online Feb 25.)http://dx.doi.org/10.1016/S2214-109X(18)30487-XSummary Full Text Full Text PDF PubMed Scopus (70) Google Scholar describe the results of a systematic review and meta-analysis of data from 2·3 million patients with tuberculosis from 50 countries. They included pulmonary and extrapulmonary tuberculosis cases extracted from observational studies, as well as patients with diagnosis of diabetes using various criteria (physician diagnosis, laboratory, or self-report). The investigators found a high burden of diabetes among patients with active tuberculosis (pooled prevalence of diabetes 15·3%, 95% predictive interval 2·5–36·1). The prevalence of diabetes was lower in low-income countries and those with low Human Development Index, and higher in countries with low tuberculosis burden. Diabetes burden among patients with active tuberculosis tended to be higher with increasing age and among men, but did not differ with type of tuberculosis, with presence of HIV, or between hospital-based and community-based studies. The investigators pooled data from 200 observational studies (cross-sectional, case control, and cohort studies). They observed a wide variability in the estimate across countries, largely due to the substantial heterogeneity across the studies, variation in the diagnosis criteria, and risk of bias among populations studied. The diagnostic method of diabetes explained nearly half (49·3%) of the heterogeneity of the prevalence, and showed even wider variability in the pooled estimates. For some countries, estimates were based on single, small studies, which could affect generalisability. The systematic review showed a very high prevalence of diabetes occurring among patients receiving treatment for tuberculosis in low-resource settings, including Africa. The pooled estimate for these patients was nearly twice as high as in general adult population. These results are probably overestimates, because (as the authors note) the occurrence of diabetes was determined often by a single blood glucose test, which could just be transient hyperglycaemia among newly diagnosed patients with tuberculosis.5Boillat-Blanco N Ramaiya KL Mganga M et al.Transient hyperglycemia in patients with tuberculosis in Tanzania: implications for diabetes screening algorithms.J Infect Dis. 2016; 213: 1163-1172Crossref PubMed Scopus (66) Google Scholar The extent of bias is unclear, but even if diabetes prevalence is lower than these estimates, it would still represent a huge burden, particularly for low-resource settings. Data from general populations on the prevalence of diabetes are susceptible to similar potential bias,6Jaffar S Diabetes and other non-communicable diseases in Africa: a potential disaster in the waiting.Lancet Diabetes Endocrinol. 2016; 4: 875-877Summary Full Text Full Text PDF PubMed Scopus (7) Google Scholar but point to a high and rising prevalence of diabetes in Africa,7Atun R Davies JI Gale EAM et al.Diabetes in sub-Saharan Africa: from clinical care to health policy.Lancet Diabetes Endocrinol. 2017; 5: 622-667Summary Full Text Full Text PDF PubMed Scopus (228) Google Scholar and, moreover, that health service provision for the management of diabetes is very poor in Africa. This finding, along with various previous modelling studies,1Pan SC Ku CC Kao D Ezzati M Fang CT Lin HH Effect of diabetes on tuberculosis control in 13 countries with high tuberculosis: a modelling study.Lancet Diabetes Endocrinol. 2015; 3: 323-330Summary Full Text Full Text PDF PubMed Scopus (62) Google Scholar, 2Odone A Houben RMGJ White RG Lonnroth K The effect of diabetes and undernutrition trends on reaching 2035 global tuberculosis targets.Lancet Diabetes Endocrinol. 2014; 2: 754-764Summary Full Text Full Text PDF PubMed Scopus (84) Google Scholar suggest an increasing burden of diabetes among patients with tuberculosis. We do not know whether tuberculosis led to the increase in diabetes or whether diabetes led to tuberculosis in these cases. What we do know is that these two conditions occur together and that the rising prevalence of diabetes is threatening tuberculosis control, as HIV has done. Tuberculosis control was doing well, and then along came HIV. We are just about managing to control HIV now, which will help tuberculosis control. But then along comes diabetes. The effect of diabetes on tuberculosis control is now clearer. We now need urgently to improve screening and treatment of diabetes among patients with tuberculosis. Given scarce human and financial resources, innovative models of care are required to mitigate the dual burden of diabetes and tuberculosis, including use of platforms developed for HIV infection.3Lönnroth K Roglic G Harries AD Improving tuberculosis prevention and care through addressing the global diabetes epidemic: from evidence to policy and practice.Lancet Diabetes Endocrinol. 2014; 2: 730-739Summary Full Text Full Text PDF PubMed Scopus (162) Google Scholar Considering the high burden of undiagnosed diabetes particularly in Africa,8Price AJ Crampin AC Amberbir A et al.Prevalence of obesity, hypertension, and diabetes, and cascade of care in sub-Saharan Africa: a cross-sectional, population-based study in rural and urban Malawi.Lancet Diabetes Endocrinol. 2018; 6: 208-222Summary Full Text Full Text PDF PubMed Scopus (153) Google Scholar a simplified screening algorithm for patients with diabetes including point-of-care tests using task shifting could potentially address existing health system challenges. Evidence from integrated models of care for chronic conditions in low-resource settings has shown that leveraging of existing human resource, decentralisation of care, task redistribution (including to lay health cadres), and continued training and mentorship are key to successful treatment and control of non-communicable diseases.9Njuguna B Vorkoper S Patel P et al.Models of integration of HIV and noncommunicable disease care in sub-Saharan Africa: lessons learned and evidence gaps.AIDS. 2018; 32: S33-S42Crossref PubMed Scopus (53) Google Scholar, 10Patel P Speight C Maida A et al.Integrating HIV and hypertension management in low-resource settings: lessons from Malawi.PLoS Med. 2018; 15: e1002523Crossref PubMed Scopus (28) Google Scholar An innovative and integrated model of care for diabetes and tuberculosis should therefore be informed by these experiences. Further research is needed to determine the additional cost of adding diabetes screening into the tuberculosis programme along with identifying the most effective approaches for screening and management of diabetes and tuberculosis. Further evidence of the effect of diabetes management and glycemic control on tuberculosis treatment outcome is also required. This data is crucial to inform policy makers to ensure coordinated planning and service delivery of integrated disease programmes. Besides tackling the patients' needs holistically, integration would allow leveraging from successful treatment programmes to tackle emerging chronic conditions like diabetes. We need to fix the whole problem of diabetes, not just among individual patients who have diabetes. Diabetes is one non-communicable disease, but its control alone could easily consume a large portion of health budgets of low-resource countries. The answer has to lie with prevention of the condition; but prevention has to go alongside enhanced treatment services, as we have learnt in HIV. I declare no competing interests. Global prevalence of diabetes in active tuberculosis: a systematic review and meta-analysis of data from 2·3 million patients with tuberculosisThis study suggests a high burden of diabetes among patients with active tuberculosis, with disparities according to age, sex, regions, level of country income, and development. Cost-effective strategies to curb the burden of diabetes among patients with active tuberculosis are needed. Full-Text PDF Open Access