Diabetes Mellitus–Tuberculosis Comorbidity in Low–Resource Settings
Authors:   , Williams Victor Murphy 
Published: March 2024

Introduction
Despite being known for more than two centuries and with effective treatment, several people continue to die from diabetes mellitus and tuberculosis annually. Current estimates show that low-resource settings, particularly Sub-Saharan Africa, have the highest incidence of new tuberculosis cases, with a year-on-year increase in diabetes mellitus cases. Furthermore, diabetes mellitus is associated with tuberculosis. People with diabetes mellitus are more likely to develop tuberculosis disease with unfavourable treatment outcomes and relapse after tuberculosis treatment. While the high tuberculosis incidence in low-resource settings could be attributed to immunosuppression from HIV, undernourishment, overcrowding and poor housing infrastructure, the rise in diabetes mellitus is attributed to physical inactivity, unhealthy diet, poor glycaemic control, overweight and obesity. Estimates indicate the cases of diabetes mellitus will increase in the coming years. This will increase the burden of care for diabetes while increasing the risks for tuberculosis control amid limited health infrastructure and funding. To understand diabetes mellitus–tuberculosis comorbidity in a high HIV-prevalent setting, this thesis describes the epidemiology of diabetes mellitus–tuberculosis in a low-resource setting, the effect of blood glucose on TB treatment outcomes, the opportunities to improve tuberculosis management practices, the impact of COVID-19 on tuberculosis services and recommendations to improve integrated care for diabetes mellitus and tuberculosis.

Methods
This thesis used a mixed-methods study design consisting of a qualitative interview of 23 healthcare workers who provide tuberculosis services and a prospective cohort study of 369 patients commencing tuberculosis treatment at 11 health facilities from the four regions of Eswatini. The healthcare workers' interview described the integration and access to diabetes mellitus-tuberculosis services by patients, opportunities for improved diabetes mellitus-tuberculosis service provision and the impact of the COVID-19 pandemic on tuberculosis services while the prospective cohort study described the epidemiology of diabetes mellitus-tuberculosis comorbidity, the effect of blood glucose on tuberculosis treatment outcomes and tuberculosis treatment outcomes.

Results
Although the healthcare workers indicated diabetes mellitus–tuberculosis services were integrated, the implementation was hindered by some challenges, including staff shortages, limited knowledge of care for TB patients with comorbid conditions, frequent stockouts of laboratory commodities for screening and monitoring of clients for diabetes and tuberculosis, and frequent stock out of drugs for the treatment of diabetes and tuberculosis. The COVID-19 pandemic impacted all aspects of healthcare delivery, and healthcare workers adopted different approaches, such as home-based care and community outreaches, to provide care. While 8% of the patients had elevated blood glucose, elevated blood glucose was not associated with unfavourable tuberculosis treatment outcomes, and three-quarters had a favourable treatment outcome. Death was the most common unfavourable treatment outcome, and HIV was not associated with an unfavourable treatment outcome.

Conclusion
Health system challenges hinder the effective integration of diabetes mellitus–tuberculosis services. Given the annual increases in diabetes mellitus cases in the presence of a high tuberculosis burden, an overall improvement in health system infrastructures is necessary for improved diabetes mellitus–tuberculosis services. Additional study is required to identify alternative causes of death in patients receiving tuberculosis treatment apart from HIV.