Clinical predictors of pulmonary TB among South African adults with HIV

TB0038

Mendelsohn, S.C., Fiore-Gartland, A., Awany, D., Mulenga, H., Mbandi, S.K., Tameris, M., Walzl, G., Naidoo, K., Churchyard, G., Scriba, T.J. and Hatherill, M., 2022. Clinical predictors of pulmonary tuberculosis among South African adults with HIV. EClinicalMedicine, 45.

CD4 count and antiretroviral initiation are associated with Mtb sensitization and TB disease.

Lower CD4 cell counts are associated with reduced IGRA positivity due to the loss or dysfunction of Mtb-specific T-cell memory responses in HIV.

Clinical prediction models are inadequate for detecting incipient and subclinical TB among people with HIV.

Subclinical TB cases missed by symptom screening may perpetuate Mtb transmission.

There is a need for more sensitive TB screening tools to find “missing” TB cases in high-incidence settings.

Novel active case-finding approaches are needed that do not rely on the presence of symptoms.

Simple clinical prediction models could be used as triage tools in resource-limited settings.

Chest radiography and computer-aided detection offer promise for affordable mass screening and have reasonable performance as a rule-out test for symptomatic individuals with presumptive TB.

 

Diabetes and risk of tuberculosis relapse

Lee, P.H., Lin, H.C., Huang, A.S.E., Wei, S.H., Lai, M.S. and Lin, H.H., 2014. Diabetes and risk of tuberculosis relapse: nationwide nested case-control study. PloS one, 9(3), p.e92623.

Presence of diabetes mellitus (DM) during anti-TB treatment was linked to a higher risk of TB relapse.

The association between DM and TB relapse decreased in individuals older than 60 years.

DM was independently related to an increased risk of TB relapse in the national cohort of TB patients.

Strengthen follow-up strategies for DM-TB patients after anti-TB treatment to detect relapse early.

TB programs should focus on rigorous glucose control for DM-TB patients.

Williams, V., Onwuchekwa, C., Vos, A.G., Grobbee, D.E., Otwombe, K. and Klipstein-Grobusch, K., 2022. Tuberculosis treatment and resulting abnormal blood glucose: a scoping review of studies from 1981-2021. Global Health Action, 15(1), p.2114146.

Diabetes as a Risk Factor for Tuberculosis (TB):

• Numerous studies suggest that diabetes (DM) is a risk factor for TB.
• It remains unclear whether TB or its treatment increases the risk of developing diabetes.
• Impaired glucose tolerance (IGT) may occur during treatment with anti-TB drugs and might resolve after treatment.
• This IGT could result from:
  • Undiagnosed diabetes.
  • A stress response to infection, which increases levels of stress hormones (interleukin-1, interleukin-6, TNF-alpha).
  • Abnormal pancreatic function or TB-induced pancreatitis affecting endocrine function.

Blood Glucose Testing During TB Treatment:

• The Fasting Blood Glucose (FBG) test was the most common method for estimating blood sugar, followed by the Oral Glucose Tolerance Test (OGTT) and HbA1c.
• There was no standardized approach for blood sugar testing; most studies used a combination of methods.
• In studies using multiple tests:
  • HbA1c values were higher.
  • Patients with baseline values in the DM or IGT range were more likely to maintain hyperglycemia throughout treatment.
• HbA1c is useful for identifying long-term glucose abnormalities.
• To better identify DM comorbidity during TB treatment, blood glucose screening timing should be standardized across patients and country programs.
• Some studies only repeated glucose measurements for patients with initial readings in the DM or IGT range, excluding those with normal baseline values.
  • This approach could miss new cases of DM or hyperglycemia during follow-up.
  • It may have been a cost-saving measure or focused on tracking patients with abnormal readings.

Trends in Blood Glucose Levels During TB Treatment:

• Mean blood glucose levels decreased in patients with baseline values in the DM or IGT range who were not previously diagnosed with DM after starting TB treatment.
• The prevalence of elevated blood glucose also decreased during follow-up, consistent with earlier findings that stress hormones in response to the disease may cause initial high blood glucose levels.
• Some patients experienced persistent hyperglycemia after TB treatment, which may be due to:
  • Undiagnosed diabetes before TB infection.
  • Pre-existing IGT, which develops into DM due to additional insulin resistance from infection.

Cavitary Lung Lesions and Hyperglycemia:

• The development of cavitary lung lesions suggests a severe immune response during TB infection and may be associated with hyperglycemia.
• Glucose values typically improve over time with effective TB treatment.
• Good TB treatment outcomes are achievable in DM patients with adequate glucose control.

 

Indoor air pollution from solid fuel and tuberculosis

Lin, H.H., Suk, C.W., Lo, H.L., Huang, R.Y., Enarson, D.A. and Chiang, C.Y., 2014. Indoor air pollution from solid fuel and tuberculosis: a systematic review and meta-analysis. The International journal of tuberculosis and lung disease, 18(5), pp.613-621.

Low Evidence for TB Link: The association between the use of solid fuels in households and tuberculosis (TB) is supported by very low levels of evidence.

Health Risks from Toxic Pollutants: Burning solid fuels can be hazardous, particularly when stoves are inefficient and ventilation is poor, leading to health issues such as acute lower respiratory infections in children under five, chronic obstructive pulmonary disease, and lung cancer.

Factors Affecting Pollutant Levels: The concentration of pollutants from burning solid fuels varies based on the stove type, burning location, and ventilation at the site. These factors help in quantifying pollutant concentrations.

Need for More Research: High-quality studies are required to better understand the relationship between domestic use of solid fuels and TB and to assess the scope of the issue.

-=-

Lai, T.C., Chiang, C.Y., Wu, C.F., Yang, S.L., Liu, D.P., Chan, C.C. and Lin, H.H., 2016. Ambient air pollution and risk of tuberculosis: a cohort study. Occupational and environmental medicine, 73(1), pp.56-61.

Respirable risk factors such as active and passive smoking, and indoor air pollution from biomass, potentially impair airway defense mechanisms, increasing TB risk.

High levels of ambient air pollution in developing countries correlate with continued high tuberculosis rates, necessitating further investigation into its impact on global TB control.

Fine particles and traffic-related pollutants like nitrogen dioxide, nitrogen oxides, and carbon monoxide are linked to a higher risk of active tuberculosis.

Laboratory and ecological studies suggest a positive association between ambient air pollution and TB incidence.

The true relationship between ambient air pollution and TB might be underestimated due to potential residual confounding by area-level socioeconomic factors.

==

Lin, H.H., Murray, M., Cohen, T., Colijn, C. and Ezzati, M., 2008. Effects of smoking and solid-fuel use on COPD, lung cancer, and tuberculosis in China: a time-based, multiple risk factor, modelling study. The Lancet, 372(9648), pp.1473-1483.

Tobacco smoking and indoor air pollution from solid-fuel use are primary global risk factors for chronic obstructive pulmonary disease (COPD) and lung cancer.

These factors significantly contribute to mortality from these diseases in developing countries.

Smoking is an independent risk factor for tuberculosis, exacerbating the spread and severity of the disease.

Implementing moderate to complete reductions in smoking and solid-fuel use through tobacco taxation, advertising bans, and fuel pricing could decrease deaths from COPD and lung cancer.

Reduction in these risk factors would also significantly decrease tuberculosis incidence by minimizing the duration of infectiousness through effective treatment.

These diseases pose substantial economic burdens, particularly in developing countries, due to healthcare costs, reduced labor market participation, and hindered human capital accumulation.

The burden is disproportionately higher in low-income or marginalized communities.

Programs targeting low-income communities could offer cleaner fuels or stoves, nutritional supplements, and tuberculosis testing coupled with treatment adherence incentives.

Tobacco cessation initiatives could be integrated into tuberculosis treatment programs, possibly supported by financial incentives.

Revenue from tobacco taxes could subsidize Directly Observed Treatment, Short-course (DOTS), clean energy technologies, and nutrition programs for participating low-income households.

 

Feasibility of achieving the 2025 WHO global tuberculosis targets in South Africa, China, and India

Houben, R.M., Menzies, N.A., Sumner, T., Huynh, G.H., Arinaminpathy, N., Goldhaber-Fiebert, J.D., Lin, H.H., Wu, C.Y., Mandal, S., Pandey, S. and Suen, S.C., 2016. Feasibility of achieving the 2025 WHO global tuberculosis targets in South Africa, China, and India: a combined analysis of 11 mathematical models. The Lancet Global Health, 4(11), pp.e806-e815.

Aggressive scaling of a single intervention is not enough to meet the post-2015 End TB Strategy targets globally.

In South Africa:

• A combination of targeted interventions could substantially reduce tuberculosis:
  • Continuous isoniazid preventive therapy for individuals on antiretroviral therapy.
  • Expanded facility-based screening for tuberculosis symptoms at health centers.
  • Enhanced tuberculosis care.
• Using these interventions, significant reductions in tuberculosis are feasible, and meeting the 2025 targets is possible.

For other high-burden countries like China and India, additional country-specific interventions are required:

• In China, addressing latent tuberculosis in the elderly.
• In India, combating undernutrition to help reach the global tuberculosis targets.

  

Enhanced DM management reduce the risk and improve the outcome of TB

Lo, H.Y., Yang, S.L., Lin, H.H., Bai, K.J., Lee, J.J., Lee, T.I. and Chiang, C.Y., 2016. Does enhanced diabetes management reduce the risk and improve the outcome of tuberculosis?. The International Journal of Tuberculosis and Lung Disease, 20(3), pp.376-382.

Diabetic TB patients face higher risks of treatment failure, death, and recurrent TB compared to non-diabetic TB patients.

Patients with diabetes mellitus (DM) enrolled in an enhanced case management program for DM had a lower likelihood of developing TB.

If they developed TB, patients in the enhanced DM management program experienced better outcomes than those not enrolled in the program.

 -=-

In low and moderate TB incidence countries, TB often concentrates in specific groups, notably those with diabetes. In Taiwan, diabetes mellitus (DM) is the leading risk factor for pulmonary TB. After adjusting for confounders, type 2 DM is an independent risk factor for TB nationwide, though the association is stronger for type 1 DM. Poor glycemic control can increase the hazard ratio for TB in adults under 65, with men and individuals aged 55–64 at greater risk. TB patients with heart failure, ischemic heart disease, stroke, hypertension, dyslipidemia, chronic kidney disease, and liver disease are more likely to have DM.

Interestingly, obesity does not increase TB risk despite its link to diabetes. TB incidence and mortality have decreased in Taiwan, yet DM remains the fifth leading cause of death. In newly diagnosed TB patients, those with DM experience higher mortality rates. Proper TB treatment has been shown to improve glycemic control, possibly due to TB-induced hyperglycemia through stress dysglycemia mechanisms. Both anti-TB and antidiabetic treatments may help mitigate hyperglycemia.

Chronic hyperglycemia impairs immunity to M. tuberculosis and affects lung perfusion, reducing immune response in diabetic patients. Those with poor glycemic control (fasting plasma glucose >130 mg/dL) have a higher TB hazard, while those with good control (FPG <130 mg/dL) do not significantly differ from non-diabetics. Diabetics with HbA1c >7% are more likely to be smear-positive for TB compared to those with HbA1c <7%.

Initial two-year metformin (MET) use reduces active TB risk, with a greater effect at higher dosages. MET also reduces DM-related mortality during TB treatment. Ezetimibe, a cholesterol-lowering drug, shows promise as adjunctive therapy for TB by lowering latent TB prevalence, intracellular lipid content, and M. tuberculosis growth in leukocytes among diabetic patients. While DM significantly raises the odds of multidrug-resistant TB (MDR-TB), the impact of glycemic control on MDR-TB outcomes remains unclear.

Source: Wang, M.C. and Cervantes, J., 2019. Glycemic control in tuberculosis: lessons learned from Taiwan. Asian Pacific Journal of Tropical Medicine, 12(10), pp.438-441. https://journals.lww.com/aptm/fulltext/2019/12100/glycemic_control_in_tuberculosis__lessons_learned.2.aspx