Association of diabetes, smoking, and alcohol use with subclinical-to-symptomatic spectrum of tuberculosis in 16 countries: an individual participant data meta-analysis of national tuberculosis prevalence surveys

Background

Non-communicable diseases (NCDs) and NCD risk factors, such as smoking, increase the risk for tuberculosis (TB). Data are scarce on the risk of prevalent TB associated with these factors in the context of population-wide systematic screening and on the association between NCDs and NCD risk factors with different manifestations of TB, where ∼50% being asymptomatic but bacteriologically positive (subclinical). We did an individual participant data (IPD) meta-analysis of national and sub-national TB prevalence surveys to synthesise the evidence on the risk of symptomatic and subclinical TB in people with NCDs or risk factors, which could help countries to plan screening activities.

Methods

In this systematic review and IPD meta-analysis, we identified eligible prevalence surveys in low-income and middle-income countries that reported at least one NCD (e.g., diabetes) or NCD risk factor (e.g., smoking, alcohol use) through the archive maintained by the World Health Organization and by searching in Medline and Embase from January 1, 2000 to August 10, 2021. The search was updated on March 23, 2023. We performed a one-stage meta-analysis using multivariable multinomial models. We estimated the proportion of and the odds ratio for subclinical and symptomatic TB compared to people without TB for current smoking, alcohol use, and self-reported diabetes, adjusted for age and gender. Subclinical TB was defined as microbiologically confirmed TB without symptoms of current cough, fever, night sweats, or weight loss and symptomatic TB with at least one of these symptoms. We assessed heterogeneity using forest plots and I2 statistic. Missing variables were imputed through multi-level multiple imputation. This study is registered with PROSPERO (CRD42021272679).

Findings

We obtained IPD from 16 national surveys out of 21 national and five sub-national surveys identified (five in Asia and 11 in Africa, N = 740,815). Across surveys, 15.1%-56.7% of TB were subclinical (median: 38.1%). In the multivariable model, current smoking was associated with both subclinical (OR 1.67, 95% CI 1.27-2.40) and symptomatic TB (OR 1.49, 95% CI 1.34-1.66). Self-reported diabetes was associated with symptomatic TB (OR 1.67, 95% CI 1.17-2.40) but not with subclinical TB (OR 0.92, 95% CI 0.55-1.55). For alcohol drinking ≥ twice per week vs no alcohol drinking, the estimates were imprecise (OR 1.59, 95% CI 0.70-3.62) for subclinical TB and OR 1.43, 95% CI 0.59-3.46 for symptomatic TB). For the association between current smoking and symptomatic TB, I2 was high (76.5% (95% CI 62.0-85.4), while the direction of the point estimates was consistent except for three surveys with wide CIs.

Interpretation

Our findings suggest that current smokers are more likely to have both symptomatic and subclinical TB. These individuals can, therefore, be prioritised for intensified screening, such as the use of chest X-ray in the context of community-based screening. People with self-reported diabetes are also more likely to have symptomatic TB, but the association is unclear for subclinical TB.

Funding

None.

Serological Surveys for complementing assessments of vaccination coverage in sub-Saharan Africa: A systematic review

Background: Serosurveys of biomarkers of infection/vaccination are widely used for evaluating vaccine-induced immunity and monitoring the effectiveness of immunisation programmes in developed countries. In sub-Saharan Africa (sSA) where vaccination coverage (VC) estimates are often incomplete, inaccurate and overestimate effective population immunity, the use of serosurveys is limited. Methods: We conducted a review of the use of serosurveys to assess/complement assessments of VC in sSA by searching electronic databases (PubMed, Embase, Web of Science, Popline, Ovid and Africa Wide Information) for English language articles published from 1st January 1940 to 31st January 2017. We also searched the references of retrieved articles. SSA was defined as all of Africa excluding the countries in North Africa. We included only articles that measured VC and assessed the quality of these studies using the Newcastle-Ottawa Scale. Results: We found 1056 unique records, reviewed 20 eligible studies of which just 12 met our inclusion criteria. These 12 studies were serosurveys of measles, tetanus, polio and yellow fever. Antibodies induced by natural infection confounded serological test results and there was significant discordance between vaccination history and the presence of antibodies in all except for tetanus vaccine. No study looked at Hepatitis B. Conclusions: Serosurveys for tetanus or tetanus containing vaccines may be directly useful for ascertainment of vaccination exposure or reliably complement current survey methods that measure VC. Given the limited experience in using serosurveys for this purpose in sSA, well-designed serosurveys of tetanus and possibly hepatitis B are required to further validate/evaluate their performance.

Crude childhood vaccination coverage in West Africa: Trends and predictors of completeness

Background: Africa has the lowest childhood vaccination coverage worldwide. If the full benefits of childhood vaccination programmes are to be enjoyed in sub-Saharan Africa, all countries need to improve on vaccine delivery to achieve and sustain high coverage. In this paper, we review trends in vaccination coverage, dropouts between vaccine doses and explored the country-specific predictors of complete vaccination in West Africa.  Methods: We utilized datasets from the Demographic and Health Surveys Program, available for Benin, Burkina Faso, The Gambia, Ghana, Guinea, Cote d'Ivoire, Liberia, Mali, Niger, Nigeria, Senegal, Sierra Leone and Togo, to obtain coverage for Bacillus Calmette-Guerin, polio, measles, and diphtheria, pertussis and tetanus (DPT) vaccines in children aged 12 - 23 months. We also calculated the DPT1-to-DPT3 and DPT1-to-measles dropouts, and proportions of the fully immunised child (FIC). Factors predictive of FIC were explored using Chi-squared tests and multivariable logistic regression.  Results: Overall, there was a trend of increasing vaccination coverage. The proportion of FIC varied significantly by country (range 24.1-81.4%, mean 49%). DPT1-to-DPT3 dropout was high (range 5.1% -33.9%, mean 16.3%). Similarly, DPT1-measles dropout exceeded 10% in all but four countries. Although no single risk factor was consistently associated with FIC across these countries, maternal education, delivery in a health facility, possessing a vaccine card and a recent post delivery visit to a health facility were the key predictors of complete vaccination.  Conclusions: The low numbers of fully immunised children and high dropout between vaccine doses highlights weaknesses and the need to strengthen the healthcare and routine immunization delivery systems in this region. Country-specific correlates of complete vaccination should be explored further to identify interventions required to increase vaccination coverage. Despite the promise of an increasing trend in vaccination coverage in West African countries, more effort is required to attain and maintain global vaccination coverage targets.

Differential transcriptomic and metabolic profiles of M. africanum- and M. tuberculosis-infected patients after, but not before, drug treatment

The epidemiology of Mycobacterium tuberculosis (Mtb) and M. africanum (Maf) suggest differences in their virulence, but the host immune profile to better understand the pathogenesis of tuberculosis (TB) have not been studied. We compared the transcriptomic and metabolic profiles between Mtb and Maf-infected TB cases to identify host biomarkers associated with lineages-specific pathogenesis and response to anti-TB chemotherapy. Venous blood samples from Mtb- and Maf-infected patients obtained before and after anti-TB treatment were analysed for cell composition, gene expression and metabolic profiles. Prior to treatment, similar transcriptomic profiles were seen in Maf- and Mtb-infected patients. In contrast, post-treatment, over 1600 genes related to immune responses and metabolic diseases were differentially expressed between the groups. Notably, the upstream regulator hepatocyte nuclear factor 4-alpha (HNF4α), which regulated 15% of these genes, was markedly enriched. Serum metabolic profiles were similar in both group pre-treatment, but the decline in pro-inflammatory metabolites post-treatment were most pronounced in Mtb-infected patients. Together, the differences in both peripheral blood transcriptomic and serum metabolic profiles between Maf- and Mtb-infected patients observed over the treatment period, might be indicative of intrinsic host factors related to susceptibility to TB and/or differential efficacy of the standard anti-TB treatment on the two lineages.

Spatial analysis of tuberculosis in an urban west African setting: is there evidence of clustering?

OBJECTIVES

To describe the pattern of tuberculosis (TB) occurrence in Greater Banjul, The Gambia with Geographical Information Systems (GIS) and Spatial Scan Statistics (SaTScan) and to determine whether there is significant TB case clustering.

METHODS

In Greater Banjul, where 80% of all Gambian TB cases arise, all patients with TB registered at chest clinics between March 2007 and February 2008 were asked to participate. Demographic, clinical characteristics and GPS co-ordinates for the residence of each consenting TB case were recorded. A spatial scan statistic was used to identify purely spatial and space-time clusters of tuberculosis among permanent residents.

RESULTS

Of 1145 recruited patients with TB, 84% were permanent residents with 88% living in 37 settlements that had complete maps available down to settlement level. Significant high- and low-rate spatial and space-time clusters were identified in two districts. The most likely cluster of high rate from both the purely spatial analysis and the retrospective space-time analysis were from the same geographical area. A significant secondary cluster was also identified in one of the densely populated areas of the study region.

CONCLUSIONS

There is evidence of significant clustering of TB cases in Greater Banjul, The Gambia. Systematic use of cluster detection techniques for regular TB surveillance in The Gambia may aid effective deployment of resources. However, passive case detection dictates that community-based active case detection and risk factor surveys would help confirm the presence of true clusters and their causes.