Quantifying progression and regression across the spectrum of pulmonary tuberculosis: a data synthesis study

Post-tuberculosis lung disease: towards prevention, diagnosis, and care

There is a growing body of data describing the high burden of respiratory sequelae seen among tuberculosis survivors, including children, adolescents, and adults. This group of sequelae are known as post-tuberculosis lung disease and include parenchymal damage, airway disease, and pulmonary vascular disease. It is thought that approximately half of pulmonary tuberculosis survivors have ongoing structural pathology, lung function impairment, or respiratory symptoms after the resolution of active disease. Post-tuberculosis lung disease has been associated with adverse patient outcomes, including persistent symptoms and functional impairment, ongoing health seeking, and impacts on income and employment. There is still much to understand about the epidemiology and nature of post-tuberculosis lung disease, but in this Review we focus on strategies for prevention, diagnosis, and care to inform the ongoing work of tuberculosis-affected communities, health-care providers, researchers, and policy makers. We summarise recent data, highlight evidence gaps, and suggest key research priorities for those working in the field.

Prominence of Mycobacterium tuberculosis biomarkers among sputum culture-negative clinic attendees, independent of Ultra status

BACKGROUND

Highly-sensitive molecular tests like GeneXpert MTB/RIF Ultra improve detection of paucibacillary pulmonary tuberculosis (TB) but occasionally detect Mycobacterium tuberculosis (Mtb) DNA in sputum from culture-negative individuals, with unclear significance. We hypothesized that Ultra may be detecting culture-negative TB, and manifest in a higher prevalence of TB biomarkers compared to Ultra-negative/culture-negative ('sputum-negative') individuals.

METHODS

From 1200 symptomatic African adults undergoing evaluation for TB, we identified 66 with discordant results (Ultra-positive, culture-negative), and matched 52 sputum-negative (Ultra-negative, culture-negative) and 30 sputum-positive (Ultra-positive, culture-positive) participants. Over 12 months, participants were assessed for Mtb biomarkers (Mtb growth in augmented or follow-up sputum cultures, Mtb mRNA in baseline sputum, and symptomatic Ultra-positive after baseline) and TB-associated host transcriptional signatures.

RESULTS

At baseline, TB-associated biomarker(s) were detected in 51.5 % of sputum-discordant versus 59.6 % of sputum-negative participants (p = 0.46), with at least one Mtb biomarker in 16.7 % versus 26.9 % respectively (p = 0.26). Longitudinally, 26.5 % of untreated sputum-discordant versus 41.7 % of untreated sputum-negative participants had Mtb biomarkers (p = 0.17) despite most reporting symptom improvement. Notably, 30 % of untreated sputum-negative participants converted to Ultra-positive at month 2. One sputum-discordant and one sputum-negative participant developed culture-confirmed TB at follow-up.

CONCLUSION

TB bacterial and host biomarkers were prevalent and no different between sputum-discordant and sputum-negative participants, raising concern for a considerable population of undiagnosed culture-negative TB. These findings parallel new evidence of Mtb aerosolization from sputum-negative individuals and highlight a need for more comprehensive diagnostics that detect sputum culture-negative TB with respect to infectiousness, pathology, and risk of progression.

Tuberculosis disease severity assessment using clinical variables and radiology enabled by artificial intelligence

Radiology can define tuberculosis (TB) severity and may guide duration of treatment, however the optimal radiological metric to use and which clinical variables to combine it with in the real-world is unclear. We systematically associated baseline chest X-rays (CXR) metrics with TB treatment outcome using real-world data from diverse TB clinical settings. We used logistic regression to associate 10 radiological metrics including percent of lung involved in disease (PLI), cavitation, and Timika score, alone or with other clinical characteristics, stratifying by drug resistance and HIV (n = 2,809). We fine-tuned convolutional neural nets (CNN) to automate PLI measurement from the CXR DICOM images (n = 5,261). PLI is the only CXR finding associated with unfavorable outcome across drug resistance and HIV subgroups [rifampicin-susceptible disease without HIV, adjusted odds ratio 1·11 (1·01, 1·22), P-value 0·025]. The most informed model of baseline characteristics tested predicts outcome with a validation mean area under the curve (AUC) of 0·769. PLI alone predicts unfavorable outcomes equally or better than Timika or cavitary information (AUC PLI 0·656 vs. Timika 0·655 and cavitation best 0·591). PLI>25% provides a better separation of favorable and unfavorable outcomes compared to PLI>50% currently used in some clinical trials. The best performing ensemble of CNNs has an AUC 0·850 for PLI>25% and mean absolute error of 11·7% for the PLI value. PLI is better than cavitation, is accurately predicted with CNNs, and is optimally combined with age, sex, and smear grade for predicting unfavorable treatment outcome in pulmonary TB in real-world settings.

Significance Statement

A systematic evaluation of specific CXR findings in combination with clinical variables and their association with unfavorable outcomes in real-world settings is currently lacking. Stratification by severity of pulmonary TB can support personalized treatment, including the identification of patient groups that can be cured reliably with a shortened treatment regimen. Shorter regimens can minimize drug side effects, improve adherence and reduce costs of care. With the wider use of digital CXR and the increased adoption of AI for computer assisted diagnosis, radiology has the potential to be leveraged for multiple uses in the treatment and monitoring of TB disease, including contributing to a more individualized approach to TB treatment.

The long-term risk of tuberculosis among individuals with Xpert Ultra "trace" screening results: a longitudinal follow-up study

Background

Systematic screening for tuberculosis using Xpert Ultra generates "trace" results of uncertain significance. Additional microbiological testing in this context is often negative, but individuals with trace results might have early disease or elevated risk of tuberculosis.

Methods

We screened for tuberculosis with Xpert Ultra in Uganda, enrolling individuals with trace-positive results and Ultra-negative controls. Participants without tuberculosis on extensive initial evaluation were followed, with repeat testing at 1, 3, and 6 months after trace results, and at 12 and 24 months for all participants. We estimated cumulative cause-specific hazards of incident tuberculosis, considering a definition of tuberculosis that included clinician judgment and one based strictly on microbiological results. We compared participants with Ultra-trace versus Ultra-negative sputum, and subgroups of participants with Ultra-trace sputum.

Findings

Of 129 participants with trace-positive screening results, 45 (35%) were recommended for treatment upon enrollment, and eight were lost to follow-up within three months. Of 76 remaining participants followed for median 697 (interquartile range 179-714) days, 20 (26%) were recommended for tuberculosis treatment. The cumulative hazard of clinician-defined incident tuberculosis was 26% (95% confidence interval: 14-38%) at one year and 35% (19-52%) at two years, versus 2% (0-5%) at two years for controls. Hazards were similar for microbiologically defined incident tuberculosis. Incident tuberculosis was strongly associated with abnormal baseline chest X-ray (hazard ratio 15.0 [3.4-65.1]) but not with baseline symptoms.

Interpretation

Individuals with trace-positive sputum during screening, particularly those with abnormal chest imaging, are at substantial risk of incident tuberculosis over the subsequent two years.

Funding

National Institutes of Health.

Tuberculosis and HIV coinfection: Progress and challenges towards reducing incidence and mortality

HIV-associated tuberculosis (HIV-TB) is associated with disproportionate mortality: approximately 24% of the 660,000 individuals with TB and HIV died, compared to 11% of those without HIV dying from TB in 2023. HIV is a key driver of ongoing high TB incidence in many countries, particularly in the World Health Organization Africa region, and TB is the leading cause of hospitalization in people with HIV (PWH) globally. Significant developments have occurred recently concerning the prevention, screening, diagnosis, and management of HIV-TB. Antiretroviral therapy and novel regimens for TB preventive therapy are now known to decrease TB incidence and improve survival. The use of Xpert Ultra (Cepheid, USA) and urine DetermineTM TB LAM Antigen (Abbott, USA) as diagnostics are associated with improved survival for HIV-TB. However, there are ongoing gaps in our knowledge: regarding the natural history of TB disease in PWH; optimal approaches to diagnosis of TB and TB drug resistance including in non-sputum samples; and post-TB disease in PWH. We discuss recent progress, together with ongoing challenges towards reducing incidence, morbidity, and mortality. We highlight ongoing research that will advance our understanding and management of HIV-TB: including vaccine research, novel treatment strategies, and expanded options for the diagnosis of TB and drug resistance in PWH.

Screening for Asymptomatic Tuberculosis among Adults with Household Exposure to a Patient with Pulmonary Tuberculosis

Background

More than half of tuberculosis (TB) detected by community prevalence surveys is classified as asymptomatic. We evaluated yield of symptom and chest radiograph (CXR) screening of TB-exposed household contacts (HHC) in South Africa.

Methods

Adult volunteers (≥18 years) with household exposure to pulmonary TB patients were enrolled at three sites. Systematic screening of TB symptoms (any duration), CXR (any abnormality), and sputum microscopy, Xpert Ultra, and liquid culture were performed. Serum C-reactive protein (CRP) was measured by multiplex bead array. Prevalent TB was microbiologically-confirmed (Xpert Ultra or culture). Symptomatic and asymptomatic TB were defined as prevalent TB with and without reported symptoms, respectively.

Results

Between March 2021 - December 2022, 979 HHC were enrolled; 185 (18.9%) living with HIV and 187 (19.1%) with previous TB. Prevalent TB occurred in 51 (5.2%) and was asymptomatic in 42/51 (82.4%). Only 13/42 (31.0%) asymptomatic TB cases were smear-positive [8/13 (61.5%) graded scanty or 1+]. CRP did not discriminate healthy HHC from those with asymptomatic TB (AUC 0.60; 95%CI 0.47-0.73). An abnormal CXR was observed in 23/41 asymptomatic (sensitivity 56.1%, 95%CI 41.0-70.1%) versus 8/9 symptomatic (sensitivity 88.9%, 95%CI 56.5-98.0%) TB cases. Sensitivity of CXR in combination with symptom screening was 64.0% (32/50, 95%CI 50.1-75.9%) for all prevalent TB.

Conclusions

More than 80% of confirmed TB cases among HHC were asymptomatic. CXR screening missed more than 40% of these asymptomatic cases. Community prevalence surveys reliant on symptom- and CXR-based approaches may significantly underestimate the prevalence of asymptomatic TB in endemic countries.

Funding

Supported by RePORT South Africa through funding from the U.S. National Institutes of Health, CRDF Global, and the South African Medical Research Council.

RESEARCH IN CONTEXT

Evidence before this study: World Health Organisation (WHO) guidelines for systematic tuberculosis (TB) screening recommend symptom screening and chest radiography (CXR), based on a Cochrane meta-analysis reporting 70.6% sensitivity (any TB symptom) and 94.7% sensitivity (any CXR abnormality) for bacteriologically-confirmed pulmonary TB. National TB prevalence surveys rely on a positive symptom screen or abnormal CXR to trigger diagnostic sputum testing. This approach to community screening would, by definition, miss asymptomatic TB cases without CXR evidence of disease. We reviewed the reference list of the aforementioned meta-analysis for active case-finding studies of adolescents and adults aged 15 years and older in community and contact-tracing settings. We performed forward citation-tracking and searched reference lists, including studies published in English between Jan 1, 1980, and November 1, 2024. We excluded studies that included children <15 years; or that exclusively enrolled people with additional risk factors (HIV; diabetes; latent TB infection; prior TB). We found 28 studies that performed universal sputum testing for bacteriologically-confirmed pulmonary TB and reported 51.8% (95%CI 49.9-53.7%; I 2 = 89.2%) pooled sensitivity for symptom screening (any symptom; 24 studies, 2,969 TB cases) and 62.4% (95%CI 59.3-65.3%; I 2 = 88.3%) pooled sensitivity for CXR (any abnormality; 10 studies, 1,123 TB cases). Only four studies (145 TB cases) reported accuracy of symptom screening in parallel with chest radiography (pooled sensitivity 67.3%, 95%CI 57.3-75.9%; I 2 = 87.1%), but these studies did not disaggregate symptomatic and asymptomatic disease. Added value of this study: We performed systematic screening using universal sputum microbiological testing of 978 household contacts of pulmonary TB patients in three South African communities and compared symptom (any duration) and CXR (any abnormality) screening approaches against a microbiological reference standard. We detected confirmed pulmonary TB in 5.2% of household contacts, and 82.4% of these TB cases reported no TB symptoms. Asymptomatic TB in household contacts was pauci-bacillary and associated with low serum CRP levels that were indistinguishable from healthy controls, but distinct from symptomatic TB in a comparator group of clinic attendees. Sensitivity of CXR screening for asymptomatic TB was only 56.1%; sensitivity of combined symptom and CXR screening for all TB was marginally higher at 64.0%.Implications of all the available evidence: Our findings from household contacts suggest that symptom- and CXR-based approaches are inadequate for community TB screening in South Africa and do not meet the WHO Target Product Profile for a TB screening test (minimum 90% sensitivity; 70% specificity). National TB Prevalence Surveys that omit universal sputum microbiological testing may significantly underestimate the prevalence of asymptomatic TB in high-burden countries.

Incipient and subclinical tuberculosis: a narrative review

Mycobacterium tuberculosis has been known to infect humans for eons. It is an airborne infectious disease transmitted through droplet nuclei of 1 to 5 µm in diameter. Historically, tuberculosis (TB) was considered a distinct condition characterized by TB infection and active TB disease. However, recently, the concept of a dynamic spectrum of infection has emerged, wherein the pathogen is initially eradicated by the innate or adaptive immune system, either in conjunction with or independently of T cell priming. Other categories within this spectrum include TB infection, incipient TB, subclinical TB, and active TB disease. Various host- and pathogen-related factors influence these categories. Furthermore, subclinical TB can facilitate the spread of infection within the community. Due to its asymptomatic nature, there is a risk of delayed diagnosis, and some patients may remain undiagnosed. Individuals with subclinical TB may stay in this stage for an indeterminate period without progressing to active TB disease, and some may even experience regression. Early diagnosis and treatment of TB are essential to meet the 2035 targets outlined in the end-TB strategy. This strategy should also include incipient and subclinical TB. This review will focus on the definition, natural history, burden, trajectory, transmissibility, detection, and management of early-stage TB.

Altered IL-6 signalling and risk of tuberculosis: a multi-ancestry mendelian randomisation study

BACKGROUND

The role of IL-6 responses in human tuberculosis risk is unknown. IL-6 signalling inhibitors, such as tocilizumab, are thought to increase the risk of progression to tuberculosis, and screening for latent Mycobacterium tuberculosis infection before using these drugs is widely recommended. We used single nucleotide polymorphisms (SNPs) in and near the IL-6 receptor gene (IL6R), including the non-synonymous variant, rs2228145, for which the C allele contributes to reduced classic (cis) IL-6 signalling activity, to test the hypothesis that altered IL-6 signalling is causally associated with the risk of developing tuberculosis.

METHODS

We performed a meta-analysis of genome-wide association studies (GWAS) published in English from database inception to Jan 1, 2024. GWAS were identified from the European Bioinformatics Institute, MRC Integrative Epidemiology Unit catalogues, and MEDLINE, selecting publicly available studies for which tuberculosis was an outcome and that included the IL6R rs2228145 SNP. Using each study's population-level summary statistics, effect estimates were extracted for each additional copy of the C allele of rs2228145. We used these estimates to perform multi-ancestry, two-sample mendelian randomisation analyses to estimate the causal effect of reduced IL-6 signalling on tuberculosis. Our primary analyses used rs2228145-C as a genetic instrument, weighted on C-reactive protein (CRP) reduction as a measure of the effect on IL-6 signalling. We also took an alternative, ancestry-specific, multiple SNP approach using IL-6 receptor plasma protein as an exposure. Additionally, we compared the effects of rs2228145 in tuberculosis with those in critical COVID-19, rheumatoid arthritis, Crohn's disease, and coronary artery disease using the summary statistics extracted from GWAS.

FINDINGS

17 GWAS were included, collating data for 19 302 individuals with tuberculosis (cases) and 1 019 821 population controls across multiple ancestries. For each additional rs2228145-C allele, the odds of tuberculosis reduced (odds ratio [OR] 0·94 [95% CI 0·92-0·97]; p=6·8 × 10-6). Multi-ancestry mendelian randomisation analyses supported these findings, with decreased odds of tuberculosis associated with readouts of reduced IL-6 signalling (0·52 [0·39-0·69] for each natural log CRP decrease; p=6·8 × 10-6), with weak evidence of heterogeneity (I2=0·315; p=0·11). Ancestry-specific, multiple SNP mendelian randomisation using increase in IL-6 receptor plasma protein as an exposure revealed a similar reduced risk of tuberculosis (OR 0·94 [95% CI 0·93-0·96]; p=2·4 × 10-10). The protective effects on tuberculosis seen with rs2228145-C were similar in size and direction to those observed in critical COVID-19 (0·66 [0·50-0·86]), Crohn's disease (0·57 [0·44-0·74]), and rheumatoid arthritis (0·45 [0·36-0·58]), all of which benefit from the therapeutic effects of IL-6 antagonism.

INTERPRETATION

Our findings propose a causal relationship between reduced IL-6 signalling and lower risk of tuberculosis, akin to the effect seen in other IL-6 mediated diseases. This study suggests that IL-6 antagonists do not increase the risk of tuberculosis but rather should be investigated as therapeutic adjuncts in its treatment.

FUNDING

UK National Institute for Health and Care Research, Wellcome Trust, EU European Regional Development Fund, the Welsh Government, and UK Research and Innovation.

Estimating the Impact of Tuberculosis Pathways on Transmission-What Is the Gap Left by Passive Case Finding?

Current passive case-finding policies have not resulted in the expected decline in tuberculosis incidence. Recognition of the variety of disease pathways experienced by individuals with tuberculosis highlights how many are not served by the current prevention and care system and how much transmission is missed.

Implications of subclinical tuberculosis for vaccine trial design and global effect

Tuberculosis is a leading cause of death from an infectious agent globally. Infectious subclinical tuberculosis accounts for almost half of all tuberculosis cases in national tuberculosis prevalence surveys, and possibly contributes to transmission and might be associated with morbidity. Modelling studies suggest that new tuberculosis vaccines could have substantial health and economic effects, partly based on the assumptions made regarding subclinical tuberculosis. Evaluating the efficacy of prevention of disease tuberculosis vaccines intended for preventing both clinical and subclinical tuberculosis is a priority. Incorporation of subclinical tuberculosis as a composite endpoint in tuberculosis vaccine trials can help to reduce the sample size and duration of follow-up and to evaluate the efficacy of tuberculosis vaccines in preventing clinical and subclinical tuberculosis. Several design options with various benefits, limitations, and ethical considerations are possible in this regard, which would allow for the generation of the evidence needed to estimate the positive global effects of tuberculosis vaccine trials, in addition to informing policy and vaccination strategies.

Active case finding to detect symptomatic and subclinical pulmonary tuberculosis disease: implementation of computer-aided detection for chest radiography in Viet Nam

Objective

In Viet Nam, tuberculosis (TB) prevalence surveys revealed that approximately 98% of individuals with pulmonary TB have TB-presumptive abnormalities on chest radiographs, while 32% have no TB symptoms. This prompted the adoption of the "Double X" strategy, which combines chest radiographs and computer-aided detection with GeneXpert testing to screen for and diagnose TB among vulnerable populations. The aim of this study was to describe demographic, clinical and radiographic characteristics of symptomatic and asymptomatic Double X participants and to assess multilabel radiographic abnormalities on chest radiographs, interpreted by computer-aided detection software, as a possible tool for detecting TB-presumptive abnormalities, particularly for subclinical TB.

Methods

Double X participants with TB-presumptive chest radiographs and/or TB symptoms and known risks were referred for confirmatory GeneXpert testing. The demographic and clinical characteristics of all Double X participants and the subset with confirmed TB were summarized. Univariate and multivariable logistic regression modelling was used to evaluate associations between participant characteristics and subclinical TB and between computer-aided detection multilabel radiographic abnormalities and TB.

Results

From 2020 to 2022, 96 631 participants received chest radiographs, with 67 881 (70.2%) reporting no TB symptoms. Among 1144 individuals with Xpert-confirmed TB, 51.0% were subclinical. Subclinical TB prevalence was higher in older age groups, non-smokers, those previously treated for TB and the northern region. Among 11 computer-aided detection multilabel radiographic abnormalities, fibrosis was associated with higher odds of subclinical TB.

Discussion

In Viet Nam, Double X community case finding detected pulmonary TB, including subclinical TB. Computer-aided detection software may have the potential to identify subclinical TB on chest radiographs by classifying multilabel radiographic abnormalities, but further research is needed.

Persistent Mycobacterium tuberculosis bioaerosol release in a tuberculosis-endemic setting

Pioneering studies linking symptomatic disease and cough-mediated Mycobacterium tuberculosis (Mtb) release established the infectious origin of tuberculosis (TB), simultaneously informing the notion that pathology is a prerequisite for Mtb transmission. Our recent work has challenged this assumption: by sampling TB clinic attendees, we detected equivalent release of Mtb-containing bioaerosols by confirmed TB patients and individuals not receiving a TB diagnosis and observed time-dependent reduction in Mtb bioaerosol positivity during 6-month follow-up of both cohorts, irrespective of anti-TB chemotherapy. Now, we report widespread Mtb release in our TB-endemic setting: of 89 randomly recruited community members, 79.8% (71/89) produced Mtb-containing bioaerosols independently of QuantiFERON status, a standard test for Mtb exposure. Moreover, during 2-month longitudinal sampling, only 2% (1/50) were serially Mtb bioaerosol negative. These results necessitate a reframing of the prevailing paradigm of Mtb transmission and TB etiology, perhaps explaining the historical inability to elucidate Mtb transmission networks in TB-endemic regions.

Community-Wide Active Case Finding for Tuberculosis: Time to Use the Evidence We Have

Tuberculosis, caused by the Mycobacterium tuberculosis (Mtb) bacteria, is one of the world's deadliest infectious diseases. Despite being the world's oldest pandemic, tuberculosis is very much a challenge of the modern era. In high-incidence settings, all people are at risk, irrespective of whether they have common vulnerabilities to the disease warranting the current WHO recommendations for community-wide tuberculosis active case finding in these settings. Despite good evidence of effectiveness in reducing tuberculosis transmission, uptake of this strategy has been lacking in the communities that would derive greatest benefit. We consider the various complexities in eliminating tuberculosis from the first principles of the disease, including diagnostic and other challenges that must be navigated under an elimination agenda. We make the case that community-wide tuberculosis active case finding is the best strategy currently available to drive elimination forward in high-incidence settings and that no time should be lost in its implementation. Recognizing that high-incidence communities vary in their epidemiology and spatiosocial characteristics, tuberculosis research and funding must now shift towards radically supporting local implementation and operational research in communities. This "preparing of the ground" for scaling up to community-wide intervention centers the local knowledge and local experience of community epidemiology to optimize implementation practices and accelerate reductions in community-level tuberculosis transmission.

Present outlooks on the prevalence of minimal and subclinical tuberculosis and current diagnostic tests: A systematic review and meta-analysis

BACKGROUND

Tuberculosis (TB) is a major global health issue, particularly in its minimal and subclinical forms, which often go undetected and contribute to transmission. Accurate prevalence assessment of these forms and the effectiveness of diagnostic tests are crucial for improving TB control, especially in high-risk populations such as those with HIV.

OBJECTIVES

This study aimed to determine the prevalence of minimal and subclinical TB and evaluate the positivity rates of current diagnostic tests.

METHODS

We conducted a meta-analysis of studies published from January 2000 to December 2022. Prevalence rates and diagnostic test results, including sputum culture, smear microscopy, TST/IGRA, and chest X-ray, were analyzed, with pooled prevalence calculated and comparisons made between geographic regions.

RESULTS

Minimal TB prevalence ranged from 0.9 % to 22.9 % in the general population, while subclinical TB prevalence was 0.05 % to 0.64 %, and 1.57 % to 14.63 % among individuals with HIV. The overall pooled prevalence of minimal TB was 7 % (95 % CI: 5-9 %), with higher rates in Asia (8 %, 95 % CI: 5-12 %) compared to Africa (6 %, 95 % CI: 4-8 %). Subclinical TB had a pooled prevalence of 0.2 % (95 % CI: 0.2-0.3 %) overall and 52 % (95 % CI: 46-58 %) among TB cases, with higher rates in Asia (60 %) compared to Africa (44 %). Diagnostic test positivity was 77 % (sputum culture), 15 % (smear microscopy), 64 % (TST/IGRA), and 53 % (chest X-ray).

CONCLUSIONS

This study reveals significant variability in the prevalence of minimal and subclinical TB. The findings highlight the need for improved diagnostic methods to reduce undetected cases, especially in high-risk populations.

Higher blood manganese level associated with increased risk of adult latent tuberculosis infection in the US population

Background

The associations between blood heavy metal levels and latent tuberculosis infection (LTBI) have not been fully elucidated. The aim of this study was to investigate the potential association between blood heavy metal levels and LTBI in adults using National Health and Nutrition Examination Survey data from 2011 to 2012.

Methods

We enrolled 1710 participants in this study, and compared the baseline characteristics of participants involved. Multivariate logistic regression analysis, restricted cubic splines (RCS) analysis, along with subgroup analysis and interaction tests were utilized to explore the association between blood manganese (Mn) level and LTBI risk.

Results

Participants with LTBI had higher blood Mn level compared to non-LTBI individuals (p < 0.05), while the levels of lead, cadmium, total mercury, selenium, copper, and zinc did not differ significantly between the two groups (p > 0.05). In the fully adjusted model, a slight increase in LTBI risk was observed with each 1-unit increase in blood Mn level (OR = 1.00, 95% CI: 1.00-1.01, p = 0.02). Participants in the highest quartile of blood Mn level had a threefold increase in LTBI risk compared to those in the lowest quartile (OR = 4.01, 95% CI: 1.22-11.33, p = 0.02). RCS analysis did not show a non-linear relationship between blood Mn level and LTBI (non-linear p-value = 0.0826). Subgroup analyses and interaction tests indicated that age, alcohol consumption, and income-to-poverty ratio significantly influenced LTBI risk (interaction p-values<0.05).

Conclusion

Individuals with LTBI had higher blood Mn level compared to non-LTBI individuals, and higher blood Mn level associated with increased LTBI risk.

Prevalence of subclinical pulmonary tuberculosis in adults in community settings: an individual participant data meta-analysis

BACKGROUND

Subclinical pulmonary tuberculosis, which presents without recognisable symptoms, is frequently detected in community screening. However, the disease category is poorly clinically defined. We explored the prevalence of subclinical pulmonary tuberculosis according to different case definitions.

METHODS

We did a one-stage individual participant data meta-analysis of nationally representative surveys that were conducted in countries with high incidence of tuberculosis between 2007 and 2020, that reported the prevalence of pulmonary tuberculosis based on chest x-ray and symptom screening in participants aged 15 years and older. Screening and diagnostic criteria were standardised across the surveys, and tuberculosis was defined by positive Mycobacterium tuberculosis sputum culture. We estimated proportions of subclinical tuberculosis for three case definitions: no persistent cough (ie, duration ≥2 weeks), no cough at all, and no symptoms (ie, absence of cough, fever, chest pain, night sweats, and weight loss), both unadjusted and adjusted for false-negative chest x-rays and uninterpretable culture results.

FINDINGS

We identified 34 surveys, of which 31 were eligible. Individual participant data were obtained and included for 12 surveys (620 682 participants) across eight countries in Africa and four in Asia. Data on 602 863 participants were analysed, of whom 1944 had tuberculosis. The unadjusted proportion of subclinical tuberculosis was 59·1% (n=1149/1944; 95% CI 55·8-62·3) for no persistent cough and 39·8% (773/1944; 36·6-43·0) for no cough of any duration. The adjusted proportions were 82·8% (95% CI 78·6-86·6) for no persistent cough and 62·5% (56·6-68·7) for no cough at all. In a subset of four surveys, the proportion of participants with tuberculosis but without any symptoms was 20·3% (n=111/547; 95% CI 15·5-25·1) before adjustment and 27·7% (95% CI 21·0-36·4) after adjustment. Tuberculosis without cough, irrespective of its duration, was more frequent among women (no persistent cough: adjusted odds ratio 0·79, 95% CI 0·63-0·97; no cough: adjusted odds ratio 0·76, 95% CI 0·62-0·93). Among participants with tuberculosis, 29·1% (95% CI 25·2-33·3) of those without persistent cough and 23·1% (18·8-27·4) of those without any cough had positive smear examinations.

INTERPRETATION

The majority of people in the community who have pulmonary tuberculosis do not report cough, a quarter report no tuberculosis-suggestive symptoms at all, and a quarter of those not reporting any cough have positive sputum smears, suggesting infectiousness. In high-incidence settings, subclinical tuberculosis could contribute considerably to the tuberculosis burden and to Mycobacterium tuberculosis transmission.

FUNDING

Mr Willem Bakhuys Roozeboom Foundation.

Chest Radiograph Screening for Detecting Subclinical Tuberculosis in Asymptomatic Household Contacts, Peru

The World Health Organization's end TB strategy promotes the use of symptom and chest radiograph screening for tuberculosis (TB) disease. However, asymptomatic early states of TB beyond latent TB infection and active disease can go unrecognized using current screening criteria. We conducted a longitudinal cohort study enrolling household contacts initially free of TB disease and followed them for the occurrence of incident TB over 1 year. Among 1,747 screened contacts, 27 (52%) of the 52 persons in whom TB subsequently developed during follow-up had a baseline abnormal radiograph. Of contacts without TB symptoms, persons with an abnormal radiograph were at higher risk for subsequent TB than persons with an unremarkable radiograph (adjusted hazard ratio 15.62 [95% CI 7.74-31.54]). In young adults, we found a strong linear relationship between radiograph severity and time to TB diagnosis. Our findings suggest chest radiograph screening can extend to detecting early TB states, thereby enabling timely intervention.

Classification of early tuberculosis states to guide research for improved care and prevention: an international Delphi consensus exercise

The current active-latent paradigm of tuberculosis largely neglects the documented spectrum of disease. Inconsistency with regard to definitions, terminology, and diagnostic criteria for different tuberculosis states has limited the progress in research and product development that are needed to achieve tuberculosis elimination. We aimed to develop a new framework of classification for tuberculosis that accommodates key disease states but is sufficiently simple to support pragmatic research and implementation. Through an international Delphi exercise that involved 71 participants representing a wide range of disciplines, sectors, income settings, and geographies, consensus was reached on a set of conceptual states, related terminology, and research gaps. The International Consensus for Early TB (ICE-TB) framework distinguishes disease from infection by the presence of macroscopic pathology and defines two subclinical and two clinical tuberculosis states on the basis of reported symptoms or signs of tuberculosis, further differentiated by likely infectiousness. The presence of viable Mycobacterium tuberculosis and an associated host response are prerequisites for all states of infection and disease. Our framework provides a clear direction for tuberculosis research, which will, in time, improve tuberculosis clinical care and elimination policies.

Determinants of tuberculosis disease development in children in central Ethiopia: A matched case-control study

BACKGROUND

The risk factors for tuberculosis (TB) disease development in children remained understudied, particularly in low-income countries like Ethiopia. The objective of this study was to identify determinants of TB disease development in general and in relation to BCG vaccination in children in central Ethiopia.

METHODS

We employed a 1:1 age-matched case-control design to compare the characteristics of children who developed TB (cases) with those who did not (controls). Data were collected in healthcare facilities in Addis Ababa city, Adama, and Bishoftu towns between September 25, 2021, and June 24, 2022. Two hundred and fifty-six cases were drawn at random from a list of childhood TB patients entered into SPSS software, and 256 controls were selected sequentially at triage from the same healthcare facilities where the cases were treated. A bivariate conditional logistic regression analysis was performed first to select candidate variables with p-values less than or equal to 0.20 for the multivariable model. Finally, variables with a p-value less than 0.05 for a matched adjusted odds ratio (mORadj) were reported as independent determinants of TB disease development.

RESULTS

The mean age of the cases was nine years, while that of the controls was 10 years. Males comprised 126 cases (49.2%) and 119 controls (46.5%), with the remainder being females. Ninety-nine (38.7%) of the cases were not BCG-vaccinated, compared to 58 (22.7%) of the controls. Household TB contact was experienced by 43 (16.8%) of the cases and 10 (3.9%) of the controls. Twenty-two (8.6%) of the cases and six (2.3%) of the controls were exposed to a cigarette smoker in their household. Twenty-two (8.6%) of the cases and three (1.2%) of the controls were positive for HIV. Children who were not vaccinated with BCG at birth or within two weeks of birth had more than twice the odds (mORadj = 2.11, 95% CI = 1.28-3.48) of developing TB compared to those who were. Children who ever lived with a TB-sick family member (mORadj = 4.28, 95% CI = 1.95-9.39), smoking family members (mORadj = 3.15, 95% CI = 1.07-9.27), and HIV-infected children (mORadj = 8.71, 95% CI = 1.96-38.66) also had higher odds of developing TB disease than their counterparts.

CONCLUSIONS

Being BCG-unvaccinated, having household TB contact, having a smoker in the household, and being HIV-infected were found to be independent determinants of TB disease development among children.

Subclinical tuberculosis: a meta-analysis of prevalence and scoping review of definitions, prevalence and clinical characteristics

BACKGROUND

This scoping review aimed to characterise definitions used to describe subclinical tuberculosis (TB), estimate the prevalence in different populations and describe the clinical characteristics and treatment outcomes in the scientific literature.

METHODS

A systematic literature search was conducted using PubMed. We included studies published in English between January 1990 and August 2022 that defined "subclinical" or "asymptomatic" pulmonary TB disease, regardless of age, HIV status and comorbidities. We estimated the weighted pooled proportions of subclinical TB using a random-effects model by World Health Organization reported TB incidence, populations and settings. We also pooled the proportion of subclinical TB according to definitions described in published prevalence surveys.

RESULTS

We identified 29 prevalence surveys and 71 other studies. Prevalence survey data (2002-2022) using "absence of cough of any duration" criteria reported higher subclinical TB prevalence than those using the stricter "completely asymptomatic" threshold. Prevalence estimates overlap in studies using other symptoms and cough duration. Subclinical TB in studies was commonly defined as asymptomatic TB disease. Higher prevalence was reported in high TB burden areas, community settings and immunocompetent populations. People with subclinical TB showed less extensive radiographic abnormalities, higher treatment success rates and lower mortality, although studies were few.

CONCLUSION

A substantial proportion of TB is subclinical. However, prevalence estimates were highly heterogeneous between settings. Most published studies incompletely characterised the phenotype of people with subclinical TB. Standardised definitions and diagnostic criteria are needed to characterise this phenotype. Further research is required to enhance case finding, screening, diagnostics and treatment options for subclinical TB.

Persistent Mycobacterium tuberculosis bioaerosol release in a tuberculosis-endemic setting

Pioneering studies linking symptomatic disease and cough-mediated release of Mycobacterium tuberculosis (Mtb) established the infectious origin of tuberculosis (TB), simultaneously informing the pervasive notion that pathology is a prerequisite for Mtb transmission. Our prior work has challenged this assumption: by sampling TB clinic attendees, we detected equivalent release of Mtb-containing bioaerosols by confirmed TB patients and individuals not receiving a TB diagnosis, and we demonstrated a time-dependent reduction in Mtb bioaerosol positivity during six-months' follow-up, irrespective of anti-TB chemotherapy. Now, by extending bioaerosol sampling to a randomly selected community cohort, we show that Mtb release is common in a TB-endemic setting: of 89 participants, 79.8% (71/89) produced Mtb bioaerosols independently of QuantiFERON-TB Gold status, a standard test for Mtb infection; moreover, during two-months' longitudinal sampling, only 2% (1/50) were serially Mtb bioaerosol negative. These results necessitate a reframing of the prevailing paradigm of Mtb transmission and infection, and may explain the current inability to elucidate Mtb transmission networks in TB-endemic regions.

Interferon-gamma release assay conversion after Mycobacterium tuberculosis exposure specifically associates with greater risk of progression to tuberculosis: A prospective cohort study in Leicester, UK

OBJECTIVES

We investigated whether quantifying the serial QuantiFERON-TB Gold (QFT) response improves tuberculosis (TB) risk stratification in pulmonary TB (PTB) contacts.

METHODS

A total of 297 untreated adult household PTB contacts, QFT tested at baseline and 3 months after index notification, were prospectively observed (median 1460 days). Normal variance of serial QFT responses was established in 46 extrapulmonary TB contacts. This informed categorisation of the response in QFT-positive PTB contacts as converters, persistently QFT-positive with significant increase (PPincrease), and without significant increase (PPno-increase).

RESULTS

In total, eight co-prevalent TB (disease ≤3 months after index notification) and 12 incident TB (>3 months after index notification) cases were diagnosed. Genetic linkage to the index strain was confirmed in all culture-positive progressors. The cumulative 2-year incident TB risk in QFT-positive contacts was 8.4% (95% confidence interval, 3.0-13.6%); stratifying by serial QFT response, significantly higher risk was observed in QFT converters (28%), compared with PPno-increase (4.8%) and PPincrease (3.7%). Converters were characterised by exposure to index cases with a shorter interval from symptom onset to diagnosis (median reduction 50.0 days, P = 0.013).

CONCLUSIONS

QFT conversion, rather than quantitative changes of a persistently positive serial QFT response, is associated with greater TB risk and exposure to rapidly progressive TB.

Reevaluating progression and pathways following Mycobacterium tuberculosis infection within the spectrum of tuberculosis

Traditional understanding of the risk of progression from Mycobacterium tuberculosis (Mtb) infection to tuberculosis (TB) overlooks diverse presentations across a spectrum of disease. We developed a deterministic model of Mtb infection and minimal (pathological damage but not infectious), subclinical (infectious but no reported symptoms), and clinical (infectious and symptomatic) TB, informed by a rigorous evaluation of data from a systematic review of TB natural history. Using a Bayesian approach, we calibrated the model to data from historical cohorts that followed tuberculin-negative individuals to tuberculin conversion and TB, as well as data from cohorts that followed progression and regression between disease states, disease state prevalence ratios, disease duration, and mortality. We estimated incidence, pathways, and 10-y outcomes following Mtb infection for a simulated cohort. Then, 92.0% (95% uncertainty interval, UI, 91.4 to 92.5) of individuals self-cleared within 10 y of infection, while 7.9% (95% UI 7.4 to 8.5) progressed to TB. Of those, 68.6% (95% UI 65.4 to 72.0) developed infectious disease, and 33.2% (95% UI 29.9 to 36.4) progressed to clinical disease. While 98% of progression to minimal disease occurred within 2 y of infection, only 71% and 44% of subclinical and clinical disease, respectively, occurred within this period. Multiple progression pathways from infection were necessary to calibrate the model and 49.5% (95% UI 45.6 to 53.7) of those who developed infectious disease undulated between disease states. We identified heterogeneous pathways across disease states after Mtb infection, highlighting the need for clearly defined disease thresholds to inform more effective prevention and treatment efforts to end TB.

Burden of Pulmonary Rifampicin-Resistant Tuberculosis in Kajiado, Kenya: An Observational Study

BACKGROUND

Rifampicin resistance (RR) is a major challenge in the clinical management of tuberculosis (TB), but data on its prevalence are still sparse in many countries. Our study aimed at estimating the prevalence of RR-TB in Kajiado County, Kenya. Secondary objectives were to estimate the incidence of pulmonary TB in adults and the rate of HIV-TB coinfection.

METHODS

We conducted an observational study in the context of the ATI-TB Project, carried out in Kajiado. The project was based on an active-case-finding campaign implemented with the aid of village chiefs, traditional healers and community health volunteers. Diagnosis relied on Xpert MTB/RIF, including a mobile machine that could be used to cover areas where testing would otherwise be difficult.

RESULTS

In sum, 3840 adults were screened for active TB during the campaign. RR cases among all TB diagnoses were 4.6%. The annual incidence of pulmonary TB among adults was 521 cases per 100,000 population. The rate of HIV coinfection was 22.2% among pulmonary TB diagnoses.

CONCLUSION

The prevalence of RR-TB was four times that what could be inferred from official notifications in Kajiado, and higher than overall prevalence in Kenya. In addition, our estimate of incidence of pulmonary TB in adults in Kajiado significantly differed from cases notified in the same area. In contrast, the rate of HIV coinfection was in line with national and regional data. TB diagnostic capability must be strengthened in Kajiado to improve patients' management and public health interventions.

The natural history of untreated pulmonary tuberculosis in adults: a systematic review and meta-analysis

Stages of tuberculosis disease can be delineated by radiology, microbiology, and symptoms, but transitions between these stages remain unclear. In a systematic review and meta-analysis of studies of individuals with untreated tuberculosis who underwent follow-up (34 cohorts from 24 studies, with a combined sample of 139 063), we aimed to quantify progression and regression across the tuberculosis disease spectrum by extracting summary estimates to align with disease transitions in a conceptual framework of the natural history of tuberculosis. Progression from microbiologically negative to positive disease (based on smear or culture tests) in participants with baseline radiographic evidence of tuberculosis occurred at an annualised rate of 10% (95% CI 6·2-13·3) in those with chest x-rays suggestive of active tuberculosis, and at a rate of 1% (0·3-1·8) in those with chest x-ray changes suggestive of inactive tuberculosis. Reversion from microbiologically positive to undetectable disease in prospective cohorts occurred at an annualised rate of 12% (6·8-18·0). A better understanding of the natural history of pulmonary tuberculosis, including the risk of progression in relation to radiological findings, could improve estimates of the global disease burden and inform the development of clinical guidelines and policies for treatment and prevention.