It Is Time to Focus on Asymptomatic Tuberculosis

Determining Thresholds for Computer-Aided Detection for Silicosis-An Analytic Approach

BACKGROUND

Computer-aided detection (CAD) is emerging as an adjunct to the use of the chest X-ray (CXR) in screening for pulmonary tuberculosis (TB). CAD for silicosis, a fibrotic lung disease due to silica dust and a strong risk factor for TB, is at an earlier stage of development and, unlike TB, depends on expert human reading for validation. For all CAD systems, an important step is the choice of threshold for classifying images as positive or negative for the disease in question. The objective of this article is to present an analytic approach to the choice of threshold in using CAD systems for silicosis.

METHODS

Drawing on receiver operating curve data from a published study on agreement between CAD and two expert readings of silicosis, two criteria for choosing the sensitivity/specificity combination were compared-the Youden Index and a minimum sensitivity of 90%. We explore the impact of criterion selection, silicosis definition, and reader on the choice and interpretation of threshold, as well as the influence of positive predictive value (PPV) derived from screen prevalence. We present a novel technique for using two CAD thresholds to distinguish images with a high likelihood of being of positive or negative from those characterized by uncertainty.

RESULTS

The sample was 501 CXR images from ex-gold miners. Derived thresholds varied across the two criteria, as well as across silicosis definition and expert reader. Varying the notional disease prevalence produced large differences in PPV and, therefore, proportions of false positives. The implications of these variations affecting threshold choice are described for three use cases-annual screening of active miners, outreach screening of former miners, and adjudication of claims for silicosis compensation.

CONCLUSION

In applying CAD to silicosis, users need to establish the use case, their preference for the sensitivity/specificity trade-off, and the silicosis definition, as well as considering the effect of disease prevalence. System developers need to take inter-reader variation in validation exercises into account and present this information transparently. A two-threshold model has potential utility in situations of high screening volume where there is a significant cost associated with referral for confirmation of diagnosis.

Unrecognized Tuberculosis: Risk Factors for Smear-Positive/Cavitary Asymptomatic Cases

Background

Screening patients with asymptomatic active tuberculosis (TB) is crucial as they can transmit the disease. Identifying the risk factors for transmission is essential for targeted screening. Understanding how the infectiousness of asymptomatic patients with TB affects disease outcomes is crucial for developing strategies to control TB spread.

Methods

We analyzed the national Korean TB cohort data to determine the factors associated with transmission risk and clinical outcomes in patients with asymptomatic pulmonary TB. The primary outcome was the factors associated with a risk factor for transmission, while the secondary outcome was mortality in asymptomatic patients with pulmonary TB stratified by transmission risk.

Results

Among 20 455 patients with pulmonary TB, 7434 (36.4%) were asymptomatic, while 1520 (25.5%) had potential transmission risks, indicated by a positive sputum acid-fast bacillus smear test or cavitation on chest radiographs. The factors associated with a higher transmission risk included male sex (odds ratio [OR], 1.385; 95% CI, 1.172-1.636; P < .001), low body mass index (BMI; OR, 1.687; 95% CI, 1.420-2.004; P < .001), current smoking (OR, 1.443; 95% CI, 1.213-1.716; P < .001), diabetes (OR, 1.399; 95% CI, 1.201-1.629; P < .001), and autoimmune disease (OR, 2.233; 95% CI, 1.295-3.850; P = .004). The mortality rate was higher in patients with a risk factor for transmission risk than in those without (9.3 vs 7.1%; P = .008).

Conclusions

Lean, smoking men with asymptomatic TB who have DM and/or autoimmune diseases have higher transmission and mortality risk. Asymptomatic populations with these risk factors warrant targeted screening.

The asymptomatic tuberculosis proportion among the elderly population: a systematic review and meta-analysis

BACKGROUND

The elderly population is a high-risk group for tuberculosis, and increasing evidence demonstrates a comparatively high proportion of asymptomatic tuberculosis in this group. This study aimed to determine the proportion of asymptomatic tuberculosis among patients with active tuberculosis through active case finding in the elderly population.

MATERIALS AND METHODS

We searched for relevant articles published from the establishment of each database to December 31, 2023 in Web of Science, PubMed, VIP database, Chinese National Knowledge Infrastructure, and Wanfang database. The studies' quality was assessed using the Agency for Healthcare Research and Quality's criteria. We used the I² statistic and Q test to evaluate heterogeneity across the included studies. We employed subgroup analysis, sensitivity analysis, and meta-regression to pinpoint sources of heterogeneity. Moreover, Begg's and Egger's tests were employed to detect any potential publication biases.

RESULTS

Nine studies involving 364,260 elderly individuals met the criteria for the analysis. In active case finding, the proportion of asymptomatic tuberculosis in the elderly population was 67.7% (95% CI: 54.7-79.5%, I2random effects model = 90.197, P < 0.001). The subgroup analysis revealed that the proportion of asymptomatic tuberculosis in high-burden countries was high, at 66.3% (95%CI: 52.5-78.9%, P < 0.001). Studies using multiple screening strategies including chest X-ray showed a higher percentage of asymptomatic patients, at 67.6% (95% CI: 51.1-82.1%, P < 0.001). However, in studies conducted after 2019 and studies with large sample sizes (≥ 15,000), the proportion of asymptomatic tuberculosis decreased (54.3%, 95%CI: 48.6-60.1%; and 62.3%, 95%CI: 45.9-77.4%, respectively).

CONCLUSIONS

The latest results revealed a significantly high percentage of elderly individuals with asymptomatic tuberculosis. This study highlighted the importance of mass screening to identify active tuberculosis cases in this specific group which could help health policymakers develop better strategies to reduce the burden of tuberculosis in the elderly population.

Clinical features of Tibetan adolescent tuberculosis at high altitudes: a retrospective study

BACKGROUND

Adolescent pulmonary tuberculosis (TB) is considered inadequately recognized and underreported at high altitudes. This study aimed to investigate the clinical features of adolescent pulmonary TB patients at high altitudes in China.

METHOD

A retrospective analysis was performed at Linzhi People's Hospital. Patients recruited were newly diagnosed with pulmonary TB. Detailed information, including demographics, medical history, presenting symptoms, laboratory results and pulmonary images, was collected. Sputum samples were collected to detect Mycobacterium tuberculosis via the GeneXpert MTB/RIF assay.

RESULT

A total of 63 adolescents and 192 adults were recruited. Compared with those in the adult group, typical TB-related manifestations were significantly less common in the adolescent group (all P < 0.05). The adolescent group had significantly more subclinical TB (23.8% vs. 8.3%, P = 0.001) and a higher previous tuberculosis exposure rate (38.8% vs. 8.3%, P < 0.001) than did the adult group. The erythrocyte sedimentation rate was significantly higher in the adolescent group than in the adult group (P = 0.026). Compared with adult patients, adolescent patients presented a lower rate of pleural thickening (P < 0.01). Compared with active adolescent patients, there were more female than male in the adolescent subclinical TB group (12/15 vs 27/48) and the positive rate of the sputum GeneXpert test was higher in subclinical TB group (6/15 vs 8/48).

CONCLUSION

Adolescent patients with pulmonary TB at high altitudes were prone to subclinical TB and have a higher previous TB exposure rate. Sputum GeneXpert test and ESR were important for the diagnosis of subclinical pulmonary TB.

Altered intestinal microbiota and fecal metabolites in patients with latent and active pulmonary tuberculosis

BACKGROUND

Pulmonary tuberculosis (PTB) is the main cause of infection-related mortality and the most common infectious disease that develops resistance to antibiotics. Gut microbiota and their associated metabolites are assumed to induce and influence the development of PTB. However, the alterations of gut microbiota and metabolites in TB patients is currently unclear.

METHODS

Fecal samples were collected from 13 PTB patients, 13 LTBI patients, and 13 healthy controls (HC). 16S rRNA sequencing and metabolomics were used to analyze the changes in the intestinal microbiota and the composition of fecal metabolites in groups.

RESULTS

Our findings indicated that the α-diversity of the gut microbiota in patients with PTB and LTBI decreases compared to HC, and at the phylum level, the relative abundance of Firmicutes decreases and the relative abundance of Bacteroides increases. And six genera were notably enriched in PTB patients and four in LTBI patients. Metabolomic analysis showed alterations in metabolite levels, such as short-chain fatty acids and amino acids.

CONCLUSIONS

we comprehensively explored the changes in the gut microbes and fecal metabolites in patients with PTB and LTBI from the perspective of the gut microbiota, which may provide potential diagnostic biomarkers and therapeutic targets for TB diagnosis and treatment.

Assessing the propensity of TB clinical isolates to form viable but non-replicating subpopulations

Current tuberculosis (TB) treatment is typically effective against drug-susceptible Mycobacterium tuberculosis, but can fail due to acquired drug resistance or phenotypic resistance. M. tuberculosis persisters, a subpopulation of viable but non-replicating (VBNR) antibiotic-tolerant bacteria, are thought to contribute to poor TB treatment outcomes. In this exploratory study, we investigated treatment-naïve drug-susceptible clinical isolates collected from people with TB, who subsequently had unsuccessful treatment outcomes. These were compared to isolates from cured individuals in terms of their ability to form VBNR subpopulations. Clinical isolates from individuals with unfavorable treatment outcomes form larger subpopulations of VBNR M. tuberculosis (2.67-13.71%) than clinical isolates from cured cases (0- 1.63%) following infection of THP-1 macrophages. All isolates were drug susceptible based on phenotypic and genotypic analysis. Whole genome sequencing identified 23 non-synonymous genomic variants shared by treatment failure clinical isolates, that were not present in isolates from cured cases. This exploratory study highlights the ability of treatment-naïve clinical isolates to form heterogeneous populations containing VBNR M. tuberculosis. We also demonstrate that clinical isolates from individuals with unsuccessful treatment outcomes form higher percentages of VBNR M. tuberculosis. The findings of this exploratory study suggest that an increased propensity to form VBNR subpopulations may impact TB treatment outcome.

Current approaches for diagnosis of subclinical pulmonary tuberculosis, clinical implications and future perspectives: a scoping review

INTRODUCTION

Subclinical tuberculosis (TB) is the presence of TB disease among people who are either asymptomatic or have minimal symptoms.

AREAS COVERED

Currently, there are no accurate diagnostic tools and clear treatment approaches for subclinical TB. In this study, a comprehensive literature search was conducted across major databases. This review aimed to uncover the latest advancements in diagnostic approaches, explore their clinical implications, and outline potential future perspectives. While innovative technologies are in development to enable sputum-free TB tests, there remains a critical need for precise diagnostic tools tailored to the unique characteristics of subclinical TB. Given the complexity of subclinical TB, a multidisciplinary approach involving clinicians, microbiologists, epidemiologists, and public health experts is essential. Further research is needed to establish standardized diagnostic criteria and treatment guidelines specifically tailored for subclinical TB, acknowledging the unique challenges posed by this elusive stage of the disease.

EXPERT OPINION

Efforts are needed for the detection, diagnosis, and treatment of subclinical TB. In this review, we describe the importance of subclinical TB, both from a clinical and public health perspective and highlight the diagnostic and treatment gaps of this stage.

Diagnostic accuracy of a sequence-specific Mtb-DNA hybridization assay in urine: a case-control study including subclinical TB cases

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) remains one of the deadliest infectious diseases globally. Timely diagnosis is a key step in the management of TB patients and in the prevention of further transmission events. Current diagnostic tools are limited in these regards. There is an urgent need for new accurate non-sputum-based diagnostic tools for the detection of symptomatic as well as subclinical TB. In this study, we recruited 52 symptomatic TB patients (sputum Xpert MTB/RIF positive) and 58 household contacts to assess the accuracy of a sequence-specific hybridization assay that detects the presence of Mtb cell-free DNA in urine. Using sputum Xpert MTB/RIF as a reference test, the magnetic bead-capture assay could discriminate active TB from healthy household contacts with an overall sensitivity of 72.1% [confidence interval (CI) 0.59-0.86] and specificity of 95.5% (CI 0.90-1.02) with a positive predictive value of 93.9% and negative predictive value of 78.2%. The detection of Mtb-specific DNA in urine suggested four asymptomatic TB infection cases that were confirmed in all instances either by concomitant Xpert MTB/RIF sputum testing or by follow-up investigation raising the specificity of the index test to 100%. We conclude that sequence-specific hybridization assays on urine specimens hold promise as non-invasive tests for the detection of subclinical TB.

IMPORTANCE

There is an urgent need for a non-sputum-based diagnostic tool allowing sensitive and specific detection of all forms of tuberculosis (TB) infections. In that context, we performed a case-control study to assess the accuracy of a molecular detection method enabling the identification of cell-free DNA from Mycobacterium tuberculosis that is shed in the urine of tuberculosis patients. We present accuracy data that would fulfill the target product profile for a non-sputum test. In addition, recent epidemiological data suggested that up to 50% of individuals secreting live bacilli do not present with symptoms at the time of screening. We report, here, that the investigated index test could also detect instances of asymptomatic TB infections among household contacts.

Subclinical tuberculosis linkage to care and completion of treatment following community-based screening in rural South Africa

Background

Tuberculosis (TB), a leading cause of infectious death, is curable when patients complete a course of multi-drug treatment. Because entry into the TB treatment cascade usually relies on symptomatic individuals seeking care, little is known about linkage to care and completion of treatment in people with subclinical TB identified through community-based screening.

Methods

Participants of the Vukuzazi study, a community-based survey that provided TB screening in the rural uMkhanyakude district of KwaZulu-Natal from May 2018 - March 2020, who had a positive sputum (GeneXpert or Mtb culture, microbiologically-confirmed TB) or a chest x-ray consistent with active TB (radiologically-suggested TB) were referred to the public health system. Telephonic follow-up surveys were conducted from May 2021 - January 2023 to assess linkage to care and treatment status. Linked electronic TB register data was accessed. We analyzed the effect of baseline HIV and symptom status (by WHO 4-symptom screen) on the TB treatment cascade.

Results

Seventy percent (122/174) of people with microbiologically-confirmed TB completed the telephonic survey. In this group, 84% (103/122) were asymptomatic and 46% (56/122) were people living with HIV (PLWH). By self-report, 98% (119/122) attended a healthcare facility after screening, 94% (115/122) started TB treatment and 93% (113/122) completed treatment. Analysis of electronic TB register data confirmed that 67% (116/174) of eligible individuals started TB treatment. Neither symptom status nor HIV status affected linkage to care. Among people with radiologically-suggested TB, 48% (153/318) completed the telephonic survey, of which 80% (122/153) were asymptomatic and 52% (79/153) were PLWH. By self-report, 75% (114/153) attended a healthcare facility after screening, 16% (24/153) started TB treatment and 14% (22/153) completed treatment. Nine percent (28/318) of eligible individuals had TB register data confirming that they started treatment.

Conclusions

Despite high rates of subclinical TB, most people diagnosed with microbiologically-confirmed TB after community-based screening were willing to link to care and complete TB treatment. Lower rates of linkage to care in people with radiologically-suggested TB highlight the importance of streamlined care pathways for this group. Clearer guidelines for the management of people who screen positive during community-based TB screening are needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s44263-024-00059-0.

Mirage de tuberculose in the 21st century

The occurrence of transient culture positivity for Mycobacterium tuberculosis (MTB), known as mirage de tuberculose, poses significant challenges in understanding its spectrum and implications. Here, we report a case of transient culture positivity, oscillating between detectable and non-detectable MTB cultures with minimal radiological features and review the literature on this phenomenon. The scarcity of scientific literature on this subject stems from the inherent impossibility of systematically studying mirage de tuberculose. Ethical and public health concerns prevent withholding treatment to monitor spontaneous reversion to negative cultures. Based on the literature, we estimate that mirage de tuberculose occurs in approximately one-third of individuals infected with MTB who exhibit no symptoms. Despite the inherently limited nature of these findings, they suggest that the significance of mirage de tuberculose may be greater than currently perceived. Managing cases of mirage de tuberculose presents formidable challenges from a public health perspective. Striking a balance between prompt treatment initiation to prevent transmission and the risk of unnecessary treatment requires careful consideration. In conclusion, mirage de tuberculose remains a poorly understood clinical entity with very limited literature available. Advancing research and interdisciplinary collaborations are essential to unravel the intricacies of this phenomenon and develop effective strategies to address its public health challenges.

Point-of-care C-reactive protein and Xpert MTB/RIF Ultra for tuberculosis screening and diagnosis in unselected antiretroviral therapy initiators: a prospective, cross-sectional, diagnostic accuracy study

BACKGROUND

Tuberculosis, a major cause of death in people living with HIV, remains challenging to diagnose. Diagnostic accuracy data are scarce for promising triage and confirmatory tests such as C-reactive protein (CRP), sputum and urine Xpert MTB/RIF Ultra (Xpert Ultra), and urine Determine TB LAM Ag (a lateral flow lipoarabinomannan [LF-LAM] test), without symptom selection. We evaluated novel triage and confirmatory tests in ambulatory people with HIV initiating antiretroviral therapy (ART).

METHODS

897 ART-initiators were recruited irrespective of symptoms and sputum induction offered. For triage (n=800), we evaluated point-of-care blood-based CRP testing, compared with the WHO-recommended four-symptom screen (W4SS). For sputum-based confirmatory testing (n=787), we evaluated Xpert Ultra versus Xpert MTB/RIF (Xpert). For urine-based confirmatory testing (n=732), we evaluated Xpert Ultra and LF-LAM. We used a sputum culture reference standard.

FINDINGS

463 (52%) of 897 participants were female. The areas under the receiver operator characteristic curves for CRP was 0·78 (95% CI 0·73-0·83) and for number of W4SS symptoms was 0·70 (0·64-0·75). CRP (≥10 mg/L) had similar sensitivity to W4SS (77% [95% CI 68-85; 80/104] vs 77% [68-85; 80/104]; p>0·99] but higher specificity (64% [61-68; 445/696] vs 48% [45-52; 334/696]; p<0·0001]; reducing unnecessary confirmatory testing by 138 (95% CI 117-160) per 1000 people and number-needed-to-test from 6·91 (95% CI 6·25-7·81) to 4·87 (4·41-5·51). Sputum samples with Xpert Ultra, which required induction in 49 (31%) of 158 of people (95% CI 24-39), had higher sensitivity than Xpert (71% [95% CI 61-80; 74/104] vs 56% [46-66; 58/104]; p<0·0001). Of the people with one or more confirmatory sputum or urine test results that were positive, the proportion detected by Xpert Ultra increased from 45% (26-64) to 66% (46-82) with induction. Programmatically done haemoglobin, triage test combinations, and urine tests showed comparatively worse results.

INTERPRETATION

CRP is a more specific triage test than W4SS in those initiating ART. Sputum induction improves diagnostic yield. Sputum samples with Xpert Ultra is a more accurate confirmatory test than with Xpert.

FUNDING

South African Medical Research Council, EDCTP2, US National Institutes of Health-National Institute of Allergy and Infectious Diseases.

Tuberculosis and COVID-19 in the elderly: factors driving a higher burden of disease

Mycobacterium tuberculosis (M.tb) and SARS-CoV-2 are both infections that can lead to severe disease in the lower lung. However, these two infections are caused by very different pathogens (Mycobacterium vs. virus), they have different mechanisms of pathogenesis and immune response, and differ in how long the infection lasts. Despite the differences, SARS-CoV-2 and M.tb share a common feature, which is also frequently observed in other respiratory infections: the burden of disease in the elderly is greater. Here, we discuss possible reasons for the higher burden in older adults, including the effect of co-morbidities, deterioration of the lung environment, auto-immunity, and a reduced antibody response. While the answer is likely to be multifactorial, understanding the main drivers across different infections may allow us to design broader interventions that increase the health-span of older people.

Spectrum of TB Disease and Treatment Outcomes in a Mobile Community Based Active Case Finding Program in Yogyakarta Province, Indonesia

The World Health Organization recommends using chest X-ray (CXR) in active case finding (ACF) to improve case detection. This study aimed to describe the spectrum and outcomes of TB disease diagnosed through a mobile community based ACF program in Yogyakarta. This prospective cohort study included people attending a TB ACF program in Yogyakarta between 1 January 2021 to 30 June 2022. Participants ≥10 years old underwent CXR, symptom screening, and Xpert MTB/RIF testing of sputum. Subclinical TB was defined as asymptomatic active TB, whether bacteriologically confirmed or not. Treatment outcome data were obtained from the national program TB database. 47,735 people attended the ACF program; the yield of TB disease was 0.86% (393/45,938). There were 217 symptomatic cases, of whom 72 (33.2%) were bacteriologically confirmed, and 176 asymptomatic cases, with 52 (29.5%) bacteriologically confirmed. Treatment success was 70.7% with high loss to follow up (9%) and not evaluated (17.1%). Multivariate analysis demonstrated weak evidence for lower unsuccessful outcomes in symptomatic versus subclinical TB (aOR 0.6, 95% CI 0.36-0.998). TB ACF programs utilizing CXR may diagnose a high proportion of subclinical TB. Linkage to care in ACF program is important to increase successful treatment outcomes.

A Machine Learning-Based Analytic Pipeline Applied to Clinical and Serum IgG Immunoproteome Data To Predict Chlamydia trachomatis Genital Tract Ascension and Incident Infection in Women

We developed a reusable and open-source machine learning (ML) pipeline that can provide an analytical framework for rigorous biomarker discovery. We implemented the ML pipeline to determine the predictive potential of clinical and immunoproteome antibody data for outcomes associated with Chlamydia trachomatis (Ct) infection collected from 222 cis-gender females with high Ct exposure. We compared the predictive performance of 4 ML algorithms (naive Bayes, random forest, extreme gradient boosting with linear booster [xgbLinear], and k-nearest neighbors [KNN]), screened from 215 ML methods, in combination with two different feature selection strategies, Boruta and recursive feature elimination. Recursive feature elimination performed better than Boruta in this study. In prediction of Ct ascending infection, naive Bayes yielded a slightly higher median value of are under the receiver operating characteristic curve (AUROC) 0.57 (95% confidence interval [CI], 0.54 to 0.59) than other methods and provided biological interpretability. For prediction of incident infection among women uninfected at enrollment, KNN performed slightly better than other algorithms, with a median AUROC of 0.61 (95% CI, 0.49 to 0.70). In contrast, xgbLinear and random forest had higher predictive performances, with median AUROC of 0.63 (95% CI, 0.58 to 0.67) and 0.62 (95% CI, 0.58 to 0.64), respectively, for women infected at enrollment. Our findings suggest that clinical factors and serum anti-Ct protein IgGs are inadequate biomarkers for ascension or incident Ct infection. Nevertheless, our analysis highlights the utility of a pipeline that searches for biomarkers and evaluates prediction performance and interpretability. IMPORTANCE Biomarker discovery to aid early diagnosis and treatment using machine learning (ML) approaches is a rapidly developing area in host-microbe studies. However, lack of reproducibility and interpretability of ML-driven biomarker analysis hinders selection of robust biomarkers that can be applied in clinical practice. We thus developed a rigorous ML analytical framework and provide recommendations for enhancing reproducibility of biomarkers. We emphasize the importance of robustness in selection of ML methods, evaluation of performance, and interpretability of biomarkers. Our ML pipeline is reusable and open-source and can be used not only to identify host-pathogen interaction biomarkers but also in microbiome studies and ecological and environmental microbiology research.

Point-of-care C-reactive protein and Xpert MTB/RIF Ultra for tuberculosis screening and diagnosis in unselected antiretroviral therapy initiators: a prospective diagnostic accuracy study

Background

Tuberculosis (TB), a major cause of death in people living with HIV (PLHIV), remains challenging to diagnose. Diagnostic accuracy data are lacking for promising triage tests, such as C-reactive protein (CRP), and confirmatory tests, such as sputum and urine Xpert MTB/RIF Ultra (Ultra), and urine LAM, without prior symptom selection.

Methods

897 PLHIV initiating antiretroviral therapy were consecutively recruited in settings with high TB incidence, irrespective of symptoms. Participants were offered sputum induction, with a liquid culture reference standard. First, we evaluated point-of-care CRP testing on blood, compared to the World Health Organization (WHO)-recommended four-symptom screen (W4SS) for triage (n=800). Second, we evaluated Xpert MTB/RIF Ultra (Ultra) versus Xpert MTB/RIF (Xpert) for sputum-based confirmatory testing (n=787), with or without sputum induction. Third, we evaluated Ultra and Determine LF-LAM for urine-based confirmatory testing (n=732).

Findings

CRP and number of W4SS symptoms had areas under the receiver operator characteristic curve of 0.78 (95% confidence interval 0.73, 0.83) and 0.70 (0.64, 0.75), respectively. For triage, CRP (≥10 mg/l) has similar sensitivity to W4SS [77% (68, 85) vs. 77% (68, 85); p>0.999] but higher specificity [64% (61, 68) vs. 48% (45, 52); p<0.001]; reducing unnecessary confirmatory testing by 138 per 1000 people and the number-needed-to-test from 6.91 (6.25, 7.81) to 4.87 (4.41, 5.51). Using sputum, which required induction in 31% (24, 39) of people, Ultra had higher sensitivity than Xpert [71% (61, 80) vs. 56% (46, 66); p<0.001] but lower specificity [98% (96, 100) vs. 99% (98, 100); p<0.001]. The proportion of people with ≥1 positive confirmatory result detected by Ultra increased from 45% (26, 64) to 66% (46, 82) when induction was done. Programmatically-done haemoglobin, triage test combinations, and urine tests showed comparatively worse performance.

Interpretation

Among ART-initiators in a high burden setting, CRP is a more specific triage test than W4SS. Sputum induction improves yield. Sputum Ultra is a more accurate confirmatory test than Xpert.

Funding

SAMRC (MRC-RFA-IFSP-01-2013), EDCTP2 (SF1401, OPTIMAL DIAGNOSIS), NIH/NIAD (U01AI152087).

Research in context

Evidence before this study: Novel triage and confirmatory tests are urgently needed for TB, especially in key risk groups like PLHIV. Many TB cases do not meet World Health Organization (WHO)-recommended four-symptom screen (W4SS) criteria despite accounting for significant transmission and morbidity. W4SS also lacks specificity, which makes onward referral of triage-positive people for expensive confirmatory testing inefficient and hampers diagnostic scale-up. Alternative triage approaches like CRP have promise, but have comparatively little data in ART-initiators, especially when done without syndromic preselection and using point-of-care (POC) tools. After triage, confirmatory testing can be challenging due to sputum scarcity and paucibacillary early-stage disease. Next generation WHO-endorsed rapid molecular tests (including Xpert MTB/RIF Ultra; Ultra) are a standard-of-care for confirmatory testing. However, there are no supporting data in ART-initiators, among whom Ultra may offer large sensitivity gains over predecessors like Xpert MTB/RIF (Xpert). The added value of sputum induction to augment diagnostic sampling for confirmatory testing is also unclear. Lastly, the performance of urine tests (Ultra, Determine LF-LAM) in this population requires more data.Added value of this study: We evaluated repurposed and new tests for triage and confirmatory testing using a rigorous microbiological reference standard in a highly vulnerable high-priority patient population (ART-initiators) regardless of symptoms and ability to naturally expectorate sputum. We showed POC CRP triage is feasible, performs better than W4SS, and that combinations of different triage approaches offer no advantages over CRP alone. Sputum Ultra has superior sensitivity to Xpert; often detecting W4SS-negative TB. Furthermore, without induction, confirmatory sputum-based testing would not be possible in a third of people. Urine tests had poor performance. This study contributed unpublished data to systematic reviews and meta-analyses used by the WHO to inform global policy supporting use of CRP triage and Ultra in PLHIV.Implication of all the available evidence: POC CRP triage testing is feasible and superior to W4SS and, together with sputum induction in people who triage CRP-positive should, after appropriate cost and implementation research, be considered for roll-out in ART-initiators in high burden settings. Such people should be offered Ultra, which outperforms Xpert.

Subclinical ankle joint tuberculous arthritis - The role of scintigraphy: A case series

BACKGROUND

Tuberculosis remains a complicated problem. A lack of awareness accompanied by difficulty in diagnosis hinders the management of tuberculosis. Delayed management, particularly in osteoarticular regions, results in unnecessary procedures, including joint-sacrificing surgery.

CASE SUMMARY

Three cases of subclinical ankle joint tuberculosis without clear signs of tuberculosis were presented. The efficacy of technetium-99m-ethambutol scintigraphy in diagnosing early-stage tuberculous arthritis is reported.

CONCLUSION

The reports suggested that scintigraphy is recommended to diagnose subclinical tuberculous arthritis, especially in tuberculosis endemic regions.

Difficulties in distinguishing silicosis and pulmonary tuberculosis in silica-exposed gold miners: A report of four cases

Silicosis and tuberculosis (TB) are both global health concerns, with high prevalence among miners from the South African gold mines. Although knowledge has accumulated about these two conditions as distinct diseases since the early 20th century, and despite progress in technology with multiple diagnostic tools and treatment options available for TB, the challenge of distinguishing and therefore efficiently managing these two conditions in this population remains as current as it was 100 years ago. To illustrate the diagnostic and health service problems of distinguishing TB and silicosis clinically and radiologically in former gold miners from the South African mines living in resource-poor areas, we discuss four cases reviewed for this report by a panel of experts. For each case, occupational history, past and current medical history, physical examination, radiological and laboratory findings are described. Common themes are: (1) poor agreement between radiological and clinical presentation; (2) poor agreement between radiology findings and detection of active TB on sputum Xpert MTB/RIF testing; and (3) difficulty in distinguishing the clinical and radiological presentations of silicosis and tuberculosis. Possible consequences at the population level are undertreatment or overtreatment of TB, and underdiagnosis or overdiagnosis of silicosis. There is a need for training of practitioners who are screening or attending to former gold miners in the clinical and radiological features of combined disease, using a curated database of miners' chest X-ray images. Investment in protocols for management of both acute and chronic silicotuberculosis in ex-miners is needed, as is clinical, epidemiologic, and operations research.

Characterizing the Spectrum of Latent Mycobacterium tuberculosis in the Cynomolgus Macaque Model: Clinical, Immunologic, and Imaging Features of Evolution

Mycobacterium tuberculosis infection outcomes have been described as active tuberculosis or latent infection but a spectrum of outcomes is now recognized. We used a nonhuman primate model, which recapitulates human infection, to characterize the clinical, microbiologic, and radiographic patterns associated with developing latent M. tuberculosis infection. Four patterns were identified. "Controllers" had normal erythrocyte sedimentation rate (ESR) without M. tuberculosis growth in bronchoalveolar lavage or gastric aspirate (BAL/GA). "Early subclinicals" showed transient ESR elevation and/or M. tuberculosis growth on BAL/GA for 60 days postinfection, "mid subclinicals" were positive for 90 days, and "late subclinicals" were positive intermittently, despite the absence of clinical disease. Variability was noted regarding granuloma formation, lung/lymph node metabolic activity, lung/lymph node bacterial burden, gross pathology, and extrapulmonary disease. Like human M. tuberculosis infection, this highlights the heterogeneity associated with the establishment of latent infection, underscoring the need to understand the clinical spectrum and risk factors associated with severe disease.

Clinically encountered growth phenotypes of tuberculosis-causing bacilli and their in vitro study: A review

The clinical manifestations of tuberculosis (TB) vary widely in severity, site of infection, and outcomes of treatment-leading to simultaneous efforts to individualize therapy safely and to search for shorter regimens that can be successfully used across the clinical spectrum. In these endeavors, clinicians and researchers alike employ mycobacterial culture in rich media. However, even within the same patient, individual bacilli among the population can exhibit substantial variability in their culturability. Bacilli in vitro also demonstrate substantial heterogeneity in replication rate and cultivation requirements, as well as susceptibility to killing by antimicrobials. Understanding parallels in clinical, ex vivo and in vitro growth phenotype diversity may be key to identifying those phenotypes responsible for treatment failure, relapse, and the reactivation of bacilli that progresses TB infection to disease. This review briefly summarizes the current role of mycobacterial culture in the care of patients with TB and the ex vivo evidence of variability in TB culturability. We then discuss current advances in in vitro models that study heterogenous subpopulations within a genetically identical bulk culture, with an emphasis on the effect of oxidative stress on bacillary cultivation requirements. The review highlights the complexity that heterogeneity in mycobacterial growth brings to the interpretation of culture in clinical settings and research. It also underscores the intricacies present in the interplay between growth phenotypes and antimicrobial susceptibility. Better understanding of population dynamics and growth requirements over time and space promises to aid both the attempts to individualize TB treatment and to find uniformly effective therapies.

Testing and Treating Mycobacterium tuberculosis Infection

After infection with Mycobacterium tuberculosis, a minority of individuals will progress to tuberculosis disease (TB). The risk is higher among persons with well-established risk factors and within the first year after infection. Testing and treating individuals at high risk of progression maximizes the benefits of TB preventive therapy; avoiding testing of low-risk persons will limit potential harms. Several treatment options are available; rifamycin-based regimens offer the best efficacy-safety balance. In this review, we present an overview of the diagnosis and treatment of TB infection, and summarize common clinical scenarios.

Contributory Factors to Successful Tuberculosis Treatment in Southwest Nigeria: A Cross-Sectional Study

Tuberculosis (TB) is one of the oldest human diseases, and preventing treatment failure is critical. This is because TB cases pose a risk to the immediate and remote communities due to the potential for spread, particularly for multidrug-resistant (MDR) strains that have been associated with higher morbidity and mortality rates. Hence, this study looked at the factors that influence TB treatment outcomes in Southwest Nigeria. We conducted a cross-sectional study with 712 TB patients from 25 directly observed treatment short course (DOTS) centers, out of which 566 (79.49%) were new treatment cases, and 102 (14.33%) were retreatment cases. The outcome variable was computed into successful treatment where ‘Yes’ was assigned to TB treatment completed and cured, and ‘No’ was assigned to all the remaining outcomes following the standard TB definition. Independent variables included in the analysis were the patient’s socio-demographic characteristics (such as age, sex, distance from the facility, marital status, family type, education, and computed socioeconomic status from modified DHS household assets), clinical and facility parameters (such as the HIV status, facility of access to healthcare, healthcare workers attitudes, services offered at the facility, appearance of the facility, number of people seeking care and waiting time at the facility). Bivariate analysis showed that HIV status (OR: 3.53, 95% CI: 1.83–6.82; p = 0.001), healthcare worker attitude (OR: 2.13, 95% CI: 1.21–3.74; p = 0.01), services offered at the facility (OR: 0.67, 95% CI: 0.49–0.92; p = 0.01), appearance of facility (OR: 0.67, 95% CI: 0.46–0.98; p = 0.04), and number of people seeking care (OR: 2.47, 95% CI: 1.72–3.55; p = 0.001) were associated with higher odds of successful treatment outcome with statistical significance. After multivariate analysis, reactive HIV status (aOR: 3.37, 95% CI: 1.67–6.80; p = 0.001), positive attitude of healthcare workers (aOR: 2.58, 95% CI: 1.36–4.89; p = 0.04), excellent services offered at the healthcare facility (aOR: 0.53, 95% CI: 0.36–0.78; p = 0.001) and few people seeking care (aOR: 2.10, 95% CI: 1.21–3.84; p = 0.001) became independent significant determinants of successful treatment outcome. The study concluded that reactive HIV status, positive attitude of healthcare workers, few people seeking healthcare, and excellent service provided were all factors that contributed to successful treatment outcomes.

Additional Usefulness of Bronchoscopy in Patients with Initial Microbiologically Negative Pulmonary Tuberculosis: A Retrospective Analysis of a Korean Nationwide Prospective Cohort Study

Purpose

Bronchoscopy is widely used for microbiological diagnosis of patients with minimal sputum production. However, the usefulness of bronchoscopy in patient groups who benefit from subsequent microbiological confirmation has not been established.

Patients and Methods

We retrospectively analyzed Korean tuberculosis (TB) cohort data from September 2018 to October 2019 to evaluate the usefulness of bronchoscopy in patients with microbiologically negative pulmonary TB (based on initial sputum polymerase chain reaction and culture results). The primary outcome was the proportion of microbiological diagnoses made after bronchoscopy. Secondary outcomes were the predictors of microbiological confirmation and the percentage of additional resistance detection after bronchoscopy.

Results

A total of 5194 patients were diagnosed with pulmonary TB, 937 of whom were microbiologically negative for pulmonary TB based on the initial sputum findings. Of these, 319 patients underwent bronchoscopy, and further microbiological confirmation was achieved in 157 (49.1%) patients. The predictors of microbiological confirmation after bronchoscopy were age >65 years, female sex, and low body mass index (BMI). The rate of additional resistance detection was 10.5% (multidrug resistant/rifampin-resistant 3.8%; isoniazid-resistant 5.7%).

Conclusion

Bronchoscopy can be used for the detection of resistant pathogens. Bronchoscopy should be considered for microbiologically negative pulmonary TB in women aged >65 years and with low BMI for subsequent microbiological confirmation.

Recurrent subclinical tuberculosis among ART accessing participants: Incidence, clinical course, and outcomes

BACKGROUND

Undiagnosed asymptomatic subclinical tuberculosis (TB) remains a significant threat to global TB control and accounts for a substantial proportion of cases among people living with HIV/AIDS (PLWHA). We determined the incidence, progression, and outcomes of subclinical TB in anti-retroviral therapy (ART) accessing PLWHA with known previous TB in South Africa.

METHODS

A total of 402 adult PLWHA previously treated for TB were enrolled in the prospective CAPRISA TRuTH (TB Recurrence Upon TB and HIV treatment) study. Participants were screened for TB with quarterly clinical and bacteriologic evaluation and bi-annual chest radiographs over 36 months. Those with suspected or confirmed TB were referred to the National TB Programme. Participants received HIV services, including ART. Incidence rate of TB was estimated by Poisson regression, and descriptive statistical analyses summarised data.

RESULTS

A total of 48/402 (11.9%) bacteriologically confirmed incident recurrent TB cases was identified, comprising 17/48 (35.4%) subclinical TB cases and 31/48 (64.5%) clinical TB cases. Age, sex, and body mass index (BMI) were similar among subclinical , clinical , and no TB groups. Incidence rates of recurrent TB overall; in clinical TB; and subclinical TB groups was 2.3 [95% CI: 1.7-3.0]; 1.5 [95% CI: 1.1-2.2]; and 0.9 [95% CI: 0.5-1.4] per 100 person-years, respectively. In the subclinical TB group, 14/17 (82.4%) was diagnosed by TB culture only, 11/17 (64.7%) received TB treatment, and 6/17 (35.3%) resolved TB spontaneously.

CONCLUSION

The high incidence rates of recurrent subclinical TB in PLWHA highlight inadequacies of symptom-based TB screening in high TB-HIV burden settings.

Prevalence of Mycobacterium tuberculosis in sputum and reported symptoms among clinic attendees compared to a community survey in rural South Africa

BACKGROUND

Tuberculosis (TB) case finding efforts typically target symptomatic people attending health facilities. We compared the prevalence of Mycobacterium tuberculosis (Mtb) sputum culture-positivity among adult clinic attendees in rural South Africa with a concurrent, community-based estimate from the surrounding demographic surveillance area (DSA).

METHODS

Clinic: Randomly-selected adults (≥18 years) attending two primary healthcare clinics were interviewed and requested to give sputum for mycobacterial culture. HIV and antiretroviral therapy (ART) status were based on self-report and record review. Community: All adult (≥15 years) DSA residents were invited to a mobile clinic for health screening, including serological HIV testing; those with ≥1 TB symptom (cough, weight loss, night sweats, fever) or abnormal chest radiograph were asked for sputum.

RESULTS

Clinic: 2,055 patients were enrolled (76.9% female, median age 36 years); 1,479 (72.0%) were classified HIV-positive (98.9% on ART) and 131 (6.4%) reported ≥1 TB symptom. Of 20/2,055 (1.0% [95% CI 0.6-1.5]) with Mtb culture-positive sputum, 14 (70%) reported no symptoms. Community: 10,320 residents were enrolled (68.3% female, median age 38 years); 3,105 (30.3%) tested HIV-positive (87.4% on ART) and 1,091 (10.6%) reported ≥1 TB symptom. Of 58/10,320 (0.6% [95% CI 0.4-0.7]) with Mtb culture-positive sputum, 45 (77.6%) reported no symptoms.In both surveys, sputum culture positivity was associated with male sex and reporting >1 TB symptom.

CONCLUSIONS

In both clinic and community settings, most participants with Mtb culture-positive sputum were asymptomatic. TB screening based only on symptoms will miss many people with active disease in both settings.

Subclinical tuberculosis in children: diagnostic strategies for identification reported in a 6-year national prospective surveillance study

BACKGROUND

Subclinical tuberculosis (TB) is well recognized and defined as a disease state with absent or non-recognized symptoms. The study identifies factors associated with subclinical TB and diagnostic strategies in a low-burden, high-resource country.

METHODS

Data was collected between December 2013 to November 2019 through the Swiss Pediatric Surveillance Unit (SPSU). Children with culture/molecular confirmed TB, or who were treated with ≥3 anti-mycobacterial drugs, were included.

RESULTS

A total of 138 (80%) children with TB disease were included in the final analysis, of which 43 (31%) were subclinical. The median age of children with subclinical compared to symptomatic TB was 3.7(IQR 2.2 to 7) and 9.7(IQR 2.7 to 14.3) years, respectively (p=0.003). The cause of investigation for TB was recorded in 31/43 (72.1%) of children with subclinical TB, and included contact exposure in 25 (80.6%). In children with subclinical TB, diagnosis was made by a combination of the following abnormal/confirming results: culture/molecular + immunodiagnostic + chest radiography in 12 (27.9%), immunodiagnostic + chest radiography in 19 (44.2%), culture/molecular + chest radiography in 2 (4.7%), culture + immunodiagnostic in 1 (2.3%), chest radiography only in 8 (18.6%) and immunodiagnostic only in 1 (2.3%) case.

CONCLUSION

A notable proportion of children with TB had subclinical disease. This highlights the importance of non-symptom-based TB case finding in exposed children and refugees from high-TB-prevalence settings. TB screening in these asymptomatic children should therefore include a combination of immunodiagnostic testing and imaging followed by culture and molecular testing.

Computer-aided interpretation of chest radiography reveals the spectrum of tuberculosis in rural South Africa

Computer-aided digital chest radiograph interpretation (CAD) can facilitate high-throughput screening for tuberculosis (TB), but its use in population-based active case-finding programs has been limited. In an HIV-endemic area in rural South Africa, we used a CAD algorithm (CAD4TBv5) to interpret digital chest x-rays (CXR) as part of a mobile health screening effort. Participants with TB symptoms or CAD4TBv5 score above the triaging threshold were referred for microbiological sputum assessment. During an initial pilot phase, a low CAD4TBv5 triaging threshold of 25 was selected to maximize TB case finding. We report the performance of CAD4TBv5 in screening 9,914 participants, 99 (1.0%) of whom were found to have microbiologically proven TB. CAD4TBv5 was able to identify TB cases at the same sensitivity but lower specificity as a blinded radiologist, whereas the next generation of the algorithm (CAD4TBv6) achieved comparable sensitivity and specificity to the radiologist. The CXRs of people with microbiologically confirmed TB spanned a range of lung field abnormality, including 19 (19.2%) cases deemed normal by the radiologist. HIV serostatus did not impact CAD4TB's performance. Notably, 78.8% of the TB cases identified during this population-based survey were asymptomatic and therefore triaged for sputum collection on the basis of CAD4TBv5 score alone. While CAD4TBv6 has the potential to replace radiologists for triaging CXRs in TB prevalence surveys, population-specific piloting is necessary to set the appropriate triaging thresholds. Further work on image analysis strategies is needed to identify radiologically subtle active TB.