Prevalence and Risk Factors of Subclinical Tuberculosis in a Low-Incidence Setting in China

Knowledge and Prevalence of Latent Tuberculosis Infection: A Feasibility and Pilot Study in a Primary Healthcare Setting in Rural Eastern Cape, South Africa

Latent tuberculosis infection (LTBI) remains a significant global health concern, particularly in regions with high tuberculosis (TB) prevalence, such as South Africa. This pilot study aimed to evaluate the prevalence of LTBI and assess patient knowledge about the condition in a primary healthcare clinic in rural Eastern Cape, South Africa. A cross-sectional design was used, and convenience sampling recruited outpatients aged 18 years and older with no prior history of TB. Blood samples were analyzed using the QuantiFERON-TB Gold assay to determine LTBI status, and a survey assessed patient knowledge of LTBI. Strong positive correlations were observed between what patients understand by the term LTBI and how LTBI differs from TB (0.70), what patients understand by the term LTBI and the risk factors for developing LTBI (0.70), how LTBI differs from TB and the risk factors for developing LTBI (0.78), and how LTBI differs from TB and the recommended treatments for LTBI (0.79), indicating overlap in understanding. In contrast, there were negative correlations between if patients had ever heard of latent LTBI before and their understanding of the term LTBI (-0.25), the risk factors for developing LTBI (-0.22), LTBI progressing to active TB (-0.27), and the recommended treatments for LTBI (-0.27). This divergence points to different dimensions of patient knowledge and awareness. Age, gender, occupation, comorbidities, and HIV status showed varying LTBI positivity trends. Among younger patients aged 20-29, 15.4% tested positive, while the 30-39 group showed a nearly equal split between positive (48.1%) and negative cases. A higher positivity rate was seen in females (39.1%) compared to males (31.6%). Unemployed individuals had higher positivity rates, suggesting socioeconomic factors' influence. Comorbidities, especially hypertension, diabetes, and asthma, correlated with higher LTBI positivity among females, but this was less evident in males. HIV-positive patients had a higher LTBI-negative rate compared to HIV-negative patients. A logistic regression model (accuracy 70%) identified demographic and health factors predicting LTBI outcomes, with comorbidities, particularly hypertension and diabetes, significantly increasing the likelihood of LTBI positivity. These findings suggest that demographic and health factors, including age, gender, occupation, comorbidities, and HIV status, may predict LTBI positivity.

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.

Characteristics of smear-positive pulmonary tuberculosis with normal chest radiographic findings during a tuberculosis outbreak in northeast Malaysia: A cross-sectional study

Introduction

Tuberculosis (TB) remains a highly prevalent disease in Malaysia. Early identification using cost-effective methods such as chest radiography can reduce the health burden of a TB epidemic. However, normal chest radiographic findings are common. This study aimed to evaluate the characteristics of smear-positive pulmonary TB with normal chest radiographic findings during an outbreak.

Methods

A cross-sectional study was conducted by reviewing the medical records of 56 pulmonary TB cases registered at Kodiang Health Clinic from April to October 2022. Smear-negative and extrapulmonary TB cases were excluded. Relevant information was extracted from the medical records and recorded in a case report form for data management and analysis.

Results

Approximately 60.7% of the cases had symptoms lasting >2 weeks, and 89.3% showed abnormal findings upon clinical examination. Additionally, 73.2% had sputum acid-fast bacilli counts of ≥1+, and the sputum Mycobacterium tuberculosis culture and sensitivity test findings were positive in 82.1% of the cases. The proportion of smear-positive pulmonary TB with normal chest radiographic findings was 42.9%. The factors associated with smear-positive pulmonary TB with normal chest radiographic findings included being under 18 years old (P=0.021), being a student (P=0.010), being single (P=0.012) and being asymptomatic (P=0.04).

Conclusion

Normal chest radiographic findings may lead to a misdiagnosis of smear-positive pulmonary TB, especially during an outbreak. Therefore, active case detection among close contacts with risk factors for normal radiographic findings should consider additional supportive tests.

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.

Pooled sputum testing by Xpert® MTB/RIF Ultra for active tuberculosis case finding among high-risk groups in a low-incidence area: a prospective study

BACKGROUND

Early detection and treatment of tuberculosis (TB) are of great importance to stop its spread. However, optimising the active case findingstrategy is critical to improving its feasibility in regions where TB is epidemic.

METHOD

The different pooled ratios between TB-positive and TB-negative sputum specimens were evaluated and a pooling ratio of 5:1 was used for the active case finding screening by Xpert MTB/RIF Ultra among high-risk groups in Beijing.

RESULTS

The sensitivity of pooling ratio at 5:1 was 97.5% (39/40). Between October 2022 and March 2023, among 17,681 participants, 1729 metthe active case finding criteria and were screened by 350 5:1 sputum pools by Xpert MTB/RIF Ultra. Four pools (1.1%) tested positive and were further confirmed as definite active TB cases. In our study population with high TB incidence (231/100,000), the cost for detection of individual patients was reduced by 77.4% at a 5:1 pooling ratio.

CONCLUSIONS

pooled sputum testing at a suitable ratio using Xpert MTB/RIF Ultra provides a rapid, efficient, and cost-effective method for active TB case finding among high-risk groups in a low-incidence area.

Characteristics of culture-negative subclinical pulmonary tuberculosis: a single-center observation

BACKGROUND

Little is known about culture-negative subclinical pulmonary tuberculosis (TB), and its diagnosis remains challenging. Therefore, this study aimed to identify the characteristics and the extent of disease associated with culture-negative subclinical pulmonary TB.

METHODS

This retrospective cohort study was conducted on immunocompetent individuals with subclinical pulmonary TB at a university hospital in Thailand from January 2014 to December 2019. Subclinical pulmonary TB was diagnosed based on the presence of radiographic abnormalities consistent with TB in the absence of TB symptoms. All subjects demonstrated significant improvement or resolution of radiographic abnormalities following the completion of treatment. At least two negative sputum cultures were needed to fulfill the definition of culture-negative pulmonary TB. Data were analyzed using univariate and multiple logistic regression analyses to determine the characteristics of those with culture-negative subclinical pulmonary TB compared to culture-positive ones.

RESULTS

Out of the 106 individuals identified with subclinical pulmonary TB, 84 met the criteria for inclusion in the analysis. The study found lower radiographic extent and increasing age were key attributes of culture-negative subclinical pulmonary TB. The odds ratios (95% confidence interval) were 7.18 (1.76 to 29.35) and 1.07 (1.01 to 1.13), respectively. They tend to have lower rates of bilateral involvement in both chest x-ray (8.5% vs. 32.0%, p=0.006) and computed tomography (15.4% vs. 42.9%, p=0.035). However, no other specific radiographic findings were identified.

CONCLUSIONS

People with culture-negative subclinical pulmonary TB were likely to have less radiographic -severity, reflecting early disease. Nevertheless, no radiographic patterns, except for unilaterality, were related to culture-negative subclinical pulmonary TB.

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.

Insidious transmission of Mycobacterium tuberculosis in Ordos, China: a molecular epidemiology study

BACKGROUND

In this study, we conducted this population-based study to evaluate the genetic diversity and clustering rate of Mycobacterium tuberculosis (MTB) strains using the whole-genome sequencing (WGS), to better understand its transmission in Ordos.

METHODS

All patients with culture-positive TB notified in Ordos from January 2021 to December 2022 were recruited. WGS was performed to analyze single-nucleotide polymorphism (SNP) and to identify genotypic drug susceptibilities of MTB isolates.

RESULTS

Overall, a total of 186 patients were included in the present study, of whom 35 (18.8%) had no symptoms suggestive of active TB. Lineage 2 was the predominant MTB sublineage, accounting for 186 of isolates tested. When the pairwise SNP difference ≤ 12 was used as the cutoff for WGS-based clusters, we identified 17 genotypic clusters, and 38 isolates belonged to these 17 clusters, resulting in a clustering rate of 20.4%. The Beijing genotype was an independent factor associating with genomic-clustering (adjusted OR 4.219, 95% CI 0.962-18.502). The overall sensitivity on WGS-based resistance prediction was 85.7% for rifampicin, 73.1% for isoniazid, 60.0% for Ethambutol, 72.7% for streptomycin, and 72.7% for fluoroquinolones.

CONCLUSION

To conclude, the present study demonstrates the extensive recent transmission of Beijing genotype strains in the community of Ordos. The failure to provide a comprehensive pattern of transmission indicated the missed diagnosis of active TB within the community. A substantial proportion of subclinical TB cases are recognized in the bacteria-positive cases, emphasizing that we must interrupt transmission by finding people with active TB before they infect others.

Characteristics of subclinical tuberculosis compared to active symptomatic tuberculosis using nationwide registry cohort in Korea: prospective cohort study

Objective

The clinical manifestations of tuberculosis (TB) range from asymptomatic to disseminated depending on the microbiological and immunological status, making the diagnosis challenging. To improve our understanding of the disease progression mechanism, we aimed to identify the characteristics of subclinical TB and important predictors of symptom development.

Methods

From July 2018 to June 2019, we systemically collected data from the National Surveillance System of South Korea on patients with pulmonary TB, and compared the characteristics of subclinical and active symptomatic TB patients.

Results

A total of 4,636 patients with pulmonary TB were included, and the prevalence of subclinical TB was 37.1% (1,720/4,636). In subclinical TB patients, the positivity rates of acid-fast bacilli (AFB) smear and culture were 16.2 and 50.2%, respectively. Subclinical TB patients were younger (55.6 ± 19.2 vs. 60.7 ± 19.5, P < 0.001), had a higher body mass index (21.7 ± 3.1 vs. 21.0 ± 3.5, P < 0.001), less under Medicaid support, and had lower rates of chronic lung disease, AFB smear and culture positivity, and bilateral disease. Regarding the characteristic differences of individual TB-related symptoms, age was positively associated with dyspnoea and general weakness but negatively associated with chest pain, haemoptysis, and weight loss. Male patients were more prone to weight loss. Chronic lung disease was related to symptoms including cough/phlegm, dyspnoea, and haemoptysis, while autoimmune diseases were associated with fever and weight loss.

Conclusions

The development of TB-related symptoms was associated with microbiological burden and clinical characteristics including underlying comorbidities, which should be evaluated carefully.

Accuracy of Xpert® MTB/RIF Ultra test for posterior oropharyngeal saliva for the diagnosis of paucibacillary pulmonary tuberculosis: a prospective multicenter study

BACKGROUND

Posterior oropharyngeal saliva (POS) is increasingly recognized as an alternative specimen for detecting respiratory pathogens. The accuracy of Xpert® MTB/RIF Ultra (X-Ultra), when performed on POS obtained from patients with paucibacillary pulmonary tuberculosis (TB) is unclear.

METHODS

We consecutively recruited adults with symptoms suggestive of pulmonary TB who were negative by both smear microscopy and Xpert MTB/RIF (X-Classic). Each participant was required to provide one bronchoalveolar lavage fluid (BALF) and one POS specimen, respectively. Diagnostic performances of X-Ultra and X-Classic on POS were compared against clinical and mycobacterial reference standards.

FINDINGS

686 participants meeting inclusion criteria were consecutively enrolled into the study. The overall diagnostic sensitivities of X-Ultra and X-Classic on POS samples were 78.9% [95% confidence interval (CI): 72.8-83.8] and 56.4% (95% CI: 49.7-62.9), respectively; the specificities were 96.6% (95% CI: 94.3-98.1) for X-Ultra and 97.6 (95CI: 95.5-98.8) for X-Classic in POS specimens. Notably, the sensitivity of X-Ultra on POS was as sensitive as X-Classic on BALF against microbiological reference standard (78.9% VS 73.1%). Against clinical diagnosis as a reference standard, the sensitivities of X-Ultra and X-Classic on POS were 55.9% (95% CI: 50.5-61.2; 193/345) and 40.0% (95% CI: 34.8-45.4; 138/345), respectively. The risk of negative results with POS was dramatically increased with decreasing bacterial loads.

CONCLUSIONS

The testing of POS using X-Ultra shows promise as a tool to identify patients with paucibacillary TB. Considering that bronchoscopy is a semi-invasive procedure, POS testing ahead of bronchoscopy, may decrease the need for bronchoscopic procedures, and the cost of care.

Prevalence of subclinical pulmonary tuberculosis and its association with HIV in household contacts of index tuberculosis patients in two South African provinces: a secondary, cross-sectional analysis of a cluster-randomised trial

Background

People with subclinical tuberculosis (TB) have microbiological evidence of disease caused by Mycobacterium tuberculosis, but either do not have or do not report TB symptoms. The relationship between human immunodeficiency virus (HIV) and subclinical TB is not yet well understood. We estimated the prevalence of subclinical pulmonary TB in household contacts of index TB patients in two South African provinces, and how this differed by HIV status.

Methods

This was a cross-sectional, secondary analysis of baseline data from the intervention arm of a household cluster randomised trial. Prevalence of subclinical TB was measured as the number of household contacts aged ≥ 5 years who had positive sputum TB microscopy, culture or nucleic acid amplification test (Xpert MTB/Rif or Xpert Ultra) results on a single sputum specimen and who did not report current cough, fever, weight loss or night sweats on direct questioning. Regression analysis was used to calculate odds ratios (OR) and 95% confidence intervals (CI) for the association between HIV status and subclinical TB; adjusting for province, sex and age in household contacts; and HIV status in index patients.

Results

Amongst household contacts, microbiologically confirmed prevalent subclinical TB was over twice as common as symptomatic TB disease (48/2077, 2.3%, 95% CI 1.7-3.1% compared to 20/2077, 1.0%, 95% CI 0.6-1.5%). Subclinical TB prevalence was higher in people living with HIV (15/377, 4.0%, 95% CI 2.2-6.5%) compared to those who were HIV-negative (33/1696, 1.9%, 95% CI 1.3-2.7%; p = 0.018). In regression analysis, living with HIV (377/2077, 18.2%) was associated with a two-fold increase in prevalent subclinical TB with 95% confidence intervals consistent with no association through to a four-fold increase (adjusted OR 2.00, 95% CI 0.99-4.01, p = 0.052). Living with HIV was associated with a five-fold increase in prevalent symptomatic TB (adjusted OR 5.05, 95% CI 2.22-11.59, p < 0.001).

Conclusions

Most (70.6%) pulmonary TB diagnosed in household contacts in this setting was subclinical. Living with HIV was likely associated with prevalent subclinical TB and was associated with prevalent symptomatic TB. Universal sputum testing with sensitive assays improves early TB diagnosis in subclinical household contacts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s44263-023-00022-5.

Clinical assistant decision-making model of tuberculosis based on electronic health records

BACKGROUND

Tuberculosis is a dangerous infectious disease with the largest number of reported cases in China every year. Preventing missed diagnosis has an important impact on the prevention, treatment, and recovery of tuberculosis. The earliest pulmonary tuberculosis prediction models mainly used traditional image data combined with neural network models. However, a single data source tends to miss important information, such as primary symptoms and laboratory test results, that is available in multi-source data like medical records and tests. In this study, we propose a multi-stream integrated pulmonary tuberculosis diagnosis model based on structured and unstructured multi-source data from electronic health records. With the limited number of lung specialists and the high prevalence of tuberculosis, the application of this auxiliary diagnosis model can make substantial contributions to clinical settings.

METHODS

The subjects were patients at the respiratory department and infectious cases department of a large comprehensive hospital in China between 2015 to 2020. A total of 95,294 medical records were selected through a quality control process. Each record contains structured and unstructured data. First, numerical expressions of features for structured data were created. Then, feature engineering was performed through decision tree model, random forest, and GBDT. Features were included in the feature exclusion set as per their weights in descending order. When the importance of the set was higher than 0.7, this process was concluded. Finally, the contained features were used for model training. In addition, the unstructured free-text data was segmented at the character level and input into the model after indexing. Tuberculosis prediction was conducted through a multi-stream integration tuberculosis diagnosis model (MSI-PTDM), and the evaluation indices of accuracy, AUC, sensitivity, and specificity were compared against the prediction results of XGBoost, Text-CNN, Random Forest, SVM, and so on.

RESULTS

Through a variety of characteristic engineering methods, 20 characteristic factors, such as main complaint hemoptysis, cough, and test erythrocyte sedimentation rate, were selected, and the influencing factors were analyzed using the Chinese diagnostic standard of pulmonary tuberculosis. The area under the curve values for MSI-PTDM, XGBoost, Text-CNN, RF, and SVM were 0.9858, 0.9571, 0.9486, 0.9428, and 0.9429, respectively. The sensitivity, specificity, and accuracy of MSI-PTDM were 93.18%, 96.96%, and 96.96%, respectively. The MSI-PTDM prediction model was installed at a doctor workstation and operated in a real clinic environment for 4 months. A total of 692,949 patients were monitored, including 484 patients with confirmed pulmonary tuberculosis. The model predicted 440 cases of pulmonary tuberculosis. The positive sample recognition rate was 90.91%, the false-positive rate was 9.09%, the negative sample recognition rate was 96.17%, and the false-negative rate was 3.83%.

CONCLUSIONS

MSI-PTDM can process sparse data, dense data, and unstructured text data concurrently. The model adds a feature domain vector embedding the medical sparse features, and the single-valued sparse vectors are represented by multi-dimensional dense hidden vectors, which not only enhances the feature expression but also alleviates the side effects of sparsity on the model training. However, there may be information loss when features are extracted from text, and adding the processing of original unstructured text makes up for the error within the above process to a certain extent, so that the model can learn data more comprehensively and effectively. In addition, MSI-PTDM also allows interaction between features, considers the combination effect between patient features, adds more complex nonlinear calculation considerations, and improves the learning ability of the model. It has been verified using a test set and via deployment within an actual outpatient environment.

Tuberculosis in pregnancy

Due to COVID-19 pandemic, the latest progress of the End Tuberculosis (TB) Strategy was far from optimal and services for TB needs to be quickly restored. Pregnancy is a unique opportunity to screen and manage TB, and it is an essential step in TB eradication. Early diagnosis and treatment for active disease can reduce maternal and neonatal morbidities and mortality. The more widespread utilization of newer rapid molecular assays with drug-susceptibility testing has significantly shortened the diagnostic process for active TB disease. First-line anti-TB drugs are proven to be safe in pregnancy. Management of latent TB infection (LTBI) during pregnancy is controversial, but puerperium is a period of increased susceptibility to progress to active disease. Extrapulmonary TB (EPTB), multidrug-resistant TB (MDR-TB) and HIV co-infection remain significant issues surrounding TB management during pregnancy and often require input from a multidisciplinary team including TB experts.

Association between depression or anxiety symptoms and immune-inflammatory characteristics in in-patients with tuberculosis: A cross-sectional study

BACKGROUND

Depression and anxiety are major psychological issues among patients with tuberculosis (TB) owing to chronic and complex treatments, have been reported to be closely correlated with immune and inflammation. However, the association of peripheral immune-inflammatory characteristics with depression/anxiety symptoms in in-patients with TB has rarely been reported.

METHODS

A cross-sectional study of 338 in-patients with TB from 3 hospitals in China were enrolled to investigate their depression and anxiety status by using the nine-item Patient Health Questionnaire (PHQ-9) and seven-item Generalized Anxiety Disorder Scale (GAD-7). Participants were divided into groups based on their PHQ-9 and GAD-7 scores, and differences in demography and immune-inflammatory characteristics were studied. Logistic analysis was performed to explore factors related to depression and anxiety symptoms.

RESULTS

Depression and anxiety prevalence among patients with TB was 47.9 and 42.6%, respectively. Furthermore, 38.5% of patients reported a comorbidity of depression and anxiety symptoms. The counts of CD3, CD4, CD8, and lymphocytes decreased, whereas those of neutrophils, platelets, and peripheral blood cells and their derived indices increased among TB patients with depression or anxiety in comparison with those without symptoms (p < 0.05). In addition, increasing age, lower income (monthly income ≤ 3,000 yuan), divorced or widowed, drug resistance, and higher systemic immune inflammation index (SII) were significantly associated with depression or anxiety symptoms (p < 0.05).

CONCLUSION

Approximately half of the patients with TB suffered from depression or/and anxiety symptoms. Patients with depression or anxiety present worse cell immune status and stronger inflammatory responses compared to those without symptoms. We emphasized the importance of paying attention to the dysfunction of immune-inflammation process of TB patients with depression or anxiety symptoms. Especially, SII has a potential application value in guiding the evaluation of TB-related depression or anxiety owing to its easily accessibility and being economical.