A systematic review and meta-analysis of circulating serum and plasma microRNAs in TB diagnosis

BACKGROUND

Tuberculosis (TB) ranks as the second leading cause of death globally among all infectious diseases. This problem is likely due to the lack of biomarkers to differentiate the heterogeneous spectrum of infection. Therefore, the first step in solving this problem is to identify biomarkers to distinguish the different disease states of an individual and treat them accordingly. Circulating microRNA (miRNA) biomarkers are promising candidates for various diseases. In fact, we are yet to conceptualize how miRNA expression influences and predicts TB disease outcomes. Thus, this systematic review and meta-analysis aimed to assess the diagnostic efficacy of circulating miRNAs in Latent TB (LTB) and Active Pulmonary TB (PTB).

METHODS

Literature published between 2012 and 2021 was retrieved from PubMed, Web of Science, Cochrane, Scopus, Embase, and Google Scholar. Articles were screened based on inclusion and exclusion criteria, and their quality was assessed using the QUADAS-2 tool. Funnel plots and forest plots were generated to assess the likelihood of study bias and heterogeneity, respectively.

RESULTS

After the screening process, seven articles were selected for qualitative analysis. The study groups, which consisted of Healthy Control (HC) vs. TB and LTB vs. TB, exhibited an overall sensitivity of 81.9% (95% CI: 74.2, 87.7) and specificity of 68.3% (95% CI: 57.8, 77.2), respectively. However, our meta-analysis results highlighted two potentially valuable miRNA candidates, miR-197 and miR-144, for discriminating TB from HC. The miRNA signature model (miR197-3p, miR-let-7e-5p, and miR-223-3p) has also been shown to diagnose DR-TB with a sensitivity of 100%, but with a compromised specificity of only 75%.

CONCLUSION

miRNA biomarkers show a promising future for TB diagnostics. Further multicentre studies without biases are required to identify clinically valid biomarkers for different states of the TB disease spectrum.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (CRD42022302729).

TB specific intracellular cytokines production in Synovial liquid for diagnosis of tuberculous arthritis

INTRODUCTION

Skeletal tuberculosis (TB) accounts for about 10 to 35% of extrapulmonary cases and the knee is the most frequent site after the spine and hip. The diagnosis is difficult and largely clinical.

CASE PRESENTATION

This is a case of a young Pakistani man with a history of joint pain for about 4 years, who was diagnosed with chronic arthritis of the right knee. Microscopy of synovial fluid and conventional diagnostic tests to identify Mycobacterium tuberculosis were negative, while a non-classical method based on intracellular cytokine flow cytometry response of CD4 T-cells in synovial fluid helped us to address the diagnosis, which was subsequently confirmed by Polymerase Chain Reaction (PCR).

CONCLUSIONS

Thanks to an innovative immunological approach, supported by PCR for detection of M. tuberculosis DNA, we were able to diagnose tuberculous arthritis of the knee, which allowed prompt initiation of treatment to reduce morbidity and mortality.

The new Xpert Mycobacterium tuberculosis/rifampicin (MTB/Rif) Ultra assay in comparison to Xpert MTB/Rif assay for diagnosis of tuberculosis in children and adolescents

BACKGROUND

Microbiological diagnosis of pediatric tuberculosis (TB) using conventional microbiological techniques has been challenging due to paucibacillary nature of the disease. Molecular methods using cartridge-based tests like Xpert, have immensely improved diagnosis. A novel next-generation cartridge test, Xpert Ultra, incorporates two additional molecular targets and claims to have much lower detection limit. We attempted to compare the two techniques in presumptive pediatric TB patients.

OBJECTIVES

The aim of this study was to compare the diagnostic performance of Xpert MTB/Rif Ultra with Xpert MTB/Rif for the detection of pediatric TB.

STUDY DESIGN

This is an observational comparative analytical study.

METHODS

Children under 15 years of age with presumptive TB were enrolled. Appropriate specimens were obtained (sputum, induced sputum or gastric aspirate for suspected pulmonary TB, cerebrospinal fluid for suspected tubercular meningitis and pleural fluid for suspected tubercular pleural effusion), subjected to smear microscopy, mycobacterial culture, Xpert and Xpert ultra tests and other appropriate diagnostic investigations.

RESULTS

Out of 130 enrolled patients, 70 were diagnosed with TB using a composite reference standard (CRS). The overall sensitivity of Xpert was 64.29% [95% confidence interval (CI) 51.93-75.93%] and that of Xpert Ultra was 80% (95% CI 68.73-88.61%) with 100% overall specificity for both. The sensitivity of Xpert and Xpert Ultra in pulmonary specimens (n = 112) was 66.67% and 79.37% and in extrapulmonary specimens (n = 18) was 42.86% and 85.71%, respectively.

CONCLUSION

Our study found Ultra to be more sensitive than Xpert for the detection of Mycobacterium tuberculosis in children. Our findings support the use of Xpert Ultra as initial rapid molecular diagnostic test in children under evaluation for TB.

Optimization of the Simple One-Step Stool Processing Method to Diagnose Tuberculosis: Evaluation of Robustness and Stool Transport Conditions for Global Implementation

Stool is recommended as an alternative specimen for the diagnosis of tuberculosis (TB) in young children, as they cannot easily produce sputum. The Simple One-Step (SOS) stool processing method is a new and simple stool processing method for the detection of Mycobacterium tuberculosis (MTB) using Xpert MTB/RIF Ultra (Xpert-Ultra). We determined the robustness of the SOS stool processing method and stool specimen transport conditions in participants with confirmed TB. We processed stool using the standard protocol after simulated "transport," varying time, and temperature, and experimented with slightly modified processing steps. We included 2,963 Xpert-Ultra test results from 132 stool specimens of 47 TB participants, including 11 children aged <10 years. We compared Xpert-Ultra processing errors and MTB positivity rates between standard and modified procedures. Minor deviations from the standard SOS protocol did not significantly impact the Xpert-Ultra test outcomes. The rate of Xpert-Ultra processing errors significantly increased with noncold-chain transport, exposure of stool to sample reagent at room temperature or beyond 12 h, and adding >0.8 g of stool. We found that almost all steps in the current SOS stool processing method provide optimal Xpert-Ultra results but recommend an adjustment to use a wider range of stool amounts (0.3 to 0.8 g) than advised previously (0.8 g). With this adaptation, stool-based diagnosis of TB using the SOS stool processing method can be scaled-up. IMPORTANCE The manuscript will support the global implementation and scale-up of the SOS stool method in routine settings. It also provides important insights on the optimal stool transport conditions and robustness of the SOS method, which can be used for bacteriological diagnosis of TB in children at the lowest levels of the healthcare system, avoiding lengthy healthcare-seeking pathways and additional costs.

ESAT-6 a Major Virulence Factor of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb), the causative agent of human tuberculosis (TB), is one of the most successfully adapted human pathogens. Human-to-human transmission occurs at high rates through aerosols containing bacteria, but the pathogen evolved prior to the establishment of crowded populations. Mtb has developed a particular strategy to ensure persistence in the host until an opportunity for transmission arises. It has refined its lifestyle to obviate the need for virulence factors such as capsules, flagella, pili, or toxins to circumvent mucosal barriers. Instead, the pathogen uses host macrophages, where it establishes intracellular niches for its migration into the lung parenchyma and other tissues and for the induction of long-lived latency in granulomas. Finally, at the end of the infection cycle, Mtb induces necrotic cell death in macrophages to escape to the extracellular milieu and instructs a strong inflammatory response that is required for the progression from latency to disease and transmission. Common to all these events is ESAT-6, one of the major virulence factors secreted by the pathogen. This narrative review highlights the recent advances in understanding the role of ESAT-6 in hijacking macrophage function to establish successful infection and transmission and its use as a target for the development of diagnostic tools and vaccines.

Sensitivity of Various Case Detection Algorithms for Community-based Tuberculosis Screening

Using data from 388 people diagnosed with tuberculosis through a community-based screening program in Lima, Peru, we estimated that cough screening followed by sputum smear microscopy would have detected only 23% of cases found using an algorithm of radiographic screening followed by rapid nucleic acid amplification testing and clinical evaluation.

Development of a Clinical Prediction Score Including Monocyte-to-Lymphocyte Ratio to Inform Tuberculosis Treatment Among Children With HIV: A Multicountry Study

Background

Clinical pediatric tuberculosis (TB) diagnosis may lead to overdiagnosis particularly among children with human immunodeficiency virus (CHIV). We assessed the performance of monocyte-lymphocyte ratio (MLR) as a diagnostic biomarker and constructed a clinical prediction score to improve specificity of TB diagnosis in CHIV with limited access to microbiologic testing.

Methods

We pooled data from cohorts of children aged ≤13 years from Vietnam, Cameroon, and South Africa to validate the use of MLR ≥0.378, previously found as a TB diagnostic marker among CHIV. Using multivariable logistic regression, we created an internally validated prediction score for diagnosis of TB disease in CHIV.

Results

The combined cohort had 601 children (median age, 1.9 [interquartile range, 0.9-5.3] years); 300 (50%) children were male, and 283 (47%) had HIV. Elevated MLR ≥0.378 had sensitivity of 36% (95% confidence interval [CI], 23%-51%) and specificity of 79% (95% CI, 71%-86%) among CHIV in the validation cohort. A model using MLR ≥0.28, age ≥4 years, tuberculin skin testing ≥5 mm, TB contact history, fever >2 weeks, and chest radiograph suggestive of TB predicted active TB disease in CHIV with an area under the receiver operating characteristic curve of 0.85. A prediction score of ≥5 points had a sensitivity of 94% and specificity of 48% to identify confirmed TB, and a sensitivity of 82% and specificity of 48% to identify confirmed and unconfirmed TB groups combined.

Conclusions

Our score has comparable sensitivity and specificity to algorithms including microbiological testing and should enable clinicians to rapidly initiate TB treatment among CHIV when microbiological testing is unavailable.

Pre-Diagnosis Health Seeking Behaviors and Experiences Post-Diagnosis, among Men Diagnosed with Tuberculosis in a District of Gauteng Metropolitan City, South Africa: In-Depth Interviews

BACKGROUND

Tuberculosis remains the number one killer among infectious diseases in South Africa. The TB disease burden is said to be higher among males, 1.6 times more than females in 2018. Moreover, men are reported to have poor healthcare-seeking behaviors. Loss in social and physical functioning, including reduced sexual desires and changes in family life, have been reported following a TB diagnosis. This study explored the meaning that male TB patients attach to their TB diagnosis and impact of TB infection in their lives and those of the people living with them.

METHODS

This exploratory qualitative study was conducted among 25 participants recruited among male patients seeking TB care from two clinics in informal settlements of the city of Johannesburg. In-depth interviews with open-ended questions were conducted using an audio recorder for the collection of data. Data analysis was conducted on the NVivo version 12 software following an inductive thematic approach.

RESULTS

The ages of the participants ranged between 18 and 61 years. Most were unemployed, and only a few were married or in steady relationships. From the two emerging themes, pre-TB diagnosis health-seeking behaviors and post TB-diagnosis experiences, several subthemes were identified. For the former theme, the subthemes include, seeking help from community-based healers and self-medicating, waiting for some period to see if the alternative medicine or treatment worked, taking time to visit a healthcare facility, triggers to seek healthcare, and symptoms reported on presentation to the healthcare facility. The post-TB diagnosis subthemes include making sense of the TB diagnosis, context of disclosing the TB status, fear of social exclusion and experiences of stigma, support received during illness, life changes after TB infection and diagnosis, and lessons learned from the TB experience and future healthcare-seeking behavior.

CONCLUSION

Secrecy about the TB diagnosis indicates fear of social exclusion, and this could be due to the highly stigmatized nature of TB. Waiting to see if alternative medication worked, delayed the TB diagnosis, with consequent late initiation of the anti-TB treatment. The life changes experienced post-TB diagnosis affect the quality of life of the participants and their families. The study recommends that these issues be addressed as a priority.

Elevated IP-10 at the Protein and Gene Level Associates With Pulmonary TB

There is an urgent need for accurate and sensitive diagnostic tools that can overcome the current challenge to distinguish individuals with latent tuberculosis infection (LTBI) from individuals with active tuberculosis (TB). Recent literature has suggested that a group of cytokines may serve as biomarkers of TB disease progression. Using a multiplex ELISA, we quantified 27 circulatory markers present within the unstimulated plasma of individuals in Durban, South Africa who were healthy (n=20), LTBI (n=13), or had active TB (n=30). RT-qPCR was performed to measure gene expression of the cytokines of interest, using RNA isolated from healthy (n=20), LTBI (n=20), or active TB (n=30). We found that at the protein level, IL-1RA, IL-6, and IP-10 were significantly more abundant in participants with active TB (p< 0.05) compared to those with LTBI individuals. IP-10 also showed the strongest association with active TB compared to healthy and LTBI at mRNA level. Our data shows that these proteins may serve as biomarkers of TB at both the protein and gene level.

Tuberculosis in Adolescents in Bulgaria for a Three-Year Period: 2018-2020

Background: Each year, approximately two million adolescents and young adults in the world become infected with tuberculosis (TB). The problem is that the classification of the disease includes children in the age group 0−14 years and young adults aged 15 and over. The present study aims to analyze and compare the epidemiology and clinical presentation of TB in Bulgaria in the different age subgroups of childhood. Methods: A retrospective study was undertaken of the newly diagnosed children (n = 80) with TB treated onsite from January 2018 to December 2020 at the Multiprofile Hospital for Active Treatment of Pulmonary Diseases (“St. Sofia”). They were distributed into three age groups: aged 8−11 (prepuberty), aged 12−14 (younger adolescents), and aged above 15 (older adolescents). Results: A clear finding of the research indicated that adolescent children develop TB both as primary and secondary infections. In a large number of cases with the children under our care, we found enlarged intrathoracic lymph nodes as well as infiltrative changes in the lungs, i.e., we observed transitional forms. There were statistically significant differences between the age group >15 years old and each of the other two younger groups for diagnosis, the severity of intoxication, and BK spreading status. Conclusion: The course of tuberculosis in adolescence has its own specifics and differences between the three age groups in the current study.

Geographic accessibility to health facilities predicts uptake of community-based tuberculosis screening in an urban setting

Objectives:

Annually, more than 30% of individuals with tuberculosis (TB) remain undiagnosed. We aimed to assess whether geographic accessibility measures can identify neighborhoods that would benefit from TB screening services targeted toward closing the diagnosis gap.

Methods:

We used data from a community-based mobile TB screening program in Carabayllo district, Lima, Peru. We constructed four accessibility measures from the geographic center of neighborhoods to health facilities. We used logistic regression to assess the association between these measures and screening uptake in one’s residential neighborhood versus elsewhere, with quasi-information criterion values to assess the association.

Results:

We analyzed the screening locations for 25,000 Carabayllo residents from 49 neighborhoods. Pedestrian walk time was preferable to Euclidean distance or vehicular time in our models. For each additional 12 minutes walking time between the neighborhood and the health facility, the odds of residents using TB screening units located in their neighborhoods increased by 50% (95% CI: 26%–78%). Females had 9% (95% CI: 3%–16%) increased odds versus males of using a screening unit in their own neighborhood.

Conclusion:

Placing mobile TB screening units in neighborhoods with longer pedestrian time to access health facilities could benefit individuals who face more acute access barriers to health care.

Performance assessment of SD Bioline TB MPT64 assay for the diagnosis of Mycobacterium tuberculosis complex in Lagos, Nigeria

This study assessed the performance of SD Bioline MPT64 immunochromatographic test for the identification of Mycobacterium tuberculosis complex (MTBC) in Nigeria.A total of 157 mycobacterial isolates, comprising 120 (76.4%) MTBC (M. tuberculosis, 112; M. africanum, 5; M. bovis, 3) and 37 (23.6%) non-tuberculous mycobacteria (NTM) isolates from patients attending six DOTS centers in Lagos between June 2012 and July 2014 were analyzed. All the isolates were grown on Bactec MGIT960 liquid media and identified in parallel by the conventional method and MPT64 immunochromatographic test. Discrepant results were resolved using the line probe assay.The comorbid disease rates for HIV and type 2 diabetes were 20.9% and 8.2%, respectively. Compared to the conventional method, SD Bioline MPT64 identified 117 MTBC isolates correctly, producing a sensitivity of 97.5% (95% CI, 92.9-99.2) at a shorter growing median time of 11 days compared to 26 days by the conventional method. The three undetected MTBC were confirmed by the line probe assay to be M. tuberculosis strains. The test also identified all the NTM correctly producing a specificity of 100% (95% CI, 90.7-100).This study supports the integration of SD Bioline TB MPT64 antigen test into diagnostic workflow for rapid MTBC case identification in Nigeria.

New Developments and Insights in the Improvement of Mycobacterium tuberculosis Vaccines and Diagnostics Within the End TB Strategy

PURPOSE OF REVIEW

The alignment of sustainable development goals (SDGs) with the End Tuberculosis (TB) strategy provides an integrated roadmap to implement key approaches towards TB elimination. This review summarizes current social challenges for TB control, and yet, recent developments in TB diagnosis and vaccines in the context of the End TB strategy and SDGs to transform global health.

RECENT FINDINGS

Advances in non-sputum based TB biomarkers and whole genome sequencing technologies could revolutionize TB diagnostics. Moreover, synergistic novel technologies such as mRNA vaccination, nanovaccines and promising TB vaccine models are key promising developments for TB prevention and control.

SUMMARY

The End TB strategy depends on novel developments in point-of-care TB diagnostics and effective vaccines. However, despite outstanding technological developments in these fields, TB elimination will be unlikely achieved if TB social determinants are not fully addressed. Indeed, the End TB strategy and SDGs emphasize the importance of implementing sustainable universal health coverage and social protection.

Transcriptomic Profiles of Confirmed Pediatric Tuberculosis Patients and Household Contacts Identifies Active Tuberculosis, Infection, and Treatment Response Among Indian Children

BACKGROUND

Gene expression profiling is emerging as a tool for tuberculosis diagnosis and treatment response monitoring, but limited data specific to Indian children and incident tuberculosis infection (TBI) exist.

METHODS

Sixteen pediatric Indian tuberculosis cases were age- and sex-matched to 32 tuberculosis-exposed controls (13 developed incident TBI without subsequent active tuberculosis). Longitudinal samples were collected for ribonucleic acid sequencing. Differential expression analysis generated gene lists that identify tuberculosis diagnosis and tuberculosis treatment response. Data were compared with published gene lists. Population-specific risk score thresholds were calculated.

RESULTS

Seventy-one genes identified tuberculosis diagnosis and 25 treatment response. Within-group expression was partially explained by age, sex, and incident TBI. Transient changes in gene expression were identified after both infection and treatment. Application of 27 published gene lists to our data found variable performance for tuberculosis diagnosis (sensitivity 0.38-1.00, specificity 0.48-0.93) and treatment response (sensitivity 0.70-0.80, specificity 0.40-0.80). Our gene lists found similarly variable performance when applied to published datasets for diagnosis (sensitivity 0.56-0.85, specificity 0.50-0.85) and treatment response (sensitivity 0.49- 0.86, specificity 0.50-0.84).

CONCLUSIONS

Gene expression profiles among Indian children with confirmed tuberculosis were distinct from adult-derived gene lists, highlighting the importance of including distinct populations in differential gene expression models.

Expression levels of candidate circulating microRNAs in pediatric tuberculosis

Tuberculosis (TB) is a preventable and curable disease, but increased mortality and morbidity associated with TB is one of the leading causes of deaths worldwide. MicroRNAs (miRNAs) are small, non-coding RNAs known to regulate the host immune response against TB. We investigated the expression profile of candidate circulating miRNAs, which could be used as a blood biomarker for the effective diagnosis of pediatric tuberculosis. A cross-sectional comparative study was conducted, including 30 children with active-TB and 30 healthy controls (HC) in a tertiary care hospital in Puducherry. We used the SYBR green-based miScript qRT-PCR assay to analyze the expression levels of miRNAs in plasma. Further, we used the receiver operating characteristic curve (ROC) to evaluate the diagnostic value of miRNAs. Active-TB included 25 (83.3%) pulmonary TB and 5 (16.7%) extrapulmonary TB cases. We found a significant upregulation of miR-21, miR-29a, miR-31, miR-155, and downregulation of miR-146a in children with active-TB compared to HC. The ROC analysis showed an excellent diagnostic value of miRNAs as follows: miR‑31> miR‑155> miR‑146a with AUC of (95% CI) miRNAs 0.978, 0.953, and 0.903, respectively. Altered circulating miRNA expression levels could be involved in the dysregulation of the host immune response to TB. The ROC analysis indicated that miRNAs miR-31, miR-155 and miR-146a could be effective diagnostic biomarkers for the detection of active-TB in children.

Multi-parameter flow cytometry immunophenotyping distinguishes different stages of tuberculosis infection

OBJECTIVES

To identify new potential host biomarkers in blood to discriminate between active TB patients, uninfected (NoTBI) and latently infected contacts (LTBI).

METHODS

A blood cell count was performed to study parent leukocyte populations. Peripheral blood mononuclear cells (PBMCs) were isolated and a multi-parameter flow cytometry assay was conducted to study the distribution of basal and Mycobacterium tuberculosis (Mtb)-stimulated lymphocytes. Differences between groups and the area under the ROC curve (AUC) were investigated to assess the diagnostic accuracy.

RESULTS

Active TB patients presented higher Monocyte-to-lymphocyte and Neutrophil-to-lymphocyte ratios than LTBI and NoTBI contacts (p<0.0001; AUC>0.8). Lymphocyte subsets with differences (p >0.05; AUC >0.7) between active TB and both contact groups include the basal distribution of Th1/Th2 ratio, Th1-Th17, CD4⁺ Central Memory (T_CM) or MAIT cells. Expression of CD154 is increased in Mtb-activated CD4⁺ T_CM and Effector Memory T cells in active TB and LTBI compared to NoTBI. In CD4⁺T cells, expression of CD154 showed a higher accuracy than IFNγ to discriminate Mtb-specific activation.

CONCLUSIONS

We identified different cell subsets with potential use in tuberculosis diagnosis. Among them, distribution of CD4 T_CM cells and their expression of CD154 after Mtb-activation are the most promising candidates.

Outcomes of Community-Based Systematic Screening of Household Contacts of Patients with Multidrug-Resistant Tuberculosis in Myanmar

Screening of household contacts of patients with multidrug-resistant tuberculosis (MDR-TB) is a crucial active TB case-finding intervention. Before 2016, this intervention had not been implemented in Myanmar, a country with a high MDR-TB burden. In 2016, a community-based screening of household contacts of MDR-TB patients using a systematic TB-screening algorithm (symptom screening and chest radiography followed by sputum smear microscopy and Xpert-MTB/RIF assays) was implemented in 33 townships in Myanmar. We assessed the implementation of this intervention, how well the screening algorithm was followed, and the yield of active TB. Data collected between April 2016 and March 2017 were analyzed using logistic and log-binomial regression. Of 620 household contacts of 210 MDR-TB patients enrolled for screening, 620 (100%) underwent TB symptom screening and 505 (81%) underwent chest radiography. Of 240 (39%) symptomatic household contacts, 71 (30%) were not further screened according to the algorithm. Children aged <15 years were less likely to follow the algorithm. Twenty-four contacts were diagnosed with active TB, including two rifampicin- resistant cases (yield of active TB = 3.9%, 95% CI: 2.3%-6.5%). The highest yield was found among children aged <5 years (10.0%, 95% CI: 3.6%-24.7%). Household contact screening should be strengthened, continued, and scaled up for all MDR-TB patients in Myanmar.

Ultrasensitive electrochemical detection of Mycobacterium tuberculosis IS6110 fragment using gold nanoparticles decorated fullerene nanoparticles/nitrogen-doped graphene nanosheet as signal tags

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains the top fatal infection continuing to threat public health, and the present detection method for MTB is facing great challenges with the global TB burden. In response to this issue, a novel electrochemical DNA biosensor was developed for detecting the IS6110 fragment within MTB. For the first time, the nanohybrid of gold nanoparticles decorated fullerene nanoparticles/nitrogen-doped graphene nanosheet (Au-nano-C₆₀/NGS) directly served as a new signal tag to generate signal response without additional redox molecules and subsequently labeled with signal probes (SPs) to form tracer label to achieve signal amplification. Additionally, a biotin-avidin system was introduced to immobilize abundant capture probes (CPs), further improving the sensitivity of the proposed biosensor. After a typical sandwich hybridization, the proposed electrochemical DNA biosensor was incubated with tetraoctylammonium bromide (TOAB), which was used as a booster to induce the intrinsic redox activity of the tracer label, resulting in a discriminating current response. The proposed electrochemical DNA biosensor shows a broad linear range for MTB determination from 10 fM to 10 nM with a low limit of detection (LOD) of 3 fM. In addition, this proposed biosensor not only distinguishes mismatched DNA sequence, but also differentiates MTB from other pathogenic agents. More importantly, it has been preliminarily applied in clinical detection and displayed excellent ability to identify the PCR products of clinical samples. There is great potential for this developed method to be used in early diagnosis and monitor of TB.

Current Medical Management of Pulmonary Tuberculosis

Tuberculosis (TB) remains a common cause of infection and disease in much of the world. The majority of disease occurs from reactivation months or years after initial infection and most often involves the lungs. Sputum smears for acid-fast bacilli remain the initial diagnostic test but have limited sensitivity and specificity. Nucleic acid amplification tests are more sensitive and specific and can detect some mutations that cause drug resistance. Treatment of TB resistant to rifamycins alone or in combination with isoniazid and other drugs remains difficult and should be done in consultation with an expert in treating drug-resistant disease.

PERFORMANCE OF THE TUBERCULIN SKIN TEST IN MYCOBACTERIUM BOVIS-EXPOSED AND -UNEXPOSED AFRICAN LIONS (PANTHERA LEO)

Lion (Panthera leo) populations, classified as vulnerable under the International Union for Conservation of Nature red list of threatened species, are facing a variety of threats, including tuberculosis (TB) caused by Mycobacterium bovis. The lack of knowledge on pathogenesis and diagnosis of TB, the prolonged course of the disease, the existence of subclinical infection, and nonspecific clinical signs hamper management of TB in both free-ranging and captive lion populations. Early and accurate antemortem diagnosis of M. bovis infections is important for disease management. In this study, we investigate the suitability of the single intradermal cervical test (SICT), developed with free-ranging Kruger National Park (KNP) lions exposed to M. bovis, for use in other lion populations. Using the recommended interpretation, the specificity of the SICT was low in disease-free captive lions, leading to false-positive diagnoses in 54% of individuals in the present study. Alternative interpretations of the tuberculin skin test are proposed that significantly reduce false-positive diagnosis in the sampled captive lions without significantly affecting diagnoses in the KNP lions; these changes may facilitate screening for M. bovis infection regardless of the exposure status of the lion population being investigated.

A novel aptamer-based test for the rapid and accurate diagnosis of pleural tuberculosis

Pleural tuberculosis (pTB) is diagnosed by using a composite reference standard (CRS) since microbiological methods are grossly inadequate and an accurate diagnostic test remains an unmet need. The present study aimed to evaluate the utility of Mycobacterium tuberculosis (Mtb) antigen and DNA-based tests for pTB diagnosis. Patients were classified as 'Definite TB', 'Probable TB' and 'Non-TB' disease according to the CRS. We assessed the performance of in-house antigen detection assays, namely antibody-based Enzyme-Linked ImmunoSorbent Assay (ELISA) and aptamer-based Aptamer-Linked Immobilized Sorbent Assay (ALISA), targeting Mtb HspX protein and DNA-based tests namely, Xpert MTB/RIF and in-house devR-qPCR. ROC curves were generated for the combined group of 'Definite TB' and 'Probable TB' vs. 'Non-TB' disease group and cut-off values were derived to provide specificity of ≥98%. The sensitivity of ALISA was ∼93% vs. ∼24% of ELISA (p-value ≤0.0001). devR-qPCR exhibited a sensitivity of 50% vs. ∼22% of Xpert (p-value ≤0.01). This novel aptamer-based ALISA test surpasses the sensitivity criterion and matches the specificity requirement spelt out in the 'Target product profile' for extrapulmonary tuberculosis samples by Unitaid (Sensitivity ≥80%, Specificity 98%). The superior performance of the aptamer-based ALISA test indicates its translational potential to bridge the existing gap in pTB diagnosis.

Is bleach-sedimented smear microscopy an alternative to direct microscopy under programme conditions in India?

This cross-sectional multi-centric study compared the yield of and potential benefit for detecting smear-positive pulmonary tuberculosis (PTB) by bleach sedimentation (2% sodium-hypochlorite) versus direct microscopy under programme conditions in India. Among 3168 PTB suspects, 684 (21.6%) were detected by bleach sedimentation vs. 625 (19.7%) by direct microscopy, with a proportional overall agreement of 96% (κ = 0.88). While 594 patients were smear-positive with both methods, 31 patients detected by direct microscopy were missed and an additional 90 patients were detected by bleach sedimentation. Overall, bleach sedimentation increased the yield of smear-positive TB detection; however; it also increased the time to results.

Is physical access an impediment to tuberculosis diagnosis and treatment? A study from a rural district in North India

SETTING

All designated microscopy centres (DMCs) in Fatehgarh Sahib District, Punjab, India.

OBJECTIVE

To study the association of distance (physical access) to DMCs with loss to follow-up (LTFU) of presumptive tuberculosis (TB) cases while undergoing diagnostic sputum examination and failure to initiate treatment among smear-positive TB patients after diagnosis.

DESIGN

A cross-sectional, record-based study was undertaken to analyse patient records from routine laboratory registers in all DMCs from January to June 2012.

RESULT

More than 50% of presumptive TB cases had to travel >7 km to reach the DMC, totalling >28 km for two sputum examinations for the evaluation of an episode. The distance (>10 km) to the diagnostic facility was found to be significantly associated (P < 0.01), both with LTFU during diagnosis and with a delay (>7 days) in initiating treatment after diagnosis. There was a significant correlation (r = 0.7) between distance to the DMC and time to initiate treatment among smear-positive TB cases.

CONCLUSION

Distance from the nearest facility represents a significant risk for LTFU during diagnosis and delayed initiation of treatment after diagnosis. Further decentralisation of TB care services to the community level is required by expanding the network of DMCs or by organising sputum collection and transportation.

Screening for tuberculosis in pregnancy: do we need more than a symptom screen? Experience from western Kenya

OBJECTIVES

1) To explore the utility of tuberculosis (TB) symptom screening for symptoms of ≥2 weeks' duration in a routine setting, and 2) to compare differences in TB diagnosis between human immunodeficiency virus (HIV) infected and non-HIV-infected pregnant women in western Kenya.

DESIGN

Comparative cross-sectional study among pregnant women with known HIV status screened for TB from 2010 to 2012, in Eldoret, western Kenya.

RESULTS

Of 2983 participants, respectively 34 (1%), 1488 (50.5%) and 1461 (49.5%) had unknown, positive and negative HIV status. The median age was respectively 30 years (interquartile range [IQR] 26-35) and 26 years (IQR 24-31) in HIV-infected and non-infected participants. A positive symptom screen was found in respectively 8% (119/1488) and 5% (67/1461) of the HIV-infected and non-infected women. The median CD4 count at enrolment was 377 cells/μl (IQR 244-530) for HIV-infected women. One non-HIV-infected patient was sputum-positive. For HIV-infected women, TB was presumptively treated in 1% (16/1488) based on clinical symptoms and chest X-ray. Cumulatively, anti-tuberculosis treatment was offered to 0.6% (17/2949) of the participants.

CONCLUSION

This study does not seem to demonstrate the utility of TB symptom screening questionnaires in a routine setting among pregnant women, either HIV-infected or non-infected, in western Kenya.

Evaluation of antigen detection test (chromatographic immunoassay): potential to replace the antibody assay using purified 45-kDa protein for rapid diagnosis of tuberculosis

BACKGROUND

The current strategy for combating tuberculosis (TB) is based on the early detection and treatment of patients to halt transmission. The present study was conducted to evaluate the diagnostic potential of three Mycobacterium tuberculosis antigens, 45-kDa, A60, and sonicated MTB antigen (SmTB-Ag), as antibody/antigen detection methods for the rapid and accurate diagnosis of TB.

METHODS

The SmTB-Ag and 45-kDa antigens were purified and A60 antigen was supplied by Anda-Biologicals, France. The 45-kDa and A60 antigens (for antibody detection procedures) and SmTB-Ag (for antigen detection test) were tested in the same study subjects. ELISA and immunochromatographic (rapid) test were performed on 201 sputum and serum samples. Ninety-eight samples from TB patients and 103 samples from control individuals were studied.

RESULTS

The mean absorbance value of antibodies against 45-kDa antigen in the TB patients were (1.17 ± 0.44, CI 1.09-1.26), significantly higher than in the non-TB group, (0.8 ± 0.28, CI 0.74-0.85, P < 0.05). The sensitivities of tests using two antigens, 84% for the 45-kDa antigen and 65% for the A60 antigen, were lower than SmTB-Ag(93%). The rapid test yielded 93% sensitivity and 92% specificity.

CONCLUSION

Findings highlighted the importance of antigen detection as a diagnostic tool. The rapid test evaluated in this study may be useful for diagnosis of TB.

Measurement of ESAT6-induced IFNγ responses adjunct with CXCL9 increases the rate of diagnosis of active tuberculosis in an endemic region

Due to difficulties in direct diagnosis of Mycobacterium tuberculosis infection where site-specific specimens are not available, indirect methods of testing for infection are required. M. tuberculosis early secreted antigen target-6 (ESAT6) induced IFN-γ responses are specific, but do not differentiate between latent and active TB. The use of adjunct biomarkers for TB diagnosis has been proposed, such as the chemokines: CXCL9, CXCL10 and CCL2. ESAT6-induced IFN-γ CXCL9, CXCL10 and CCL2 was measured in whole blood cell supernatants of patients with pulmonary tuberculosis (PTB, n=36) and extrapulmonary TB (ETB, n=31) and compared with healthy endemic controls (EC, n=33). ESAT6-induced IFN-γ responses were positive in 32% of TB cases as compared with 15% of EC cases (p=0.048). ESAT6-induced CXCL9 responses were positive in 42% of TB cases and 15% of EC cases (p=0.006). ESAT6-induced-CXCL10 and -CCL2 responses did not discriminate between TB and EC groups. Measurement of IFN-γ or CXCL9 together diagnosed TB (53%) cases and was significant as compared with EC (p=0.014) cases. IFN-γ and CXCL10 together did not increase the number of TB cases diagnosed. Within TB groups, ESAT6-IFN-γ/CXCL9-based detection increased to 53% in PTB (p=0.031) and 54% in ETB (p=0.021), with comparable diagnosis in less severe extrapulmonary TB (L-ETB, 55%) and severe disseminated extrapulmonary TB (D-ETB, 50%). Given that 47% of TB cases remained undetected, this study shown that ESAT6-induced IFNγ and CXCL9 can support diagnosis, but must be supported by clinical correlation and other relevant investigations.

HIV co-infection with tuberculous and non-tuberculous mycobacteria in western Kenya: challenges in the diagnosis and management

BACKGROUND

Tuberculosis (TB) and HIV co-infections have a global prevalence with devastating morbidity and massive mortality, Sub-Saharan Africa being the worst hit.

OBJECTIVES

To evaluate the prevalence of TB-HIV co-infection and demonstrate the confusion caused by NTM and HIV/AIDS co-infection in TB diagnosis and treatment in western Kenya.

METHODS

In a cross-sectional study carried out at 10 hospitals in western Kenya, sputa from consenting 872 TB suspects underwent microscopy, and culture on Lowenstein-Jensen and Mycobacteria Growth Index Tube media. Isolates were identified using the Hain's GenoType(®) Mycobacterium CM and GenoType(®) Mycobacterium AS kits. A total of 695 participants were screened for HIV using Uni-Gold™ test and positives confirmed with the enzyme linked immunosorbent assay.

RESULTS

A total of 346 (39.7%) participants were diagnosed with TB. Out of the 346 TB cases, 263 (76%) were tested for HIV infection and 110 (41.8%) of these were sero-positive (co-infected). The female to male TB-HIV co-infection prevalence ratio (PR) was 1.35. This study reports isolation of non-tuberculous mycobacteria from TB suspects at a rate of 1.7%.

CONCLUSION

A high TB-HIV co-infection rate was observed in this study. The NTM disease could be misdiagnosed and treated as TB in western Kenya.