Tests for tuberculosis infection: landscape analysis

Impact of in-utero exposure to HIV and latent TB on infant humoral responses

Introduction

Latent tuberculosis infection (LTBI) is a common coinfection in people living with HIV (PWH). How LTBI and HIV exposure in utero influence the development of infant humoral immunity is not well characterized. To address this question, we assessed the relationship between maternal humoral responses in pregnant women with HIV or with HIV/LTBI on humoral responses in infants to BCG vaccination and TB acquisition.

Methods

Plasma samples were obtained from mother infant pairs during pregnancy (14-34 wks gestation) and in infants at 12 and 44 wks of age from the IMPAACT P1078 clinical trial. LTBI was established by Interferon gamma release assay (IGRA). Progression to active TB (ATB) disease was observed in 5 women at various times after giving birth. All infants were BCG vaccinated at birth and tested for IGRA at 44 weeks. Mtb (PPD, ESAT6/CFP10, Ag85A, LAM), HIV (GP120), and Influenza (HA) specific IgG, IgM, and IgA were measured in plasma samples using a bead based Luminex assay with Flexmap 3D.

Results

In maternal plasma there were no differences in Mtb-specific antibodies or viral antibodies in relation to maternal IGRA status. ATB progressors showed increases in Mtb-specific antibodies at diagnosis compared to study entry. However, when compared to the non-progressors at entry, progressors had higher levels of Ag85A IgG and reduced ESAT6/CFP10 IgG and LAM IgG, IgM, and IgA1. All infants showed a decrease in IgG to viral antigens (HIV GP120 and HA) from 12 to 44 weeks attributed to waning of maternally transferred antibody titers. However, Mtb-specific (PPD, ESAT6/CFP10, Ag85A, and LAM) IgG and IgM increased from 12 to 44 weeks. HIV and HA IgG levels in maternal and 12-week infant plasma were highly correlated, and ESAT6/CFP10 IgG and LAM IgG showed a relationship between maternal and infant Abs. Finally, in the subset of infants that tested IGRA positive at 44 weeks, we observed a trend for lower LAM IgM compared to IGRA- infants at 44 weeks.

Discussion

The results from our study raise the possibility that antibodies to LAM are associated with protection from progression to ATB and support further research into the development of humoral immunity against TB through infection or vaccination.

Evaluating the diagnostic accuracy of QIAreach QuantiFERON-TB compared to QuantiFERON-TB Gold Plus for tuberculosis: a systematic review and meta-analysis

Accurate tuberculosis (TB) diagnosis remains challenging, especially in resource-limited settings. This study aims to assess the diagnostic performance of the QIAreach QuantiFERON-TB (QFT) assay, with a specific focus on comparing its diagnostic performance with the QuantiFERON-TB Gold Plus (QFT-Plus). We systematically reviewed relevant individual studies on PubMed, Scopus, and Web of Science up to January 20, 2024. The focus was on evaluating the diagnostic parameters of the QIAreach QFT assay for TB infection, which included sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and concordance with the QFT-Plus assay. QIAreach QFT demonstrated strong diagnostic performance with a pooled sensitivity of 99% (95% CI 95-100%) and specificity of 94% (95% CI 85-97%). Additionally, it showed a PLR of 15.6 (95% CI 6.5-37.5) and NLR of 0.01 (95% CI 0-0.03). The pooled PPV and NPV were 88% (95% CI 70-98%) and 100% (95% CI 99-100%), respectively. Concordance analysis with QFT-Plus revealed a pooled positive percent agreement of 98% (95% CI 88-100%) and pooled negative percent agreement of 91% (95% CI 81-97%), with a pooled overall percent agreement of 92% (95% CI 83-98). In conclusion, QIAreach QFT has shown promising diagnostic performance, with a strong concordance with QFT-Plus. However, further studies are needed to comprehensively evaluate its diagnostic performance in the context of TB infection.

Surveillance of close contacts of patients with infectious tuberculosis: a prospective cohort study

BACKGROUND

A long-term follow-up of close contacts to monitor their infection status is essential to formulate a promising screening strategy. The study aimed to assess the dynamics of tuberculosis (TB) infection using Interferon-γ release assay (IGRA) and determine risk factors associated with TB infection.

METHODS

Definite TB patients were interviewed and their household contacts were screened for TB infection by IGRA during 12-month longitudinal investigation.

RESULTS

We included in our analyses 184 household contacts of 92 index TB patients. 87 individuals (47.3%) in contact group progressed to TB infection, of whom 86 developed into IGRA positive within 24 weeks. Close contacts with a higher age and comorbidities are easier to exhibit TB infection. Analysis showed that risk factors for becoming IGRA-positive individuals included residence, older age, comorbidities, BCG scar and high bacterial load. Contacts with BCG scar had a lower IGRA-positive rate.

CONCLUSION

IGRA conversion generally occurs within 24 weeks after exposure. The TB transmission happens since subclinical TB stage and the presence of BCG scar is an independent protective factor reducing risk of TB infection among close contacts. Repeated IGRA tests are sensible to conducted among close contacts at 24 weeks after exposure to identify the IGRA-positive individuals.

Construction of novel multi-epitope-based diagnostic biomarker HP16118P and its application in the differential diagnosis of Mycobacterium tuberculosis latent infection

Tuberculosis (TB) is an infectious disease that significantly threatens human health. However, the differential diagnosis of latent tuberculosis infection (LTBI) and active tuberculosis (ATB) remains a challenge for clinicians in early detection and preventive intervention. In this study, we developed a novel biomarker named HP16118P, utilizing 16 helper T lymphocyte (HTL) epitopes, 11 cytotoxic T lymphocyte (CTL) epitopes, and 8 B cell epitopes identified from 15 antigens associated with LTBI-RD using the IEDB database. We analyzed the physicochemical properties, spatial structure, and immunological characteristics of HP16118P using various tools, which indicated that it is a hydrophilic and relatively stable alkaline protein. Furthermore, HP16118P exhibited good antigenicity and immunogenicity, while being non-toxic and non-allergenic, with the potential to induce immune responses. We observed that HP16118P can stimulate the production of high levels of IFN-γ+ T lymphocytes in individuals with ATB, LTBI, and health controls. IL-5 induced by HP16118P demonstrated potential in distinguishing LTBI individuals and ATB patients (p=0.0372, AUC=0.8214, 95% CI [0.5843 to 1.000]) with a sensitivity of 100% and specificity of 71.43%. Furthermore, we incorporated the GM-CSF, IL-23, IL-5, and MCP-3 induced by HP16118P into 15 machine learning algorithms to construct a model. It was found that the Quadratic discriminant analysis model exhibited the best diagnostic performance for discriminating between LTBI and ATB, with a sensitivity of 1.00, specificity of 0.86, and accuracy of 0.93. In summary, HP16118P has demonstrated strong antigenicity and immunogenicity, with the induction of GM-CSF, IL-23, IL-5, and MCP-3, suggesting their potential for the differential diagnosis of LTBI and ATB.

Integrating systemic immune-inflammation index, fibrinogen, and T-SPOT.TB for precision distinction of active pulmonary tuberculosis in the era of mycobacterial disease research

Background

The clinical challenge of differentiating suspected tuberculosis with positive T-SPOT.TB results persist. This study aims to investigate the utility of the Systemic Immune-Inflammation Index (SII), Fibrinogen, and T-SPOT.TB in distinguishing between active pulmonary tuberculosis (PTB) and non-tuberculous lung diseases.

Methods

A retrospective analysis included 1,327 cases of active PTB with positive T-SPOT.TB results and 703 cases of non-tuberculous lung diseases from May 2016 to December 2020 at Meizhou People's Hospital. These were designated as the case group and the control group, respectively. The detection indicators of T-SPOT.TB: Early Secreted Antigenic Target 6 (ESAT-6), Culture Filtrate Protein 10 (CFP-10), as well as SII and Fibrinogen levels-were compared and analyzed for association and joint diagnostic value between the two groups.

Results

The case group showed higher values of ESAT-6, CFP-10, SII, and Fibrinogen compared to the control group (all p < 0.001). In the case group, SII and Fibrinogen did not correlate with ESAT-6 and CFP-10 (∣rs∣ all < 0.3) but were positively correlated with C-reactive protein (CRP; rs all > 0.3). SII and Fibrinogen values in smear-positive pulmonary tuberculosis were higher than in smear-negative cases (all p < 0.05). The optimal diagnostic thresholds for ESAT-6, CFP-10, SII, and Fibrinogen in differentiating between active PTB and non-tuberculous lung diseases were 21.50 SFCs/106 PBMC, 22.50 SFCs/106 PBMC, 2128.32, and 5.02 g/L, respectively. Regression logistic analysis showed that ESAT-6 < 21.5 (OR: 1.637, 95% CI: 1.311-2.043, p < 0.001), CFP-10 < 22.5 (OR: 3.918, 95% CI: 3.138-4.892, p = 0.025), SII < 2128.32 (OR: 0.763, 95% CI: 0.603-0.967, p < 0.001), and FIB < 5.02 (OR: 2.287, 95% CI: 1.865-2.806, p < 0.001) were independent risk factors for active PTB. The specificity for ESAT-6 + CFP-10, ESAT-6 + CFP-10 + SII, ESAT-6 + CFP-10 + FIB, and ESAT-6 + CFP-10 + SII + FIB was 82.5%, 83.2%, 95.8%, and 80.1%, respectively, while sensitivity was 52.6%, 53.0%, 55.8%, and 44.7%, and positive predictive values were 85.0%, 85.6%, 84.1%, and 89.6%, respectively.

Conclusion

SII and Fibrinogen are positively correlated with the degree of tuberculosis inflammation and the bacterial load of Mycobacterium tuberculosis. The combined detection of SII, Fibrinogen, and T-SPOT.TB is significant in distinguishing between active PTB with positive T-SPOT.TB results and non-tuberculous lung diseases.

Is the new tuberculous antigen-based skin test ready for use as an alternative to tuberculin skin test/interferon-gamma release assay for tuberculous diagnosis? A narrative review

In recent years, novel specific Mycobacteria tuberculous (TB) antigen-based skin test (TBST) has become available for clinical use. The mechanism of TBST is similar to the interferon-gamma release assay (IGRA), making it a potential alternative for identifying latent tuberculous infection (LTBI), especially in subjects with history of bacille Calmette-Guérin vaccination. Three different commercial brands have been developed in Denmark, Russia, and China. Clinical studies in the respective countries have shown promising sensitivity, specificity, and safety profile. Some studies attempted to address the applicability of TBST in specific subject groups but the discrepancy in defining LTBI and problematic methodologies undermine the generalisation of the results to other communities across the world. Limited cost-effectiveness studies for TBST have been conducted without exploring the health economics for preventing development of LTBI into active TB. Unlike IGRA, no clinical studies have addressed the correlation of TBST results (magnitude of induration) with the likelihood of development of active TB. Moreover, the different TBSTs are not widely available for clinical use. While TBST is a promising test to overcome the shortcomings of tuberculin skin tests, more clinical data are needed to support its general application globally for the diagnosis of LTBI.

Impact of active case-finding for tuberculosis on case-notifications in Blantyre, Malawi: A community-based cluster-randomised trial (SCALE)

Active case-finding (ACF) for tuberculosis can help find the "missing millions" with undiagnosed tuberculosis. In a cluster-randomised trial, we investigated impact of ACF on case-notifications in Blantyre, Malawi, where ACF has been intensively implemented following 2014 estimates of ~1,000 per 100,000 adults with undiagnosed TB. Following a pre-intervention prevalence survey (May 2019 to March 2020), constrained randomisation allocated neighbourhoods to either door-to-door ACF (sputum microscopy for reported cough >2 weeks) or standard-of-care (SOC). Implementation was interrupted by COVID-19. Cluster-level bacteriologically-confirmed case-notification rate (CNR) ratio within 91 days of ACF was our redefined primary outcome; comparison between arms used Poisson regression with random effects. Secondary outcomes were 91-day CNR ratios comparing all tuberculosis registrations and all non-ACF registrations. Interrupted time series (ITS) analysis of CNRs in the SOC arm examined prevalence survey impact. (ISRCTN11400592). 72 clusters served by 10 study-supported tuberculosis registration centres were randomised to ACF (261,244 adults, 58,944 person-years follow-up) or SOC (256,713 adults, 52,805 person-years). Of 1,192 ACF participants, 13 (1.09%) were smear-positive. Within 91 days, 113 (42 bacteriologically-confirmed) and 108 (33 bacteriologically-confirmed) tuberculosis patients were identified as ACF or SOC cluster residents, respectively. There was no difference by arm, with adjusted 91-day CNR ratios 1.12 (95% CI: 0.61-2.07) for bacteriologically-confirmed tuberculosis; 0.93 (95% CI: 0.68-1.28) for all tuberculosis registrations; and 0.86 (95%CI: 0.63-1.16) for non-ACF (routinely) diagnosed. Of 7,905 ACF and 7,992 SOC pre-intervention survey participants, 12 (0.15%) and 17 (0.21%), respectively, had culture/Xpert-confirmed tuberculosis. ITS analysis showed no survey impact on SOC CNRs. Despite residual undiagnosed tuberculosis of 150 per 100,000 population, there was no increase in tuberculosis notifications from this previously successful approach targeting symptomatic disease, likely due to previous TB ACF and rapid declines in TB burden. In such settings, future ACF should focus on targeted outreach and demand creation, alongside optimised facility-based screening. Trial Registration: ISRCTN11400592.

Diagnostic challenge of tuberculosis in systemic lupus erythematosus: a case report and literature review

Patients with systemic lupus erythematosus (SLE) are at increased risk of tuberculosis (TB) infection due to immune dysfunction and immunosuppressive therapy. We present a case study of a 40-year-old woman with systemic lupus erythematosus (SLE). Initially, she was diagnosed with a lupus flare based on her clinical symptoms and laboratory results. However, upon further investigation, positive polymerase-chain reaction results for M. tuberculosis in the cerebrospinal fluid and lung parenchymal changes on chest computed tomography scan were indicative of TB infection. There was initial uncertainty regarding whether TB had triggered a flare-up of SLE or if TB was merely mimicking the symptoms of a SLE flare-up. However, as increasing the prednisolone dose did not have a positive effect and the patient's condition improved significantly with anti-TB treatment alone, it became clearer that the deterioration observed upon admission was primarily due to TB progression rather than an SLE flare-up. Additionally, we review the current literature on TB and SLE, including risk factors, diagnostic challenges, and treatment considerations, highlighting the importance of considering TB infection in patients with SLE who present with overlapping manifestations. Prompt diagnosis and treatment are essential for improving outcomes in these patients.

Current status and future landscape of diagnosing tuberculosis infection

Interferon-γ release assays (IGRAs), such as QuantiFERON-TB Gold (QFT) or T-SPOT.TB, are frequently used as tools for the diagnosis of tuberculosis (TB) infection in the 21st century. QFT-Plus recently emerged as the fourth generation of QFT assays and has replaced QFT In-Tube. However, IGRAs have several problems regarding the identification of active, latent, and cured TB infection, and the time-consuming diagnosis of TB infection because of the overnight incubation of clinical specimens or complexity of measuring the level of interferon (IFN)-γ. To easily diagnose TB infection and quickly compare it with conventional IGRAs, many in vitro tests are developed based on assays other than enzyme-linked immunosorbent assay or enzyme-linked immunospot, such as the fluorescent lateral flow assay that requires less manual operation and a shorter time. Simplified versions of IGRAs are emerging, including QIAreach QuantiFERON-TB. On the other hand, to distinguish active TB from latent or cured TB infection, new immunodiagnostic biomarkers beyond IFN-γ are evaluated using QFT supernatants. While IFN-γ or IFN-γ-related chemokine such as IFN-γ induced protein 10 is a potential biomarker in patients with active TB, interleukin-2 or latency-associated antigen such as heparin-binding hemagglutinin may be useful to distinguish active TB from latent or cured TB infection. There are no potential biomarkers to fully distinguish the time-phase of TB infection at present. It is necessary to discover new immunodiagnostic biomarkers to facilitate decisions on treatment selection for active or latent TB infection.

Outlook for CRISPR-based tuberculosis assays now in their infancy

Tuberculosis (TB) remains a major underdiagnosed public health threat worldwide, being responsible for more than 10 million cases and one million deaths annually. TB diagnosis has become more rapid with the development and adoption of molecular tests, but remains challenging with traditional TB diagnosis, but there has not been a critical review of this area. Here, we systematically review these approaches to assess their diagnostic potential and issues with the development and clinical evaluation of proposed CRISPR-based TB assays. Based on these observations, we propose constructive suggestions to improve sample pretreatment, method development, clinical validation, and accessibility of these assays to streamline future assay development and validation studies.

Research tests for the diagnosis of tuberculosis infection

INTRODUCTION

Despite huge efforts, tuberculosis (TB) is still a major public health threat worldwide, it is estimated that a quarter of the global population is infected by Mycobacterium tuberculosis (Mtb). For controlling TB and reducing Mtb transmission it is fundamental to diagnose TB infection (TBI) as well as the progressors from TBI to disease to identify those requiring preventive therapy. At present, there is no gold standard test for TBI diagnosis although several new methodologies have been attempted.

AREAS COVERED

This review provides an update on the most recent approaches to develop reliable tests to diagnose TBI and progressors from infection to disease. Experimental tests are based on either the direct identification of Mtb (i.e., Mtb DNA upon host cells isolation; Mtb proteins or peptides) or host response (i.e., levels and quality of specific anti-Mtb antibodies; host blood transcriptome signatures).

EXPERT OPINION

The experimental tests described are very interesting. However, further investigation and randomized clinical trials are needed to improve the sensitivity and specificity of these new research-based tests. More reliable proofs-of-concept and simplification of technical procedures are necessary to develop new diagnostic tools for identifying TBI patients and those that will progress from infection to TB disease.

Pulmonary Tuberculosis in Children: A Forgotten Disease?

Even today, tuberculosis in childhood is a disease that is often undiagnosed and undertreated. In the absence of therapy with antituberculosis drugs, children in the first years of life have a high degree of severe forms and mortality. In these children, symptoms are often not very specific and can easily be confused with other diseases of bacterial, viral or fungal etiology, making diagnosis more difficult. Nevertheless, the introduction of new diagnostic techniques has allowed a more rapid identification of the infection. Indeed, Interferon gamma release assay (IGRA) is preferred to the Mantoux, albeit with obvious limitations in children aged <2 years. While the Xpert Mtb/RIF Ultra test is recommended as an initial diagnostic investigation of the gastric aspirate and/or stools in children with signs and symptoms of pulmonary tuberculosis. The drugs used in the treatment of susceptible and resistant TB are the same as those used in adults but doses and combinations are different in the pediatric age. In children, brief therapy is preferable in both the latent infection and the active disease, as a significant reduction in side effects is obtained.

Updated considerations in the diagnosis and management of tuberculosis infection and disease: integrating the latest evidence-based strategies

INTRODUCTION

Tuberculosis (TB) is a leading infectious cause of global morbidity and mortality, affecting nearly a quarter of the human population and accounting for over 10 million deaths each year. Over the past several decades, TB incidence and mortality have gradually declined, but 2021 marked a threatening reversal of this trend highlighting the importance of accurate diagnosis and effective treatment of all forms of TB.

AREAS COVERED

This review summarizes advances in TB diagnostics, addresses the treatment of people with TB infection and TB disease including recent evidence for treatment regimens for drug-susceptible and drug-resistant TB, and draws attention to special considerations in children and during pregnancy.

EXPERT OPINION

Improvements in diagnosis and management of TB have expanded the available options for TB control. Molecular testing has enhanced the detection of TB disease, but better diagnostics are still needed, particularly for certain populations such as children. Novel treatment regimens have shortened treatment and improved outcomes for people with TB. However, important questions remain regarding the optimal management of TB. Work must continue to ensure the potential of the latest developments is realized for all people affected by TB.

First evaluation of the performance of portable IGRA, QIAreach® QuantiFERON®-TB in intermediate TB incidence setting

Diagnosis and treatment of tuberculosis infection (TBI) are the core elements of tuberculosis elimination. Interferon gamma release assays have advantages over the tuberculin skin test, although their implementation in low-resource settings is challenging. The performance of a novel digital lateral flow assay QIAreach® QuantiFERON®-TB (QIAreach QFT) against the QuantiFERON®-TB Gold Plus (QFT-Plus) assay was evaluated in an intermediate incidence setting (Malaysia) according to the manufacturer's instructions. Individuals aged 4-82 years, who were candidates for TB infection screening for contact investigation were prospectively recruited. On 196 samples, the QIAreach-QFT showed a positive percent agreement (sensitivity) was 96.5% (CI 87.9-99.6%), a negative percent agreement (specificity) 94.2% (CI 88.4% to 97.6%) and an overall percentage of agreement was 94.9% (95% CI 90.6-97.6%) with a Cohen's κ of 0,88. Out of 196, 5.6% (11/196) samples gave an error result on QIAreach-QFT and 4.1% (8/196) samples gave indeterminate result on QFT-plus. The TTR for QIAreach QFT positive samples varied from 210-1200 seconds (20 min) and significantly correlated with IFN-γ level of QFT-Plus. QIAreach QFT could be considered an accurate and reliable point-of-need test to diagnose TB infection helping to achieve the WHO End TB programme goals even in decentralised settings where laboratory expertise and infrastructure may be limited.

Portable paper-based electrochemiluminescence test incorporating lateral-flow immunosensors for detection of interferon-γ levels

Tuberculosis (TB) poses a serious threat to human health and social development. Accurate diagnosis of mycobacterium tuberculosis infection plays a critical role in the prevention and treatment of tuberculosis. Interferon-γ (INF-γ) release assay (IGRA) is currently the only quantitative tuberculosis infection diagnosis method. An accurate, fast, and easily handled INF-γ detection method is the key to obtaining accurate results. Herein, we report a novel paper-based electrochemiluminescence (ECL) method based on lateral flow immunosensors that combines the easy handling characteristics of immunochromatography and the high sensitivity of electrochemiluminescence to detect IFN-γ. To our knowledge this is the first INF-γ detection method that combines immunochromatography with electrochemiluminescence. The paper-based ECL-LFI test consists of a sample pad, conjugation pad (with binding antibody IFN-γ-Ab1 conjugated with ruthenium tripyridine), detection pad (with capture antibody IFN-γ-Ab2 immobilized on nanospheres), absorbent pad, and electrode for signal activation. The ECL signal is obtained by cyclic voltammetry scanning at a speed of 0.1 V/s in the detection area of the paper-based ECL-LFI test. In our experiments, the paper-based ECL-LFI test exhibited a minimum detection limit of 2.57 pg/mL within 12 min, and a broad detection range of 2.57-5,000 pg/mL, with repeatability of 8.10% and stability of 4.97%. With the advantage of high accuracy and sensitivity, easy handling, and low user training requirements, this ECL-LFI test might be used as point-of-care testing (POCT) in the IGRA for tuberculosis diagnosis.

Predictive performance of interferon-gamma release assays and the tuberculin skin test for incident tuberculosis: an individual participant data meta-analysis

Background

Evidence on the comparative performance of purified protein derivative tuberculin skin tests (TST) and interferon-gamma release assays (IGRA) for predicting incident active tuberculosis (TB) remains conflicting. We conducted an individual participant data meta-analysis to directly compare the predictive performance for incident TB disease between TST and IGRA to inform policy.

Methods

We searched Medline and Embase from 1 January 2002 to 4 September 2020, and studies that were included in previous systematic reviews. We included prospective longitudinal studies in which participants received both TST and IGRA and estimated performance as hazard ratios (HR) for the development of all diagnoses of TB in participants with dichotomised positive test results compared to negative results, using different thresholds of positivity for TST. Secondary analyses included an evaluation of the impact of background TB incidence. We also estimated the sensitivity and specificity for predicting TB. We explored heterogeneity through pre-defined sub-group analyses (e.g. country-level TB incidence). Publication bias was assessed using funnel plots and Egger's test. This review is registered with PROSPERO, CRD42020205667.

Findings

We obtained data from 13 studies out of 40 that were considered eligible (N = 32,034 participants: 36% from countries with TB incidence rate ≥100 per 100,000 population). All reported data on TST and QuantiFERON Gold in-Tube (QFT-GIT). The point estimate for the TST was highest with higher cut-offs for positivity and particularly when stratified by bacillus Calmette-Guérin vaccine (BCG) status (15 mm if BCG vaccinated and 5 mm if not [TST5/15 mm]) at 2.88 (95% CI 1.69-4.90). The pooled HR for QFT-GIT was higher than for TST at 4.15 (95% CI 1.97-8.75). The difference was large in countries with TB incidence rate <100 per 100,000 population (HR 10.38, 95% CI 4.17-25.87 for QFT-GIT VS. HR 5.36, 95% CI 3.82-7.51 for TST5/15 mm) but much of this difference was driven by a single study (HR 5.13, 95% CI 3.58-7.35 for TST5/15 mm VS. 7.18, 95% CI 4.48-11.51 for QFT-GIT, when excluding the study, in which all 19 TB cases had positive QFT-GIT results). The comparative performance was similar in the higher burden countries (HR 1.61, 95% CI 1.23-2.10 for QFT-GIT VS. HR 1.72, 95% CI 0.98-3.01 for TST5/15 mm). The predictive performance of both tests was higher in countries with TB incidence rate <100 per 100,000 population. In the lower TB incidence countries, the specificity of TST (76% for TST5/15 mm) and QFT-GIT (74%) for predicting active TB approached the minimum World Health Organization target (≥75%), but the sensitivity was below the target of ≥75% (63% for TST5/15 mm and 65% for QFT-GIT). The absolute differences in positive and negative predictive values between TST15 mm and QFT-GIT were small (positive predictive values 2.74% VS. 2.46%; negative predictive values 99.42% VS. 99.52% in low-incidence countries). Egger's test did not show evidence of publication bias (0.74 for TST15 mm and p = 0.68 for QFT-GIT).

Interpretation

IGRA appears to have higher predictive performance than the TST in low TB incidence countries, but the difference was driven by a single study. Any advantage in clinical performance may be small, given the numerically similar positive and negative predictive values. Both IGRA and TST had lower performance in countries with high TB incidence. Test choice should be contextual and made considering operational and likely clinical impact of test results.

Funding

YH, IA, and MXR were supported by the National Institute for Health and Care Research (NIHR), United Kingdom (RP-PG-0217-20009). MQ was supported by the Medical Research Council [MC_UU_00004/07].

Challenges and the Way forward in Diagnosis and Treatment of Tuberculosis Infection

Globally, it is estimated that one-quarter of the world's population is latently infected with Mycobacterium tuberculosis (Mtb), also known as latent tuberculosis infection (LTBI). Recently, this condition has been referred to as tuberculosis infection (TBI), considering the dynamic spectrum of the infection, as 5-10% of the latently infected population will develop active TB (ATB). The chances of TBI development increase due to close contact with index TB patients. The emergence of multidrug-resistant TB (MDR-TB) and the risk of development of latent MDR-TB has further complicated the situation. Detection of TBI is challenging as the infected individual does not present symptoms. Currently, there is no gold standard for TBI diagnosis, and the only screening tests are tuberculin skin test (TST) and interferon gamma release assays (IGRAs). However, these tests have several limitations, including the inability to differentiate between ATB and TBI, false-positive results in BCG-vaccinated individuals (only for TST), false-negative results in children, elderly, and immunocompromised patients, and the inability to predict the progression to ATB, among others. Thus, new host markers and Mtb-specific antigens are being tested to develop new diagnostic methods. Besides screening, TBI therapy is a key intervention for TB control. However, the long-course treatment and associated side effects result in non-adherence to the treatment. Additionally, the latent MDR strains are not susceptible to the current TBI treatments, which add an additional challenge. This review discusses the current situation of TBI, as well as the challenges and efforts involved in its control.

A predictive model for early clinical diagnosis of spinal tuberculosis based on conventional laboratory indices: A multicenter real-world study

Background

Early diagnosis of spinal tuberculosis (STB) remains challenging. The aim of this study was to develop a predictive model for the early diagnosis of STB based on conventional laboratory indicators.

Method

The clinical data of patients with suspected STB in four hospitals were included, and variables were screened by Lasso regression. Eighty-five percent of the cases in the dataset were randomly selected as the training set, and the other 15% were selected as the validation set. The diagnostic prediction model was established by logistic regression in the training set, and the nomogram was drawn. The diagnostic performance of the model was verified in the validation set.

Result

A total of 206 patients were included in the study, including 105 patients with STB and 101 patients with NSTB. Twelve variables were screened by Lasso regression and modeled by logistic regression, and seven variables (TB.antibody, IGRAs, RBC, Mono%, RDW, AST, BUN) were finally included in the model. AUC of 0.9468 and 0.9188 in the training and validation cohort, respectively.

Conclusion

In this study, we developed a prediction model for the early diagnosis of STB which consisted of seven routine laboratory indicators.

Tuberculosis Infection in Children and Adolescents

The burden of tuberculosis (TB) in children and adolescents remains very significant. Several million children and adolescents are infected with TB each year worldwide following exposure to an infectious TB case and the risk of progression from TB infection to tuberculosis disease is higher in this group compared to adults. This review describes the risk factors for TB infection in children and adolescents. Following TB exposure, the risk of TB infection is determined by a combination of index case characteristics, contact features, and environmental determinants. We also present the recently recommended approaches to diagnose and treat TB infection as well as novel tests for infection. The tests for TB infection have limitations and diagnosis still relies on an indirect immunological assessment of cellular immune response to Mycobacterium tuberculosis antigens using immunodiagnostic testing. It is recommended that TB exposed children and adolescents and those living with HIV receive TB preventive treatment (TPT) to reduce the risk of progression to TB disease. Several TPT regimens of similar effectiveness and safety are now available and recommended by the World Health Organisation.

"It's too hard" - the management of latent TB in under-served populations in the UK: a qualitative study

BACKGROUND

UK national guidance recommends systematic screening for latent tuberculosis infection (LTBI) in under-served populations, including people experiencing homelessness and people who use drugs. This is not routinely implemented in the UK, and the reasons for this policy-practice mismatch remain underexplored.

METHODS

Semi-structured qualitative interviews were conducted with 19 healthcare professionals from across the UK. Participants were recruited using purposive sampling and snowballing, identifying individuals with excellent knowledge of their regions practice and policy of LTBI management. The interviews were conducted online, and were audio recorded, with transcripts thematically analysed using a two-stage inductive coding process to explore perceived barriers and enablers to LTBI screening.

RESULTS

Most participants had previous experience managing LTBI in under-served populations, but none were conducting systematic screening as per national guidance. We identified service provision challenges and low prioritisation of LTBI as the key explanatory themes driving this policy-practice mismatch. Lack of resource, and the complexity of clinical decision making were two key service level barriers. System and service inertia, and lack of cost effectiveness evidence led to LTBI being deprioritised. Service integration and promotion of WHO targets for TB elimination were highlighted as potential solutions.

CONCLUSION

Integrating LTBI testing and treatment with existing health services for under-served populations could improve feasibility and efficacy. Promotion of UK TB elimination goals and generation of regional evidence to support commissioning for LTBI care is vital. Without such a multi-pronged approach inertia is likely to persist and the zeitgeist will remain: "it's too hard".

Blue Skies research is essential for ending the Tuberculosis pandemic and advancing a personalized medicine approach for holistic management of Respiratory Tract infections

OBJECTIVES

Investments into 'Blue Skies' fundamental TB research in low- and middle-income countries (LMICs) have not been forthcoming. We highlight why blue skies research will be essential for achieving global TB control and eradicating TB.

METHODS

We review the historical background to early TB discovery research and give examples of where investments into basic science and fundamental 'blue skies research' are delivering novel data and approaches to advance diagnosis, management and holistic care for patients with active and latent TB infection.

FINDINGS

The COVID-19 pandemic has shown that making available adequate funding for priority investments into 'Blue skies research' to delineate scientific understanding of a new infectious diseases threat to global health security can lead to rapid development and rollout of new diagnostic platforms, treatments, and vaccines. Several advances in new TB diagnostics, new treatments and vaccine development are underpinned by basic science research.

CONCLUSIONS

Blue Skies research is required to pave the way for a personalized medicine approach for management of TB and other Respiratory Tract Infections and preventing long-term functional disability. Transfer of skills and resources by wealthier nations is required to empower researchers in LMICs countries to engage in and lead Blue Skies research.

Cost effectiveness analysis of single and sequential testing strategies for tuberculosis infection in adults living with HIV in the United States

Tuberculosis infection (TBI) frequently progresses to tuberculosis (TB) disease in people co-infected with human immunodeficiency virus (HIV). We examined the cost-effectiveness of single, sequential and no testing (total 12) strategies of TBI in HIV-infected people from the perspective of US healthcare provider. A decision-analytic model (20-year timeframe) was constructed to simulate TB-related outcomes: Direct medical cost and quality-adjusted life-years (QALYs). In the base-case analysis, the "confirm negative TST followed by QFT-Plus" strategy gained 0.1170 QALY at a total cost of USD3377. In the probabilistic sensitivity analysis of 10,000 Monte Carlo simulations, the probability of "confirm negative TST followed by QFT-Plus" to be accepted as cost-effective was the highest of all 12 strategies when the willingness-to-pay threshold exceeded 2340 USD/QALY. In conclusion, the strategy of "confirm negative TST followed by QFT-Plus" appears to be the preferred cost-effective option for TBI testing in HIV-infected people from the US healthcare provider's perspective.

Analysis of the diagnostic efficacy of the QuantiFERON-TB Gold In-Tube assay for preoperative differential diagnosis of spinal tuberculosis

Background

Differential diagnosis of spinal tuberculosis is important for the clinical management of patients, especially in populations with spinal bone destruction. There are few effective tools for preoperative differential diagnosis in these populations. The QuantiFERON-TB Gold In-Tube (QFT-GIT) test has good sensitivity and specificity for the diagnosis of tuberculosis, but its efficacy in preoperative diagnosis of spinal tuberculosis has rarely been investigated.

Method

A total of 123 consecutive patients with suspected spinal tuberculosis hospitalized from March 20, 2020, to April 10, 2022, were included, and the QFT-GIT test was performed on each patient. We retrospectively collected clinical data from these patients. A receiver operating characteristic (ROC) curve was plotted with the TB Ag-Nil values. The cutoff point was calculated from the ROC curve of 61 patients in the study cohort, and the diagnostic validity of the cutoff point was verified in a new cohort of 62 patients. The correlations between TB Ag-Nil values and other clinical characteristics of the patients were analyzed.

Results

Of the 123 patients included in the study, 51 had confirmed tuberculosis, and 72 had non-tuberculosis disease (AUC=0.866, 95% CI: 0.798-0.933, P&lt;0.0001). In patients with spinal tuberculosis, the QFT-GIT test sensitivity was 92.16% (95% CI: 80.25%-97.46%), and the specificity was 67.14% (95% CI: 54.77%-77.62%). The accuracy of diagnostic tests in the validation cohort increased from 77.42% to 80.65% when a new cutoff point was selected (1.58 IU/mL) from the ROC curve of the study cohort. The TB Ag-Nil values in tuberculosis patients were correlated with the duration of the patients’ disease (r=0.4148, P=0.0025).

Conclusion

The QFT-GIT test is an important test for preoperative differential diagnosis of spinal tuberculosis with high sensitivity but low specificity. The diagnostic efficacy of the QFT-GIT test can be significantly improved via application of a new threshold (1.58 IU/mL), and the intensity of the QFT-GIT test findings in spinal tuberculosis may be related to the duration of a patient’s disease.

Prediction of Th1 and Cytotoxic T Lymphocyte Epitopes of Mycobacterium tuberculosis and Evaluation of Their Potential in the Diagnosis of Tuberculosis in a Mouse Model and in Humans

Latent tuberculosis infection (LTBI) is the primary source of tuberculosis (TB) but there is no suitable detection method to distinguish LTBI from active tuberculosis (ATB). In this study, five antigens of Mycobacterium tuberculosis belonging to LTBI and regions of difference (RDs) were selected to predict Th1 and cytotoxic T lymphocyte (CTL) epitopes. The immunodominant Th1 and CTL peptides were identified in mouse models, and their performance in distinguishing LTBI from ATB was determined in mice and humans. Ten Th1 and ten CTL immunodominant peptides were predicted and synthesized in vitro. The enzyme-linked immunosorbent spot assay results showed that the combination of five Th1 peptides (area under the curve [AUC] = 1, P < 0.0001; sensitivity = 100% and specificity = 93.33%), the combination of seven CTL peptides (AUC = 1, P < 0.0001; 100 and 95.24%), and the combination of four peptide pools (AUC = 1, P < 0.0001; sensitivity = 100% and specificity = 91.67%) could significantly discriminate mice with LTBI from mice with ATB or uninfected controls (UCs). The combined peptides or peptide pools induced significantly different cytokine levels between the three groups, improving their ability to differentiate ATB from LTBI. Furthermore, it was found that pool 2 could distinguish patients with ATB from UCs (AUC = 0.6728, P = 0.0041; sensitivity = 72.58% and specificity = 59.46%). The combination of Th1 and CTL immunodominant peptides derived from LTBI-RD antigens might be a promising strategy for diagnosing ATB and LTBI in mice and patients with ATB and uninfected controls. IMPORTANCE Latent tuberculosis infection (LTBI) is a challenging problem in preventing, diagnosing, and treating tuberculosis (TB). The innate and adaptive immune responses are essential for eliminating or killing the mycobacteria. Antigen-presenting cells (APCs) present and display mycobacterium peptides on their surfaces, and recognition between T cells and APCs is based on some essential peptides rather than the full-length protein. Therefore, the selection of candidate antigens and the prediction and screening of potential immunodominant peptides have become a key to designing a new generation of TB diagnostic biomarkers. This study is the first to report that the combination of Th1 and CTL immunodominant peptides derived from LTBI-RD antigens can distinguish LTBI from active TB (ATB) in animals and ATB patients from uninfected individuals. These findings provide a novel insight for discovering potential biomarkers for the differential diagnosis of ATB and LTBI in the future.

Skin thickness affects the result of tuberculin skin test in systemic sclerosis

Background

Skin thickness is a prominent clinical feature of systemic sclerosis (SSc), but there is no consensus on the cut-off for a positive tuberculin skin test (TST) size and the limitation of the TST for a diagnosis of tuberculosis in SSc. We aimed to identify the cut-off size of an indurated TST and the sensitivity and specificity of the test for the diagnosis of tuberculosis in SSc patients.

Methods

A cross-sectional study of 168 adult Thai SSc patients was conducted. The TST was done using 0.1 ml of purified protein derivatives via intradermal injection. The test was interpreted 72 h after testing.

Results

The median age was 57.2 years. The majority (71.8%) had the diffuse cutaneous SSc subset. All the patients had a BCG vaccination at birth, and 17 (10.1%) had a tuberculosis infection. An indurated skin reaction size of 20 mm had the highest specificity for tuberculosis (99.3%: 95%CI 96.4–100) (ROC 0.53). The skin thickness—assessed using the modified Rodnan skin score (mRSS)—had a significant negative correlation with the reaction size (Rho -0.23; p = 0.003).

Conclusion

The TST is not sufficiently sensitive for detecting TB infection in SSc patients, albeit a skin induration of ≥ 15 mm indicates a high specificity for tuberculosis infection. A high mRSS resulted in a smaller skin reaction size when using the TST, which has limited utility as a diagnostic for tuberculosis among SSc patients with severe skin thickness.

The manuscript was presented as a poster presentation at the Annual European Congress of Rheumatology EULAR 2019 Madrid 12–15 June 2019. (Ann Rheum Dis. 2019;78(suppl 2): abstract FRI0347) http://dx.doi.org/10.1136/annrheumdis-2019-eular.1456

Supplementary Information

The online version contains supplementary material available at 10.1186/s41927-022-00278-8.

Biomarkers to identify Mycobacterium tuberculosis infection among borderline QuantiFERON results

BACKGROUND

Screening for tuberculosis (TB) infection often includes QuantiFERON-TB Gold Plus (QFT) testing. Previous studies showed that two-thirds of patients with negative QFT results just below the cut-off, so-called borderline test results, nevertheless had other evidence of TB infection. This study aimed to identify a biomarker profile by which borderline QFT results due to TB infection can be distinguished from random test variation.

METHODS

QFT supernatants of patients with a borderline (≥0.15 and <0.35 IU·mL-1), low-negative (<0.15 IU·mL-1) or positive (≥0.35 IU·mL-1) QFT result were collected in three hospitals. Bead-based multiplex assays were used to analyse 48 different cytokines, chemokines and growth factors. A prediction model was derived using LASSO regression and applied further to discriminate QFT-positive Mycobacterium tuberculosis-infected patients from borderline QFT patients and QFT-negative patients RESULTS: QFT samples of 195 patients were collected and analysed. Global testing revealed that the levels of 10 kDa interferon (IFN)-γ-induced protein (IP-10/CXCL10), monokine induced by IFN-γ (MIG/CXCL9) and interleukin-1 receptor antagonist in the antigen-stimulated tubes were each significantly higher in patients with a positive QFT result compared with low-negative QFT individuals (p<0.001). A prediction model based on IP-10 and MIG proved highly accurate in discriminating patients with a positive QFT (TB infection) from uninfected individuals with a low-negative QFT (sensitivity 1.00 (95% CI 0.79-1.00) and specificity 0.95 (95% CI 0.74-1.00)). This same model predicted TB infection in 68% of 87 patients with a borderline QFT result.

CONCLUSIONS

This study was able to classify borderline QFT results as likely infection-related or random. These findings support additional laboratory testing for either IP-10 or MIG following a borderline QFT result for individuals at increased risk of reactivation TB.

Are mRNA based transcriptomic signatures ready for diagnosing tuberculosis in the clinic? - A review of evidence and the technological landscape

Funding

Adaptive Immune Response to Mycobacterium abscessus Complex (MABSC) in Cystic Fibrosis and the Implications of Cross-Reactivity

Background

We aimed to characterise the adaptive immune response to Mycobacterium abscessus complex (MABSC) and its cross-reactivity with Mycobacterium avium complex (MAC) and Mycobacterium bovis (Bacille Calmette-Guérin, BCG) in cystic fibrosis (CF) patients and non-CF controls in terms of lymphocyte proliferation and immunophenotyping, cytokine production and anti-MABSC IgG plasma levels.

Methods

In this cross-sectional analysis, peripheral blood mononuclear cells (PBMC) from CF patients with MABSC (CF/MABSC, n=12), MAC infection history (CF/MAC, n=5), no NTM history (CF/NTM-, n=15), BCG-vaccinated (C/BCG+, n=9) and non-vaccinated controls (C/BCG-, n=8) were cultured for four days under stimulation with an in-house MABSC lysate and we used flow cytometry to assess lymphocyte proliferation (given by lymphoblast formation) and immunophenotypes. Cytokine production was assessed after overnight whole blood stimulation with the same lysate, and anti-MABSC IgG levels were measured in plasma from non-stimulated blood.

Results

All CF/MABSC patients had increased CD3+ and CD19+ lymphoblast formation upon PBMC stimulation with MABSC lysate. There was a higher rate of CD3+ than CD19+ lymphoblasts, predominance of CD4+ over CD8+ lymphoblasts, IFN-γ, TNF-α and IL-2 production, low production of the Th17-associated IL-17, and discrete or no production of Th2/B cell-associated cytokines soluble CD40 ligand (CD40L), IL-4 and IL-5, indicating a Th1-dominated phenotype and infection restricted to the lungs. A similar pattern was seen in C/BCG+ controls, and CF/MAC patients, pointing to cross-reactivity. MABSC-IgG levels were higher in CF/MABSC patients than in both control groups, but not CF/NTM- patients, most of whom also had CD3+ and/or CD19+ lymphoblast formation upon PBMC stimulation, indicating previous exposure, subclinical or latent infection with MABSC or other NTM.

Conclusion

The anti-MABSC immune response is Th1-skewed and underlines the cross-reactivity in the anti-mycobacterial immune response. The results, together with published clinical observations, indicate that BCG vaccination may cross-react against NTM in CF patients, and this should be investigated. Due to cross-reactivity, it would also be interesting to investigate whether a combination of MABSC-induced cytokine production by blood cells and anti-MABSC IgG measurement can be useful for identifying latent or subclinical infection both with MABSC and other NTM in CF patients.

Reimagining the status quo: How close are we to rapid sputum-free tuberculosis diagnostics for all?

Rapid, accurate, sputum-free tests for tuberculosis (TB) triage and confirmation are urgently needed to close the widening diagnostic gap. We summarise key technologies and review programmatic, systems, and resource issues that could affect the impact of diagnostics. Mid-to-early-stage technologies like artificial intelligence-based automated digital chest X-radiography and capillary blood point-of-care assays are particularly promising. Pitfalls in the diagnostic pipeline, included a lack of community-based tools. We outline how these technologies may complement one another within the context of the TB care cascade, help overturn current paradigms (eg, reducing syndromic triage reliance, permitting subclinical TB to be diagnosed), and expand options for extra-pulmonary TB. We review challenges such as the difficulty of detecting paucibacillary TB and the limitations of current reference standards, and discuss how researchers and developers can better design and evaluate assays to optimise programmatic uptake. Finally, we outline how leveraging the urgency and innovation applied to COVID-19 is critical to improving TB patients' diagnostic quality-of-care.

Clinical standards for the diagnosis, treatment and prevention of TB infection

BACKGROUND: Tuberculosis (TB) preventive therapy (TPT) decreases the risk of developing TB disease and its associated morbidity and mortality. The aim of these clinical standards is to guide the assessment, management of TB infection (TBI) and implementation of TPT.METHODS: A panel of global experts in the field of TB care was identified; 41 participated in a Delphi process. A 5-point Likert scale was used to score the initial standards. After rounds of revision, the document was approved with 100% agreement.RESULTS: Eight clinical standards were defined: Standard 1, all individuals belonging to at-risk groups for TB should undergo testing for TBI; Standard 2, all individual candidates for TPT (including caregivers of children) should undergo a counselling/health education session; Standard 3, testing for TBI: timing and test of choice should be optimised; Standard 4, TB disease should be excluded prior to initiation of TPT; Standard 5, all candidates for TPT should undergo a set of baseline examinations; Standard 6, all individuals initiating TPT should receive one of the recommended regimens; Standard 7, all individuals who have started TPT should be monitored; Standard 8, a TBI screening and testing register should be kept to inform the cascade of care.CONCLUSION: This is the first consensus-based set of Clinical Standards for TBI. This document guides clinicians, programme managers and public health officers in planning and implementing adequate measures to assess and manage TBI.

Know your tuberculosis epidemic-Is it time to add Mycobacterium tuberculosis immunoreactivity back into global surveillance?

Tuberculosis (TB) still causes 1.5 million deaths globally each year. Over recent decades, slow and uneven declines in TB incidence have resulted in a falling prevalence of TB disease, which increasingly concentrates in vulnerable populations. Falling prevalence, while welcome, poses new challenges for TB surveillance. Cross-sectional disease surveys require very large sample sizes to accurately estimate disease burden, and even more participants to detect trends over time or identify high-risk areas or populations, making them prohibitively resource-intensive. In the past, tuberculin skin surveys measuring Mycobacterium tuberculosis (Mtb) immunoreactivity were widely used to monitor TB epidemiology in high-incidence settings, but were limited by challenges with both delivering and interpreting the test. Here we argue that the shifting epidemiology of tuberculosis, and the development of new tests for Mtb infection, make it timely and important to revisit the strategy of TB surveillance based on infection or immunoreactivity. Mtb infection surveys carry their own operational challenges and fundamental questions, for example: around survey design and frequency; which groups should be included; how the prevalence of immunoreactivity in a population should be used to estimate force of infection; how individual results should be interpreted and managed; and how surveillance can be delivered efficiently and ethically. However, if these knowledge gaps are addressed, the relative feasibility and lower costs of Mtb infection surveillance offer a powerful and affordable opportunity to better "know your TB epidemic", understand trends, identify high-risk and underserved communities, and tailor public health responses to dynamic epidemiology.

Differential Diagnosis of Latent Tuberculosis Infection and Active Tuberculosis: A Key to a Successful Tuberculosis Control Strategy

As an ancient infectious disease, tuberculosis (TB) is still the leading cause of death from a single infectious agent worldwide. Latent TB infection (LTBI) has been recognized as the largest source of new TB cases and is one of the biggest obstacles to achieving the aim of the End TB Strategy. The latest data indicate that a considerable percentage of the population with LTBI and the lack of differential diagnosis between LTBI and active TB (aTB) may be potential reasons for the high TB morbidity and mortality in countries with high TB burdens. The tuberculin skin test (TST) has been used to diagnose TB for > 100 years, but it fails to distinguish patients with LTBI from those with aTB and people who have received Bacillus Calmette–Guérin vaccination. To overcome the limitations of TST, several new skin tests and interferon-gamma release assays have been developed, such as the Diaskintest, C-Tb skin test, EC-Test, and T-cell spot of the TB assay, QuantiFERON-TB Gold In-Tube, QuantiFERON-TB Gold-Plus, LIAISON QuantiFERON-TB Gold Plus test, and LIOFeron TB/LTBI. However, these methods cannot distinguish LTBI from aTB. To investigate the reasons why all these methods cannot distinguish LTBI from aTB, we have explained the concept and definition of LTBI and expounded on the immunological mechanism of LTBI in this review. In addition, we have outlined the research status, future directions, and challenges of LTBI differential diagnosis, including novel biomarkers derived from Mycobacterium tuberculosis and hosts, new models and algorithms, omics technologies, and microbiota.

Evaluation of a lateral-flow nanoparticle fluorescence assay for TB infection diagnosis

BACKGROUND:

Programmatic management of TB infection is a critical component of the WHO End TB Strategy. Interferon-gamma release assays (IGRAs) overcome some limitations of the tuberculin skin test, but implementation of IGRA testing in low-resource settings is challenging.

METHODS:

In this feasibility study, we evaluated performance of a novel digital lateral-flow assay, the QIAreach® QuantiFERON® TB (QIAreach-QFT) test, against the QuantiFERON®-TB Gold Plus (QFT-Plus) assay. A population with a mix of risk factors for TB infection (111 donors) were sampled over multiple days. A total of 207 individual blood samples were tested according to the manufacturer’s instructions.

RESULTS:

The overall percentage agreement was 95.6% (two-sided 95% CI 91.8–98), with a positive percentage agreement (i.e., sensitivity) of 100% (95% CI 94.7–100) and a negative percentage agreement (i.e., specificity) of 95.6% (95% CI 90.6–98.4). All QFT-Plus positive specimens with TB1-Nil and TB2-Nil values less than 1 IU/ml tested positive on QIAreach-QFT.

CONCLUSIONS:

QIAreach QFT is a deployable, accurate testing solution for decentralised testing. It has the potential to overcome key hurdles for TB infection screening in high-burden settings thus helping to achieve the WHO End TB programme goals.