Point-of-care diagnosis of tuberculosis: Past, present and future

Microfluidic platform for the enzymatic pretreatment of human serum for the detection of the tuberculosis biomarker mannose-capped lipoarabinomannan

Tuberculosis (TB) represents a major public health threat, with millions of new cases reported worldwide each year. A major hurdle to curtailing the spread of this disease is the need for low-cost, point-of-care (PoC) diagnostics. Mannose-capped lipoarabinomannan, a significant component of the Mycobacterium tuberculosis bacillus, has been heavily studied as a biomarker for TB, but with little success due to its complexation with endogenous components of body fluids in a manner that sterically interferes with its detection by ELISA and other immunoassays. Recent work by our group and others has shown that complexation can be disrupted with protein-denaturing protocols. By way of followup, we recently described an enzymatic digestion (Proteinase K) sample pretreatment that enables quantitative recovery of ManLAM spiked into healthy human control serum. Herein, we report on the transfer of our benchtop sample pretreatment methodology to an automated microfluidic platform. We show that this platform can be configured to: (1) carry out the pretreatment process with very little user interaction and, (2) yield recoveries for ManLAm spiked into control serum which are statistically indistinguishable from those achieved by the benchtop process. Plans to integrate this device with a portable sample reader as a possible basis for a PoC TB diagnostic system and analyze patient samples are briefly discussed.

Microfluidic systems for infectious disease diagnostics

Microorganisms, encompassing both uni- and multicellular entities, exhibit remarkable diversity as omnipresent life forms in nature. They play a pivotal role by supplying essential components for sustaining biological processes across diverse ecosystems, including higher host organisms. The complex interactions within the human gut microbiota are crucial for metabolic functions, immune responses, and biochemical signalling, particularly through the gut-brain axis. Viruses also play important roles in biological processes, for example by increasing genetic diversity through horizontal gene transfer when replicating inside living cells. On the other hand, infection of the human body by microbiological agents may lead to severe physiological disorders and diseases. Infectious diseases pose a significant burden on global healthcare systems, characterized by substantial variations in the epidemiological landscape. Fast spreading antibiotic resistance or uncontrolled outbreaks of communicable diseases are major challenges at present. Furthermore, delivering field-proven point-of-care diagnostic tools to the most severely affected populations in low-resource settings is particularly important and challenging. New paradigms and technological approaches enabling rapid and informed disease management need to be implemented. In this respect, infectious disease diagnostics taking advantage of microfluidic systems combined with integrated biosensor-based pathogen detection offers a host of innovative and promising solutions. In this review, we aim to outline recent activities and progress in the development of microfluidic diagnostic tools. Our literature research mainly covers the last 5 years. We will follow a classification scheme based on the human body systems primarily involved at the clinical level or on specific pathogen transmission modes. Important diseases, such as tuberculosis and malaria, will be addressed more extensively.

Patterns of childhood tuberculosis diagnosis in Ethiopia: A multicenter cross-sectional study

Background

Children share 12% of the global 10 million people infected with tuberculosis (TB) each year. Closing case detection gap in children remains difficult, with 56% of all children and 65% under-five with TB missed each year. We aimed to assess the patterns of childhood TB diagnosis and underlying determinants in Ethiopia when different TB diagnostic platforms are applied.

Methods

A multi-site, cross-sectional study was carried out in Ethiopia as part of the larger EXIT-TB study - evidence-based multiple focused integrated intensified TB screening package. Outpatient children aged ≤ 15 with cough of any duration seeking care at four healthcare facilities in Ethiopia were enrolled consecutively. Participants underwent sputum Xpert MTB/RIF and/or smear microscopy and posteroanterior chest X-ray (CXR), and their clinical and sociodemographic data were captured using a structured questionnaire. Data were analyzed using Stata version 23. Multiple regression model was computed to determine the factors that influence TB case detection, with a 95% confidence interval (CI) and p < 0.05 taken as statistically significant.

Results

A total of 438 children were enrolled. Of these, 399 had CXR examination of which 55 (13.8%) were suggestive of TB, 270 had Xpert MTB/RIF testing of which 32 (11.9%) were positive, and AFB smear microscopy was done for 51 children of which 2 (3.9%) were positive. Febrile children were more likely to be diagnosed with pulmonary TB than those without fever [aPR = 1.3, 95% CI (1.1-1.4)], and those with a TB contact history were more likely to be diagnosed with pulmonary TB than those with no such contacts [aPR = 1.2, 95% CI (1.1-1.3)]. Children from rural residences were more likely to be diagnosed with TB than those from urban residences [aPR = 1.3, 95% CI (1.1-1.5)].

Conclusion

The findings showed that clinical diagnosis remains an important method of TB diagnosis in children and the preferred choice to avert underdiagnosis. A more sensitive TB diagnostic method for children was symptom screening, followed by CXR and Xpert MTB/RIF assay or smear microscopy. Hence, an algorithm that combines clinical, CXR, and microbiological confirmatory tests can improve the rate of pulmonary TB diagnosis in children till more accurate and cost-effective diagnostic tools are accessible. Fever, weight loss, and TB contact history are highly associated with TB positivity rates in children.

Detection of tuberculosis-associated compounds from human skin by GCxGC-TOFMS

Tuberculosis (TB) remains a global health concern. This study aimed to investigate the potential of human skin volatile organic compounds (VOCs) as prospective biomarkers for TB diagnosis. It employed a non-invasive approach using a wearable silicone rubber band for VOC sampling, comprehensive gas chromatography - time of flight mass spectrometry (GCxGC-TOFMS), and chemometric techniques. Both targeted and untargeted biochemical screening was utilized to explore biochemical differences between healthy individuals and those with TB infection. Results confirmed a correlation between compounds found in this study, and those reported for TB from other biofluids. In a comparison to known TB-associated compounds from other biofluids our analysis established the presence of 27 of these compounds emanating from human skin. Additionally, 16 previously unreported compounds were found as potential biomarkers. The diagnostic ability of the VOCs selected by statistical methods was investigated using predictive modelling techniques. Artificial neural network multi-layered perceptron (ANN) yielded two compounds, 1H-indene, 2,3 dihydro-1,1,3-trimethyl-3-phenyl; and heptane-3-ethyl-2-methyl, as the most discriminatory, and could differentiate between TB-positive (n = 15) and TB-negative (n = 23) individuals with an area under the receiver operating characteristic curve (AUROC) of 92 %, a sensitivity of 100 % and a specificity of 94 % for six targeted features. For untargeted analysis, ANN assigned 3-methylhexane as the most discriminatory between TB-positive and TB- negative individuals. An AUROC of 98.5 %, a sensitivity of 83 %, and a specificity of 88 % were obtained for 16 untargeted features as chosen by high performance variable selection. The obtained values compare highly favourable to alternative diagnostic methods such as breath analysis and GeneXpert. Consequently, human skin VOCs hold considerable potential as a TB diagnostic screening test.

Direct detection of Mycobacterium bovis by a dry loop-mediated isothermal amplification assay in cattle samples collected during routine abattoir examination in Malawi

The lack of quick, accurate, and low-cost detection methods has hindered the active control strategies for bovine tuberculosis (bTB) in resource-limited countries with a high burden of disease. We developed a dry loop-mediated isothermal amplification (LAMP) assay for rapid and specific detection of Mycobacterium bovis, the principal causative agent of bTB, and evaluated the efficacy of the assay using suspected bTB samples collected during routine meat inspection at major regional abattoirs in Malawi. Template genomic DNA was extracted directly from the granulomatous bTB-like lesion (crude extracted DNA), as well as growth from the incubated mycobacterial growth indicator tubes (MGIT). Field results were visualized by the naked eye within 40 min following a color change of the amplified products. The sensitivity and specificity of the dry LAMP assay while using 152 DNA samples extracted from MGIT with confirmed M. bovis results were 98% and 88%, respectively. When 43 randomly selected crude DNA samples from lesions were used, the sensitivity and specificity of the dry LAMP assay were 100% and 75%, respectively. Our LAMP assay offers the potential to meet the demands for a low-cost and rapid field detection tool for bTB in resource-limited countries in which bTB is endemic.

Point-of-care test for tuberculosis: a boon in diagnosis

Rapid diagnosis of tuberculosis (TB) is an effective measure to eradicate this infectious disease worldwide. Traditional methods for screening TB patients do not provide an immediate diagnosis and thus delay treatment. There is an urgent need for the early detection of TB through point-of-care tests (POCTs). Several POCTs are widely available at primary healthcare facilities that assist in TB screening. In addition to the currently used POCTs, advancements in technology have led to the discovery of newer methods that provide accurate and fast information independent of access to laboratory facilities. In the present article, the authors tried to include and describe the potential POCTs for screening TB in patients. Several molecular diagnostic tests, such as nucleic acid amplification tests, including GeneXpert and TB-loop-mediated isothermal amplification, are currently being used as POCTs. Besides these methods, the pathogenic component of Mycobacterium tuberculosis can also be utilized as a biomarker for screening purposes through immunological assays. Similarly, the host immune response to infection has also been utilized as a marker for the diagnosis of TB. These novel biomarkers might include Mtb85, interferon-γ inducible protein-10, volatile organic compounds, acute-phase proteins, etc. Radiological tests have also been observed as POCTs in the TB screening POCT panel. Various POCTs are performed on samples other than sputum, which further eases the screening process. These POCTs should not require large-scale manpower and infrastructure. Hence, POCT should be able to identify patients with M. tuberculosis infection at the primary healthcare level only. There are several other advanced techniques that have been proposed as future POCTs and have been discussed in the present article.

Azide-Masked Fluorescence Turn-On Probe for Imaging Mycobacteria

A fluorescence turn-on probe, an azide-masked and trehalose-derivatized carbazole (Tre-Cz), was developed to image mycobacteria. The fluorescence turn-on is achieved by photoactivation of the azide, which generates a fluorescent product through an efficient intramolecular C-H insertion reaction. The probe is highly specific for mycobacteria and could image mycobacteria in the presence of other Gram-positive and Gram-negative bacteria. Both the photoactivation and detection can be accomplished using a handheld UV lamp, giving a limit of detection of 103 CFU/mL, which can be visualized by the naked eye. The probe was also able to image mycobacteria spiked in sputum samples, although the detection sensitivity was lower. Studies using heat-killed, stationary-phase, and isoniazid-treated mycobacteria showed that metabolically active bacteria are required for the uptake of Tre-Cz. The uptake decreased in the presence of trehalose in a concentration-dependent manner, indicating that Tre-Cz hijacked the trehalose uptake pathway. Mechanistic studies demonstrated that the trehalose transporter LpqY-SugABC was the primary pathway for the uptake of Tre-Cz. The uptake decreased in the LpqY-SugABC deletion mutants ΔlpqY, ΔsugA, ΔsugB, and ΔsugC and fully recovered in the complemented strain of ΔsugC. For the mycolyl transferase antigen 85 complex (Ag85), however, only a slight reduction of uptake was observed in the Ag85 deletion mutant ΔAg85C, and no incorporation of Tre-Cz into the outer membrane was observed. The unique intracellular incorporation mechanism of Tre-Cz through the LpqY-SugABC transporter, which differs from other trehalose-based fluorescence probes, unlocks potential opportunities to bring molecular cargoes to mycobacteria for both fundamental studies and theranostic applications.

Biofabrication of Multiplexed Electrochemical Immunosensors for Simultaneous Detection of Clinical Biomarkers in Complex Fluids

Simultaneous detection of multiple disease biomarkers in unprocessed whole blood is considered the gold standard for accurate clinical diagnosis. Here, this study reports the development of a 4-plex electrochemical (EC) immunosensor with on-chip negative control capable of detecting a range of biomarkers in small volumes (15 µL) of complex biological fluids, including serum, plasma, and whole blood. A framework for fabricating and optimizing multiplexed sandwich immunoassays is presented that is enabled by use of EC sensor chips coated with an ultra-selective, antifouling, and nanocomposite coating. Cyclic voltammetry evaluation of sensor performance is carried out by monitoring the local precipitation of an electroactive product generated by horseradish peroxidase linked to a secondary antibody. EC immunosensors demonstrate high sensitivity and specificity without background signal with a limit of detection in single-digit picogram per milliliter in multiple complex biological fluids. These multiplexed immunosensors enable the simultaneous detection of four different biomarkers in plasma and whole blood with excellent sensitivity and selectivity. This rapid and cost-effective biosensor platform can be further adapted for use with different high affinity probes for any biomarker, and thereby create for a new class of highly sensitive and specific multiplexed diagnostics.

TB testing in HIV-positive patients prior to antiretroviral treatment

BACKGROUND: TB diagnosis in patients with HIV is challenging due to the lower sensitivities across tests. Molecular tests are preferred and the Xpert^® MTB/RIF assay has limitations in lower-income settings. We evaluated the performance of loop-mediated isothermal amplification (LAMP) and the lipoarabinomannan (LAM) test in HIV-positive, ART-naïve clinic patients.METHODS: A total of 783 eligible patients were enrolled; three spot sputum samples of 646 patients were tested using TB-LAMP, Xpert, smear microscopy and culture, while 649 patients had TB-LAM testing. Sensitivity, specificity, and negative and positive predictive values were estimated with 95% confidence intervals.RESULTS: Sensitivities for smear microscopy, TB-LAMP and Xpert were respectively 50%, 63% and 74% compared to culture, with specificities of respectively 99.2%, 98.5% and 97.5%. An additional eight were positive on TB-LAM alone. Seventy TB patients (9%) were detected using standard-of-care testing, an additional 27 (3%) were detected using study testing. Treatment was initiated in 57/70 (81%) clinic patients, but only in 56% (57/97) of all those with positive TB tests; 4/8 multidrug-resistant samples were detected using Xpert.CONCLUSION: TB diagnostics continue to miss cases in this high-burden setting. TB-LAMP was more sensitive than smear microscopy, and if followed by culture and drug susceptibility testing as required, can diagnose TB in HIV-positive patients. TB-LAM is a useful add-in test and both tests at the point-of-care would maximise yield.

Tuberculosis Prevalence and Predictors Among Health Care-Seeking People Screened for Cough of Any Duration in Ethiopia: A Multicenter Cross-Sectional Study

Background

Tuberculosis (TB) remains a major cause of morbidity and mortality in sub-Saharan Africa. This high burden is mainly attributed to low case detection and delayed diagnosis. We aimed to determine the prevalence and predictors of TB among health care-seeking people screened for cough of any duration in Ethiopia.

Methods

In this multicenter cross-sectional study, we screened 195,713 (81.2%) for cough of any duration. We recruited a sample of 1,853 presumptive TB (PTB) cases and assigned them into three groups: group I with cough ≥2 weeks, group II with cough of <2 weeks, and group III pregnant women, patients on antiretroviral therapy, and patients with diabetes. The first two groups underwent chest radiograph (CXR) followed by sputum Xpert MTB/RIF assay or smear microscopy. The third group was exempted from CXR but underwent sputum Xpert MTB/RIF assay or smear microscopy. TB prevalence was calculated across the groups and TB predictors were analyzed using modified Poisson regression to compute adjusted prevalence ratio (aPR) with a 95% confidence interval (CI).

Results

The overall prevalence of PTB was 16.7% (309/1853). Of the positive cases, 81.2% (251/309) were in group I (cough ≥2 weeks), 14.2% (44/309) in group II (cough of <2), and 4.5% (14/309) in group III (CXR exempted). PTB predictors were age group of 25-34 [aPR = 2.0 (95% CI 1.3-2.8)], history of weight loss [aPR = 1.2 (95% CI 1.1-1.3)], and TB suggestive CXRs [aPR = 41.1 (95% CI 23.2-72.8)].

Conclusion

The prevalence of confirmed PTB among routine outpatients was high, and this included those with a low duration of cough who can serve as a source of infection. Screening all patients at outpatient departments who passively report any cough irrespective of duration is important to increase TB case finding and reduce TB transmission and mortality.

Diagnostic value of Lipoarabinomannan antigen for detecting Mycobacterium tuberculosis in adults and children with or without HIV infection

Objectives

Even today, tuberculosis (TB) remains a leading public health problem; yet, the current diagnostic methods still have a few shortcomings. Lipoarabinomannan (LAM) provides an opportunity for TB diagnosis, and urine LAM detection seems to have a promising and widely applicable prospect.

Design or methods

Four databases were systematically searched for eligible studies, and the quality of the studies was evaluated using the quality assessment of diagnostic accuracy studies‐2 (QUADAS‐2). Graphs and tables were created to show sensitivity, specificity, likelihood ratios, diagnostic odds ratio (DOR), the area under the curve (AUC), and so on.

Results

Based on the included 67 studies, the pooled sensitivity of urine LAM was 48% and specificity was 89%. In the subgroup analyses, the FujiLAM test had higher sensitivity (69%) and specificity (92%). Furthermore, among patients infected with human immunodeficiency virus (HIV), 50% of TB patients were diagnosed using a urine LAM test. Besides, the CD4+ cell count was inversely proportional to the sensitivity.

Conclusions

Urine LAM is a promising diagnostic test for TB, particularly using the FujiLAM in HIV‐infected adults whose CD4+ cell count is ≤100 per μl. Besides, the urine LAM test shows various sensitivities and specificities in different subgroups in terms of age, HIV infection status, CD4+ cell count, and testing method.

User perspectives and preferences on a novel TB LAM diagnostic (Fujifilm SILVAMP TB LAM)-a qualitative study in Malawi and Zambia

Widely available tuberculosis (TB) diagnostics use sputum samples. However, many patients, particularly children and patients living with HIV (PLHIV), struggle to provide sputum. Urine diagnostics are a promising approach to circumvent this challenge while delivering reliable and timely diagnosis. This qualitative study in two high TB/HIV burden countries assesses values and preferences of end-users, along with potential barriers for the implementation of the novel Fujifilm SILVAMP TB-LAM (FujiLAM, Fujifilm, Japan) urine test. Between September 2020 and March 2021, we conducted 42 semi-structured interviews with patients, health care providers (HCPs) and decision makers (DMs) (e.g., in national TB programs) in Malawi and Zambia. Interviews were transcribed verbatim and analyzed using a framework approach supported by NVIVO. Findings aligned with the pre-existing Health Equity Implementation Framework, which guided the presentation of results. The ease and convenience of urine-based testing was described as empowering among patients and HCPs who lamented the difficulty of sputum collection, however HCPs expressed concerns that a shift in agency to the patient may affect clinic workflows (e.g., due to less control over collection). Implementation facilitators, such as shorter turnaround times, were welcomed by operators and patients alike. The decentralization of diagnostics was considered possible with FujiLAM by HCPs and DMs due to low infrastructure requirements. Finally, our findings support efforts for eliminating the CD4 count as an eligibility criterion for LAM testing, to facilitate implementation and benefit a wider range of patients. Our study identified barriers and facilitators relevant to scale-up of urine LAM tests in Malawi and Zambia. FujiLAM could positively impact health equity, as it would particularly benefit patient groups currently underserved by existing TB diagnostics. Participants view the approach as a viable, acceptable, and likely sustainable option in low- and middle-income countries, though adaptations may be required to current health care processes for deployment. Trial registration: German Clinical Trials Register, DRKS00021003. URL: https://www.drks.de/drks_web/setLocale_EN.do.

Evidence of TB Services at Primary Healthcare Level during COVID-19: A Scoping Review

Tuberculosis (TB) is still a major public health concern, despite the availability of preventative and curative therapies. Significant progress has been made in the past decade towards its control. However, the emergence of the novel coronavirus disease 2019 (COVID-19) has disrupted numerous essential health services, including those for TB. This scoping review maps the available evidence on TB services at the primary healthcare (PHC) level during the COVID-19 period. A comprehensive literature search was conducted in PubMed, Web of Science, Medline OVID, Medline EBSCO, and Scopus. A total of 820 articles were retrieved from the databases and 21 met the eligibility criteria and were used for data extraction. The emerging themes were the effect of the COVID-19 pandemic on TB services, patient and provider experiences, recommendations for TB services during the COVID-19 period, and the implementation of the recommendations. The review found that the mitigation strategies, as well as fear and stigma experienced at the start of the COVID-19 pandemic may have led to TB cases potentially going undetected, which may threaten TB treatment outcomes. Therefore, efforts must be directed at finding these missing cases and ensuring that PHC facilities are equipped to adequately diagnose and treat them.

Clinical features of atypical tuberculosis mimicking bacterial pneumonia

OBJECTIVES

The aim of this study is to investigate clinical features of atypical pulmonary tuberculosis (aPTB) mimicking bacterial pneumonia, determine imaging features with the highest degree of correlation, and identify predictors for acid-fast bacilli (AFB) positivity.

METHODS

The clinical data of 259 patients considered as aPTB were retrospectively analyzed. The correlation of CT patterns was evaluated with Spearman analysis, and the predictors for AFB positivity were assessed with the multivariate analysis.

RESULTS

The most common symptom of aPTB was cough (84.6%), followed by fever and anorexia (47.1 and 41.7%, respectively). Infiltrated patchy was the most common radiological pattern (84.9%), followed by nodules (3-10 mm), micronodules (<3 mm), and consolidation (79.2, 78.8, and 66.0%, respectively). Nodules (3-10 mm) and micronodules (r = 0.988, p < 0.001), consolidation and air bronchogram (r = 0.590, p < 0.001), and pulmonary atelectasis and consolidation (r = 0.323, p < 0.001) showed high correlation. In the multivariate analysis, hyperpyrexia (OR, 2.29; 95% CI, 1.22-4.29) and bronchiectasis (OR, 2.06; 95% CI, 1.04-4.06) were the predictors of AFB-smear positivity, while bulla (OR, 0.22; 95% CI, 0.05-0.97) was the predictor of AFB-smear negativity.

CONCLUSION

This study demonstrated the clinical and radiological features of aPTB mimicking pneumonia. Several paired radiological findings may guide us to the diagnosis of aPTB. Hyperpyrexia and bronchiectasis may be helpful for predicting AFB positivity, and bulla may be a predictive sign of AFB negativity.

Xpert MTB/RIF Ultra is highly sensitive for the diagnosis of tuberculosis lymphadenitis in an HIV-endemic setting

Tuberculosis lymphadenitis (TBL) is the most common extrapulmonary tuberculosis (EPTB) manifestation. Xpert MTB/RIF Ultra (Ultra) is a World Health Organization-endorsed diagnostic test, but performance data for TBL, including on noninvasive specimens, are limited. Fine-needle aspiration biopsy specimens (FNABs) from outpatients (≥18 years) with presumptive TBL (n = 135) underwent (i) routine Xpert MTB/RIF testing (later with Ultra once programmatically available), (ii) MGIT 960 culture (if Xpert or Ultra negative or rifampicin resistant), and (iii) study Ultra testing. Concentrated paired urine specimens underwent Ultra testing. Primary analyses used a microbiological reference standard (MRS). In a head-to-head comparison (n = 92) of an FNAB study Ultra and Xpert, Ultra had increased sensitivity (91% [95% confidence interval: 79, 98] versus 72% [57, 84]; P = 0.016) and decreased specificity (76% [61, 87] versus 93% [82, 99]; P = 0.020) and diagnosed patients not on treatment. Neither HIV nor alternative reference standards affected sensitivity and specificity. In patients with both routine and study Ultra tests, the latter detected more cases (+20% [0, 42]; P = 0.034), and false-negative study Ultra results were more inhibited than true-positive results. Study Ultra false positives had less mycobacterial DNA than true positives (trace-positive proportions, 59% [13/22] versus 12% [5/51]; P < 0.001). “Trace” exclusion or recategorization removed potential benefits offered over Xpert. Urine Ultra tests had low sensitivity (18% [7, 35]). Ultra testing on FNABs is highly sensitive and detects more TBL than Xpert (Ultra still missed some cases due in part to inhibition). Patients with FNAB Ultra-positive “trace” results, most of whom will be culture negative, may require additional clinical investigation. Urine Ultra testing could reduce the number of patients needing invasive sampling.

Engineered Mycobacterium tuberculosis antigen assembly into core-shell nanobeads for diagnosis of tuberculosis

Despite recent advances in diagnosis, tuberculosis (TB) remains one of the ten leading causes of death worldwide. Here, we engineered Mycobacterium tuberculosis (Mtb) proteins (ESAT6, CFP10, and MTB7.7) to self-assemble into core-shell nanobeads for enhanced TB diagnosis. Respective purified Mtb antigen-coated polyester beads were characterized and their functionality in TB diagnosis was tested in whole blood cytokine release assays. Sensitivity and specificity were studied in 11 pulmonary TB patients (PTB) and 26 healthy individuals composed of 14 Tuberculin Skin Test negative (TSTn) and 12 TST positive (TSTp). The production of 6 cytokines was determined (IFNγ, IP10, IL2, TNFα, CCL3, and CCL11). To differentiate PTB from healthy individuals (TSTp + TSTn), the best individual cytokines were IL2 and CCL11 (>80% sensitivity and specificity) and the best combination was IP10 + IL2 (>90% sensitivity and specificity). We describe an innovative approach using full-length antigens attached to biopolyester nanobeads enabling sensitive and specific detection of human TB.

Gene Xpert/MTB RIF assay for spinal tuberculosis- sensitivity, specificity and clinical utility

BACKGROUND

Xpert MTB/RIF assay is a rapid automated molecular test with excellent reported sensitivity, specificity for diagnosis of pulmonary and extrapulmonary Mycobacterium tuberculosis (MTB) infections. However, the clinical utility and accuracy in STB is not well established. A study was conducted to report on the sensitivity, specificity and clinical utility of the Xpert MTB/RIF assay in spinal tuberculosis (STB).

METHODS

A retrospective review of medical records was performed for 136 patients that underwent spinal biopsy for suspected spondylodiscitis. Reports for acid fast bacilli (AFB) smear, gram stain, pyogenic culture, MTB culture, histopathology, Xpert MTB/RIF assay, and drug sensitivity testing were reviewed. 'Reference standard for diagnosis of STB' was based on positive histopathology and/or MTB culture evidence and was considered as MTB positive. Any samples returning a positive pyogenic or fungal culture were considered as MTB negative. The sensitivity, specificity for Xpert MTB/RIF was assessed against the reference standard.

RESULTS

A total of 125 patients were considered for final analysis, 86 patients met the criteria for 'Reference standard for diagnosis of TB spine' (MTB positive). This includes nine patients that were MGIT culture only positive; 45 that were histopathology only positive and 32 were both culture and histopathology positive. There were 39 culture proven (pyogenic-37 and fungal-2) patients included in MTB negative group. The 86 MTB positive patients, included 53 (61.6%) tissue samples and 33 (38.4%) pus samples. The overall analysis showed a 65.1% sensitivity, 100% specificity, 100% PPV and 56.5% NPV for the Xpert MTB/RIF.

CONCLUSIONS

Gene Xpert MTB/RIF showed excellent specificity and was accurate in the identification of drug resistance. The sensitivity was 65% and sampling techniques using pus samples rather than tissue samples could be a possible reason for lower sensitivity.

Rats sniff out pulmonary tuberculosis from sputum: a diagnostic accuracy meta-analysis

In Sub-Saharan Africa, African giant pouched rats (Cricetomys gambianus) are trained to identify TB patients by smelling sputum. We conducted a systematic review and meta-analysis of the data to see if this novel method is comparable to traditional laboratory screening and detection methods like Ziehl-Neelsen stain-based assays (ZN) and bacterial culture. The search and data processing strategy is registered at PROSPERO (CRD42019123629). Medline via PubMed, EMBASE, Web of Science, and Cochrane Library databases were systematically searched for the keywords "pouched rat" and "tuberculosis". Data from 53,181 samples obtained from 24,600 patients were extracted from seven studies. Using sample-wise detection, the sensitivity of the studies was 86.7% [95% CI 80.4-91.2%], while the specificity was 88.4% [95% CI 79.7-93.7%]. For patient-wise detection, the sensitivity was 81.3% [95% CI 64.0-91.4%], while the specificity was 73.4% [95% CI 62.8-81.9%]. Good and excellent classification was assessed by hierarchical summary receiver-operating characteristic analysis for patient-wise and sample-wise detections, respectively. Our study is the first systematic review and meta-analysis of the above relatively inexpensive and rapid screening method. The results indicate that African giant pouched rats can discriminate healthy controls from TB individuals by sniffing sputum with even a higher accuracy than a single ZN screening.

Mycobacterium bovis and you: A comprehensive look at the bacteria, its similarities to Mycobacterium tuberculosis, and its relationship with human disease

While Mycobacterium tuberculosis is the primary cause of tuberculosis in people, multiple other mycobacteria are capable of doing so. With the World Health Organization's goal of a 90% reduction in tuberculosis by 2035, all tuberculous mycobacteria need to be addressed. Understanding not only the similarities, but importantly the differences between the different species is crucial if eradication is ever to be achieved. Mycobacterium bovis, while typically thought of as a disease of cattle, remains a possible source of human infection worldwide. Although this species' genome differs from Mycobacterium tuberculosis by only 0.05%, significant differences are present, creating unique challenges to address. This review focuses on features which distinguish this bacterium from Mycobacterium tuberculosis, including differences in origin, structure, environmental persistence, host preferences, infection and disease, host immune response, diagnostics and treatment.

Aptamer-Based Detection of Ampicillin in Urine Samples

The misuse of antibiotics in health care has led to increasing levels of drug resistant infections (DRI's) occurring in the general population. Most technologies developed for the detection of DRI's typically focus on phenotyping or genotyping bacterial resistance rather than on the underlying cause and spread of DRI's; namely the misuse of antibiotics. An aptameric based assay has been developed for the monitoring of ampicillin in urine samples, for use in determining optimal antibiotic dosage and monitoring patient compliance with treatment. The fluorescently labelled aptamers were shown to perform optimally at pH 7, ideal for buffered clinical urine samples, with limits of detection as low as 20.6 nM, allowing for determination of ampicillin in urine in the clinically relevant range of concentrations (100 nM to 100 µM). As the assay requires incubation for only 1 h with a small sample volume, 50 to 150 µL, the test would fit within current healthcare pathways, simplifying the adoption of the technology.

An Optimal Diagnostic Strategy for Tuberculosis in Hospitalized HIV-Infected Patients Using GeneXpert MTB/RIF and Alere Determine TB LAM Ag

The diagnosis of tuberculosis (TB) in HIV-infected patients is challenging. Both a urinary lipoarabinomannan (LAM) test (Alere TB LAM) and GeneXpert-MTB/RIF (Xpert) are useful for the diagnosis of TB. However, how to optimally integrate Xpert and LAM tests into clinical practice algorithms remain unclear. We performed a post hoc analysis of 561 HIV-infected sputum-expectorating patients (median CD4 count of 130 cells/ml) from a previously published randomized controlled trial evaluating the LAM test in hospitalized HIV-infected patients with suspected TB. We evaluated 5 different diagnostic strategies using sputum culture as a reference standard (Xpert alone, LAM alone, sequential Xpert followed by LAM and vice versa [LAM in Xpert-negative patients and Xpert in LAM-negative patients], and both tests concurrently [LAM + Xpert]). A cost-consequence analysis was performed. Strategy-specific sensitivity and specificity, using culture as a reference, were similar with the Xpert-only and sequential and concurrent strategies. However, when any positive TB-specific test was used as a reference, the incremental yield of LAM over Xpert was 29.6% (45/152) and that of Xpert over LAM was 75% (84/11). The incremental yield of LAM increased with decreasing CD4 count. The costs per TB case diagnosed were similar for the sequential and concurrent strategies ($1,617 to $1,626). In sputum-expectorating hospitalized patients with advanced HIV and access to both tests, concurrent testing with Xpert and LAM may be the best strategy for diagnosing TB. These data inform clinical practice in settings where TB and HIV are endemic.

Sensitivity and Specificity of Gene Xpert in the Diagnosis of Spinal Tuberculosis: A Prospective Controlled Clinical Study

STUDY DESIGN

Prospective matched cohort study.

OBJECTIVE

To evaluate the sensitivity and specificity of Gene Xpert in the diagnosis of spinal tuberculosis.

METHODS

From January 2016 to August 2018, Gene Xpert results were prospectively studied in 68 patients of clinicoradiologically suspected spinal tuberculosis (STB) and a control group (CG) of 92 patients, all of whom underwent computed tomography-guided/C-arm-guided/open surgical biopsy. Sensitivity, specificity, positive predictive value, and negative predictive value are obtained using standard equations.

RESULTS

Out of 68 cases of STB, Gene Xpert was positive in 62 (true positive: 62/68) and negative in 6 (false negative: 6/68). Gene Xpert was negative for all 92 cases of CG (true negative: 92/92, false positive 0/92). Thus, in our series, sensitivity of Gene Xpert is 91.18%, specificity is 100%, positive predictive value is 100%, and negative predictive value is 93.88%. Out of all cases of STB, 62/68 (91.18%) were Gene Xpert positive, but only 35/64 (54.69%) was acid-fast bacilli (AFB) culture positive and 53/60(88.33%) was histopathologically conclusive of TB. Also, Gene Xpert was positive in 7/7 (100%) cases of STB in which histopathology were inconclusive and 25/29 (86.21%) cases of STB in which AFB culture was negative.

CONCLUSION

In STB, Gene Xpert clearly outperforms AFB culture and histopathology due to its high sensitivity and specificity apart from being rapid in diagnosis. Hence it is justified to diagnose spinal tuberculosis by Gene Xpert though histopathology is confirmative and AFB culture remains the gold standard.

A plasmonic fiberoptic absorbance biosensor for mannose-capped lipoarabinomannan based tuberculosis diagnosis

Tuberculosis (TB) is a resurgent infectious disease affecting a large number of people in the developing countries. An on-site, affordable diagnostic screening at an early-stage for an immediate anti-TB treatment is known to tremendously minimize the high mortality rates. Lipoarabinomannan (LAM), a surface glycolipid, has been identified as a potential TB biomarker present in urine at ultra-low concentrations of a few fg/mL. Here, we report a plasmonic fiber optic absorbance biosensor (P-FAB) strategy for mannosylated LAM (Man-LAM or Mtb LAM) detection down to attomolar concentrations. It involves a plasmonic sandwich immunoassay on a U-bent fiber optic probe with gold plasmonic (AuNP) labels functionalized with anti-Mtb LAM immunoglobulin M (IgM) and anti-Mtb LAM IgG respectively. The Mtb LAM is quantified in terms of absorption of light passing through the fiber probe using a green LED and a photodetector. The choice of fiber optic probes (fused silica versus polymer), the optimum size (20, 40, 60 and 80 nm) and concentration (2 × , 10 × , and 20 × ) of AuNP labels were investigated to obtain high sensitivity and lower limits of analyte detection (LoD). P-FAB with a simple LED-photodetector pair, 200 μm fused silica U-bent fiber probe and 60 nm (20 × ) AuNP labels gave LoDs down to 1 fg/mL and 10 fg/mL in the buffer and synthetic urine respectively. Moreover, the anti-Mtb LAM IgM bound sensor probes and the AuNP reagent stored at 4 °C were stable up to 45 days. P-FAB based Mtb LAM sensor demonstrates its potential for an on-site TB diagnosis.

Carbon nanotube-based thin-film resistive sensor for point-of-care screening of tuberculosis

For point-of-care diagnosis of tuberculosis (TB), current TB diagnostic approaches need to be further improved for achieving an accurate diagnosis that is rapid and low-cost. This paper presents an immuno-resistive sensor on a plastic film for inexpensive, simple TB screening. The sensor is composed of single-walled carbon nanotubes (SWCNTs) functionalized with polyclonal antibodies raised against the MPT64 surface antigen from Mycobacterium tuberculosis (MTB). The target analyte of either MTB or MPT64 is spiked in tongue swab and sputum samples. Under optimized conditions, targets are directly detected from tongue swab samples by resistive measurement. Target analytes spiked into human sputa are enriched with a magnetic bead protocol followed by resistive detection. This highly sensitive film sensor will facilitate rapid TB screening with the added benefits of a small form factor, simple operation, low power requirement, and low cost.

Ultrasound in managing extrapulmonary tuberculosis: a randomized controlled two-center study

BACKGROUND

Patients with clinically suspected tuberculosis are often treated empirically, as diagnosis - especially of extrapulmonary tuberculosis - remains challenging. This leads to an overtreatment of tuberculosis and to underdiagnosis of possible differential diagnoses.

METHODS

This open-label, parallel-group, superiority randomized controlled trial is done in a rural and an urban center in Tanzania. HIV-positive and -negative adults (≥18 years) with clinically suspected extrapulmonary tuberculosis are randomized in a 1:1 ratio to an intervention- or control group, stratified by center and HIV status. The intervention consists of a management algorithm including extended focused assessment of sonography for HIV and tuberculosis (eFASH) in combination with chest X-ray and microbiological tests. Treatment with anti-tuberculosis drugs is started, if eFASH is positive, chest X-ray suggests tuberculosis, or a microbiological result is positive for tuberculosis. Patients in the control group are managed according national guidelines. Treatment is started if microbiology is positive or empirically according to the treating physician. The primary outcome is the proportion of correctly managed patients at 6 months (i.e patients who were treated with anti-tuberculosis treatment and had definite or probable tuberculosis, and patients who were not treated with anti-tuberculosis treatment and did not have tuberculosis). Secondary outcomes are the proportion of symptom-free patients at two and 6 months, and time to death. The sample size is 650 patients.

DISCUSSION

This study will determine, whether ultrasound in combination with other tests can increase the proportion of correctly managed patients with clinically suspected extrapulmonary tuberculosis, thus reducing overtreatment with anti-tuberculosis drugs.

TRIAL REGISTRATION

PACTR, Registration number: PACTR201712002829221, registered December 1st 2017.

Accuracy of Two Point-of-Care Tests for Rapid Diagnosis of Bovine Tuberculosis at Animal Level using Non-Invasive Specimens

Bovine tuberculosis (BTB) testing in cattle requires a significant investment of time, equipment, and labor. Novel, rapid, cheaper and accurate methods are needed. The Alere Determine TB lipoarabinomannan antigen (LAM-test) is a World Health Organization-endorsed point-of-care urine test designed to detect active TB disease in humans. The Lionex Animal TB Rapid Test (Lionex-test) is a novel animal specific TB diagnostic blood test. An animal level analysis was performed using urine (n = 141) and milk (n = 63) samples from depopulated BTB-suspected cattle to test the accuracy of the LAM-test when compared to results of positive TB detection by any routine BTB tests (BOVIGAM, necropsy, histology, culture, PCR) that are regularly performed by the United States Department of Agriculture (USDA). The agreement between the urine LAM-test and USDA standard tests were poor at varying testing time points. The same milk samples did not elicit statistically significant agreement with the Lionex-test, although positive trends were present. Hence, we cannot recommend the LAM-test as a valid BTB diagnostic test in cattle using either urine or milk. The Lionex-test’s production of positive trends using milk samples suggests larger sample sizes may validate the Lionex-test in accurately diagnosing BTB in cattle using milk samples, potentially providing a quick and reliable field test for BTB.

Current and emerging trends in point-of-care urinalysis tests

Introduction: The development of point-of-care testing (POCT) has made clinical diagnostics available, affordable, rapid, and easy to use since the 1990s.The significance of this platform rests on its potential to empower patients to monitor their own health status more frequently, in the convenience of their home, so that diseases can be diagnosed at the earliest possible time-point. Recent advances have expanded traditional formats such as qualitative or semi-quantitative dipsticks and lateral flow immunoassays to newer platforms such as microfluidics and paper-based assays where signals can be measured quantitatively using handheld devices.Areas covered: This review discusses: (1) working principles and operating mechanisms of both existing and emerging POCT platforms, (2) urine analytes measured using POCT in comparison to the laboratory or clinical 'gold standard,' and (3) limitations of existing POCT and expectations of emerging POCT in urinalysis.Expert opinion: Currently, a variety of biological samples such as urine, saliva, serum, plasma, and other fluids can be applied to POCT for quick diagnosis, especially in resource-limited settings. Emerging platforms will increasingly empower individuals to monitor their health status through frequent urine analysis even from their homes. The impact of these emerging technologies on healthcare is likely to be transformative.

Improved Alere Determine Lipoarabinomannan Antigen Detection Test for the Diagnosis of Human and Bovine Tuberculosis by Manipulating Urine and Milk

Tuberculosis (TB) disease still kills 1-person every 21-seconds. Few TB diagnostic tests are considered truly appropriate for point of care settings. The WHO-endorsed immunodiagnostic Alere Determine Lipoarabinomannan Ag-test (LAM-test) detects Mycobacterium tuberculosis complex LAM in urine, and its use is recommended for TB diagnosis among HIV co-infected individuals with low CD4 T-cell counts. Here we found that a simple 15-minute enzymatic treatment at room temperature of LAM-spiked urine with α-mannosidase (for human TB), and LAM-spiked milk with combined lactase and caseinase (for bovine TB), enhanced 10-fold the detection levels of the LAM-test and thus, improved the detection of LAM by the LAM-test in urine and milk that otherwise could be missed in the field. Future separate clinical research studies specifically designed to address the potential of these findings are required.

Advances in diagnostic microfluidics

Microfluidics is an emerging field in diagnostics that allows for extremely precise fluid control and manipulation, enabling rapid and high-throughput sample processing in integrated micro-scale medical systems. These platforms are well-suited for both standard clinical settings and point-of-care applications. The unique features of microfluidics-based platforms make them attractive for early disease diagnosis and real-time monitoring of the disease and therapeutic efficacy. In this chapter, we will first provide a background on microfluidic fundamentals, microfluidic fabrication technologies, microfluidic reactors, and microfluidic total-analysis-systems. Next, we will move into a discussion on the clinical applications of existing and emerging microfluidic platforms for blood analysis, and for diagnosis and monitoring of cancer and infectious disease. Together, this chapter should elucidate the potential that microfluidic systems have in the development of effective diagnostic technologies through a review of existing technologies and promising directions.

Rapid and specific labeling of single live Mycobacterium tuberculosis with a dual-targeting fluorogenic probe

Tuberculosis (TB) remains a public health crisis and a leading cause of infection-related death globally. Although in high demand, imaging technologies that enable rapid, specific, and nongenetic labeling of live Mycobacterium tuberculosis (Mtb) remain underdeveloped. We report a dual-targeting strategy to develop a small molecular probe (CDG-DNB3) that can fluorescently label single bacilli within 1 hour. CDG-DNB3 fluoresces upon activation of the β-lactamase BlaC, a hydrolase naturally expressed in Mtb, and the fluorescent product is retained through covalent modification of the Mtb essential enzyme decaprenylphosphoryl-β-d-ribose 2'-epimerase (DprE1). This dual-targeting probe not only discriminates live from dead Bacillus Calmette-Guérin (BCG) but also shows specificity for Mtb over other bacterial species including 43 nontuberculosis mycobacteria (NTM). In addition, CDG-DNB3 can image BCG phagocytosis in real time, as well as Mtb in patients' sputum. Together with a low-cost, self-driven microfluidic chip, we have achieved rapid labeling and automated quantification of live BCG. This labeling approach should find many potential applications for research toward TB pathogenesis, treatment efficacy assessment, and diagnosis.

Ultrasensitive and Portable Assay for Lead(II) Ions by Electronic Balance as a Readout

Lead ions (Pb²⁺) cause harm to human health. Therefore, the development of fast, effective, and convenient sensors for Pb²⁺ monitoring has received great attention. In this study, a portable method has been proposed for Pb²⁺ detection using normal electronic balance as a readout. Magnetic bead-catalytic strand is hybridized with platinum nanoparticles (Pt NPs) functioned substrate strand (Pt-Sub) to form double-stranded DNA first. In the presence of Pb²⁺, the DNAzyme is activated and cleaved at the ribo-adenosine site of the substrate strand and hence causes Pt NPs to be released into the supernatant, which can be easily separated from the Pt-Sub by a magnet. The separated Pt NPs can effectively catalyze the decomposition of H₂O₂ to produce O₂. In a sealed bottle, the pressure inside the bottle is increased by the generation of oxygen so that the water is discharged from the drainage device, and the weight of the water can be easily and precisely measured by a normal electronic balance. The weighting water has a linear relationship with the concentration of Pb²⁺ in the range of 2.5-100 nM and the detection limit of 0.83 nM (S/N = 3). The proposed method has been applied to detect Pb²⁺ in water with satisfactory results. Because the electronic balance is one of the most commonly used analytical tools for the laboratory, it is very practical and convenient without the need for expensive instruments and complicated data processing.

Plasmonic-based platforms for diagnosis of infectious diseases at the point-of-care

Infectious diseases such as HIV-1/AIDS, tuberculosis (TB), hepatitis B (HBV), and malaria still exert a tremendous health burden on the developing world, requiring rapid, simple and inexpensive diagnostics for on-site diagnosis and treatment monitoring. However, traditional diagnostic methods such as nucleic acid tests (NATs) and enzyme linked immunosorbent assays (ELISA) cannot be readily implemented in point-of-care (POC) settings. Recently, plasmonic-based biosensors have emerged, offering an attractive solution to manage infectious diseases in the developing world since they can achieve rapid, real-time and label-free detection of various pathogenic biomarkers. Via the principle of plasmonic-based optical detection, a variety of biosensing technologies such as surface plasmon resonance (SPR), localized surface plasmon resonance (LSPR), colorimetric plasmonic assays, and surface enhanced Raman spectroscopy (SERS) have emerged for early diagnosis of HIV-1, TB, HBV and malaria. Similarly, plasmonic-based colorimetric assays have also been developed with the capability of multiplexing and cellphone integration, which is well suited for POC testing in the developing world. Herein, we present a comprehensive review on recent advances in surface chemistry, substrate fabrication, and microfluidic integration for the development of plasmonic-based biosensors, aiming at rapid management of infectious diseases at the POC, and thus improving global health.

Point of care testing for infectious diseases

Infectious diseases are caused by pathogenic microorganisms and can be transmitted between individuals and populations thus threatening the general public health and potentially the economy. Efficient diagnostic tools are needed to provide accurate and timely guidance for case identification, transmission disruption and appropriate treatment administration. Point of care (POC) tests provide actionable results near the patient and thereby serve as a personal "radar". In this review, we review clinical needs for POC testing for several major pathogens, including malaria parasites, human immunodeficiency virus (HIV), human papillomavirus (HPV), dengue, Ebola and Zika viruses and Mycobacterium tuberculosis (TB). We compare different molecular approaches, including pathogen nucleic acid and protein, circulating microRNA and antibodies, used in the POC tests. Finally, we review recent advances in novel POC technologies focusing on microfluidic and plasmonic-based approaches.

A Feasibility Study for Diagnosis of Latent Tuberculosis Infection Using an IGRA Point-of-Care Platform in South Korea

PURPOSE

This study aimed to evaluate ichroma™ IGRA-TB, a novel point-of-care platform for assaying IFN-γ release, and to compare it with QuantiFERON-TB Gold In-Tube (QFT-GIT) for identifying Mycobacterium tuberculosis (M. tb) infection.

MATERIALS AND METHODS

We recruited 60 healthy subjects, and blood samples were obtained in QFT-GIT blood collection tubes. The blood collection tubes were incubated at 37°C, and culture supernatant was harvested after 18-24 hours. IFN-γ responses were assessed by the ichroma™ IGRA-TB cartridge and the QFT-GIT IFN-γ enzyme-linked immunosorbent assay. Three active TB patients were recruited as a positive control for M. tb infection.

RESULTS

The area under the receiver operating characteristic curve of the ichroma™ IGRA-TB test for differentiating between infected and non-infected individuals was 0.9706 (p<0.001). Inconsistent positivity between the two tests was found in three participants who showed weak positive IFN-γ responses (<1.0 IU/mL) with QFT-GIT. However, the two tests had excellent agreement (95.2%, κ=0.91, p<0.001), and a very strong positive correlation was observed between the IFN-γ values of both tests (r=0.91, p<0.001).

CONCLUSION

The diagnostic accuracy demonstrated in this study indicates that the ichroma™ IGRA-TB test could be used as a rapid diagnostic method for detecting latent TB infection. It may be particularly beneficial in resource-limited places that require cost-effective laboratory diagnostics.

Lipids as Biomarkers of Cancer and Bacterial Infections

Lipids are ubiquitous molecules, known to play important roles in various cellular processes. Alterations to the lipidome can therefore be used as a read-out of the signs of disease, highlighting the importance to consider lipids as biomarkers in addition of nucleic acid and proteins. Lipids are among the primary structural and functional constituents of biological tissues, especially cell membranes. Along with membrane formation, lipids play also a crucial role in cell signalling, inflammation and energy storage. It was shown recently that lipid metabolism disorders play an important role in carcinogenesis and development. As well, the role of lipids in disease is particularly relevant for bacterial infections, during which several lipid bacterial virulence factors are recognized by the human innate immune response, such as lipopolysaccharide in Gram-negative bacteria, lipoteichoic acid in Gram-positive bacteria, and lipoglycans in mycobacteria. Compared to nucleic acids and proteins, a complete analysis of the lipidome, which is the comprehensive characterization of different lipid families, is usually very challenging due to the heterogeneity of lipid classes and their intrinsic physicoproperties caused by variations in the constituents of each class. Understanding the chemical diversity of lipids is therefore crucial to understanding their biological relevance and, as a consequence, their use as potential biomarkers for non-infectious and infectious diseases. This mini-review exposes the current knowledge and limitations of the use of lipids as biomarkers of the top global killers which are cancer and bacterial infections.

Prevalence of extrapulmonary tuberculosis among people living with HIV/AIDS in sub-Saharan Africa: a systemic review and meta-analysis

BACKGROUND

The double burden of infectious diseases such as tuberculosis (TB) and HIV disproportionately affects Africa. Our objective was to summarize the prevalence of extrapulmonary TB (EPTB) among people living with HIV/AIDS (PLWHA) in sub-Saharan Africa (SSA).

METHODS

We searched PubMed and Google Scholar for studies done on the prevalence of EPTB among PLWHA which published in English from 1990 to 2017. We also searched bibliographic indices and browsed through reference lists of articles and journals. We critically appraised the quality of articles and abstracted the data with Joanna Briggs Institute (JBI) checklists. We used Review Manager Software (version 5.3) and Compressive Meta-analysis Software (version 2.2) for analysis. Finally, we summarized the effect estimate by using random-effects model and explored potential sources of heterogeneity by subgroup and sensitivity analyses. We assessed publication bias by funnel plot and statistical test. Finally, we used PRISMA format for reporting.

RESULTS

We included, in this review, 31 studies that fulfilled our inclusion criteria, with a total population of 28,659. The prevalence estimate of EPTB among PLWHA ranged from 6.4% (95% CI: 3.8, 9.0) to 36.8% (95% CI: 28.6, 45); random-effects pooled prevalence of EPTB among PLWHA was found to be 20% (95% CI: 17, 22; heterogeneity: τ2=0; χ2=509.09, degrees of freedom [df]=30, P<0.00001; I 2=94%). No evidence of publication bias was observed (P=0.44 for Egger's regression analysis and P=0.11 for Begg's rank correlation analysis).

CONCLUSION

We can conclude from our analyses that the prevalence of EPTB among PLWHA was high. It is necessary to give emphasis for EPTB, especially when screening TB among PLWHA, widening the spectrum of screening to include all EPTB sites in the countries with high EPTB and/or HIV prevalence in the general population.

Spatial and temporal clustering analysis of tuberculosis in the mainland of China at the prefecture level, 2005-2015

Background

Tuberculosis (TB) is still one of the most serious infectious diseases in the mainland of China. So it was urgent for the formulation of more effective measures to prevent and control it.

Methods

The data of reported TB cases in 340 prefectures from the mainland of China were extracted from the China Information System for Disease Control and Prevention (CISDCP) during January 2005 to December 2015. The Kulldorff’s retrospective space-time scan statistics was used to identify the temporal, spatial and spatio-temporal clusters of reported TB in the mainland of China by using the discrete Poisson probability model. Spatio-temporal clusters of sputum smear-positive (SS+) reported TB and sputum smear-negative (SS-) reported TB were also detected at the prefecture level.

Results

A total of 10 200 528 reported TB cases were collected from 2005 to 2015 in 340 prefectures, including 5 283 983 SS- TB cases and 4 631 734 SS + TB cases with specific sputum smear results, 284 811 cases without sputum smear test. Significantly TB clustering patterns in spatial, temporal and spatio-temporal were observed in this research. Results of the Kulldorff’s scan found twelve significant space-time clusters of reported TB. The most likely spatio-temporal cluster (RR = 3.27, P <  0.001) was mainly located in Xinjiang Uygur Autonomous Region of western China, covering five prefectures and clustering in the time frame from September 2012 to November 2015. The spatio-temporal clustering results of SS+ TB and SS- TB also showed the most likely clusters distributed in the western China. However, the clustering time of SS+ TB was concentrated before 2010 while SS- TB was mainly concentrated after 2010.

Conclusions

This study identified the time and region of TB, SS+ TB and SS- TB clustered easily in 340 prefectures in the mainland of China, which is helpful in prioritizing resource assignment in high-risk periods and high-risk areas, and to formulate powerful strategy to prevention and control TB.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0490-8) contains supplementary material, which is available to authorized users.

Recent technological advancements in tuberculosis diagnostics - A review

Early diagnosis and on-time effective treatment are indispensable for Tuberculosis (TB) control - a life threatening infectious communicable disease. The conventional techniques for diagnosing TB normally take two to three weeks. This delay in diagnosis and further increase in detection complexity due to the emerging risks of XDR-TB (Extensively drug Resistant-TB) and MDR-TB (Multidrug Resistant-TB) are evoking interest of researchers in the field of developing rapid TB detection techniques such as biosensing and other point-of-care (POC) techniques. Biosensing technologies along with the collaboration with nanotechnology have enormous potential to boost the MTB detection and for overall management in clinical diagnosis. A diverse range of portable, sensitive and rapid biosensors based on different signal transducer principles and with different biomarkers detection capabilities have been developed for TB detection in the early stages. Further, a lot of progress has been achieved over the years in developing various point-of-care diagnostic tools including non-molecular methods and molecular techniques. The objective of this study is to present a succinct review of the available TB detection techniques that are either in use or under development. The focus of this review is on the current developments occurred in nano-biosensing technologies. A synopsis of ameliorations in different non-molecular diagnostic tools and progress in the field of molecular techniques along with the role of emerging Lab-on-Chip technology for diagnosing and mitigating the TB consequences have also been presented.

Accuracy of different Xpert MTB/Rif implementation strategies in programmatic settings at the regional referral hospitals in Uganda: Evidence for country wide roll out

Background

Xpert MTB/RIF assay is a highly sensitive test for TB diagnosis, but still costly to most low-income countries. Several implementation strategies instead of frontline have been suggested; however with scarce data. We assessed accuracy of different Xpert MTB/RIF implementation strategies to inform national roll-out.

Methods

This was a cross-sectional study of 1,924 adult presumptive TB patients in five regional referral hospitals of Uganda. Two sputum samples were collected, one for fluorescent microscopy (FM) and Xpert MTB/RIF examined at the study site laboratories. The second sample was sent to the Uganda Supra National TB reference laboratory for culture using both Lowenstein Jensen (LJ) and liquid culture (MGIT). We compared the sensitivities of FM, Xpert MTB/RIF and the incremental sensitivity of Xpert MTB/RIF among patients negative on FM using LJ and/or MGIT as a reference standard.

Results

A total 1924 patients were enrolled of which 1596 (83%) patients had at least one laboratory result and 1083 respondents had a complete set of all the laboratory results. A total of 328 (30%) were TB positive on LJ and /or MGIT culture. The sensitivity of FM was n (%; 95% confidence interval) 246 (63.5%; 57.9–68.7) overall compared to 52 (55.4%; 44.1–66.3) among HIV positive individuals, while the sensitivity of Xpert MTB/RIF was 300 (76.2%; 71.7–80.7) and 69 (71.6%; 60.5–81.1) overall and among HIV positive individuals respectively. Overall incremental sensitivity of Xpert MTB/RIF was 60 (36.5%; 27.7–46.0) and 20 (41.7%; 25.5–59.2) among HIV positive individuals.

Conclusion

Xpert MTB/RIF has a higher sensitivity than FM both in general population and HIV positive population. Xpert MTB/RIF offers a significant increase in terms of diagnostic sensitivity even when it is deployed selectively i.e. among smear negative presumptive TB patients. Our results support frontline use of Xpert MTB/RIF assay in high HIV/TB prevalent countries. In settings with limited access, mechanisms to refer smear negative sputum samples to Xpert MTB/RIF hubs are recommended.

Widespread use of incorrect PCR ramp rate negatively impacts multidrug-resistant tuberculosis diagnosis (MTBDRplus)

The scale-up of rapid drug resistance testing for TB is a global priority. MTBDRplus is a WHO-endorsed multidrug-resistant (MDR)-TB PCR assay with suboptimal sensitivities and high indeterminate rates on smear-negative specimens. We hypothesised that widespread use of incorrect thermocycler ramp rate (speed of temperature change between cycles) impacts performance. A global sample of 72 laboratories was surveyed. We tested 107 sputa from Xpert MTB/RIF-positive patients and, separately, dilution series of bacilli, both at the manufacturer-recommended ramp rate (2.2 °C/s) and the most frequently reported incorrect ramp rate (4.0 °C/s). Mycobacterium tuberculosis-complex DNA (TUB-band)-detection, indeterminate results, accuracy, and inter-reader variability (dilution series only) were compared. 32 respondents did a median (IQR) of 41 (20-150) assays monthly. 78% used an incorrect ramp rate. On smear-negative sputa, 2.2 °C/s vs. 4.0 °C/s improved TUB-band positivity (42/55 vs. 32/55; p = 0.042) and indeterminate rates (1/42 vs. 5/32; p = 0.039). The actionable results (not TUB-negative or indeterminate; 41/55 vs. 28/55) hence improved by 21% (95% CI: 9-35%). Widespread use of incorrect ramp rate contributes to suboptimal MTBDRplus performance on smear-negative specimens and hence limits clinical utility. The number of diagnoses (and thus the number of smear-negative patients in whom DST is possible) will improve substantially after ramp rate correction.

Diagnosing tuberculosis in hospitalized HIV-infected individuals who cannot produce sputum: is urine lipoarabinomannan testing the answer?

Background

Up to one third of HIV-infected individuals with suspected TB are sputum-scarce. The Alere Determine™ TB LAM Ag lateral flow strip test can be used to diagnose TB in HIV-infected patients with advanced immunosuppression. However, how urine LAM testing should be incorporated into testing algorithms and in the context of specific patient sub-groups remains unclear.

Methods

This study represents a post hoc sub-group analysis of data from a randomized multi-center parent study. The study population consisted of hospitalized HIV-infected patients with suspected TB who were unable to produce sputum and who underwent urine LAM testing. The diagnostic utility of urine LAM for TB in this group was compared to the performance of urine LAM in patients who did produce a sputum sample in the parent study.

Results

There were a total of 187 and 2341 patients in the sputum-scarce and sputum-producing cohorts, respectively. 80 of the sputum-scarce patients underwent testing with urine LAM. In comparison to those who did produce sputum, sputum-scarce patients had a younger age, a lower Karnofsky performance score, and a lower weight and BMI at admission. A greater proportion of sputum-scarce patients were urine LAM positive, compared to those who were able to produce sputum (31% vs. 21%, p = 0.04). A higher proportion of sputum-scarce patients died within 8 weeks of admission (32% vs. 24%, p = 0.013). We inferred that 19% of HIV-infected sputum-scarce patients suspected of TB were diagnosed with tuberculosis by urine LAM testing, with an estimated positive predictive value of 63% (95% CI 43–82%).

Conclusions

Urine LAM testing can effectively identify tuberculosis in HIV-infected patients who are at a higher risk of mortality yet are unable to generate a sputum sample for diagnostic testing. Our findings support the use of urine LAM testing in sputum-scarce hospitalized HIV-infected patients, and its incorporation into diagnostic algorithms for this patient population.

Evaluation of a Urine-Based Rapid Molecular Diagnostic Test with Potential to Be Used at Point-of-Care for Pulmonary Tuberculosis: Cape Town Cohort

Tuberculosis (TB) diagnosis among sputum-scarce patients is time consuming. Thus, a nonsputum diagnostic alternative is urgently needed. The Mycobacterium tuberculosis-specific transrenal (Tr) DNA from urine is a potential target for TB diagnostics. In this study, a new urine-based Tr-DNA molecular assay was evaluated for diagnosis of pulmonary tuberculosis among 428 adults suspected of having pulmonary TB (164 HIV positive, 263 HIV negative) from Cape Town, South Africa. Tr-DNA was isolated from 4 mL of EDTA urine, and a rapid, double-stranded, primer-based PCR method was performed targeting the Mycobacterium tuberculosis-specific direct repeat region. Each Tr-DNA eluate was tested in triplicate using an automated molecular analyzer with controls included in each test. With liquid culture used as the gold standard, the Tr-DNA assay showed sensitivity of 42.9% (n = 75/175; 95% CI, 35.4%-50.5%) and specificity of 88.6% (n = 210/237; 95% CI, 83.9%-92.4%). Among HIV-infected patients with TB, sensitivity and specificity were 45.2% and 89.0%, respectively. The combination of smear microscopy and Tr-DNA increased the sensitivity to 83.8% (smear microscopy alone, 75.1%), with 96.6% specificity. This study indicates that Tr-DNA has a moderate specificity with low sensitivity for diagnosis of pulmonary TB. Despite low sensitivity, this diagnostic test may have potential in combination with smear microscopy to support TB diagnosis in HIV-endemic regions, where sputum-scarce patients are common.

Molecular diagnosis of suspected tuberculosis from archived smear slides from the Balimo region, Papua New Guinea

BACKGROUND

Tuberculosis (TB) is a serious health problem in Papua New Guinea (PNG) with an estimated 30000 new cases and 3800 deaths each year. In the Balimo region of the Western Province, diagnosis relies on clinical manifestations and on the microscopic detection of acid-fast bacilli (AFB) in sputum smears, a technique with limited sensitivity.

METHODS

A molecular diagnosis assay targeting DNA extracted from archived sputum smear slides collected from the Balimo region (2012-2014) was conducted, without the need for a viable culture. The presence of Mycobacterium sp on 1162 slides prepared from 345 sputum samples was assessed using a real-time PCR (qPCR) approach.

RESULTS

The qPCR technique identified the presence of mycobacteria in 35.4% of the smear slides and 59.7% of the tested sputum samples. Poor agreement was observed between the two diagnosis methods (smear AFB microscopy versus qPCR), with 100 AFB-positive sputum samples compared to 206 qPCR-positive sputum samples overall. Treatment was initiated in 90.2% of the smear-positive cases. Unnecessary treatment of 'false-positive' TB cases (AFB-negative/qPCR-negative) was very low (8.6%) and was even lower when the nine patients diagnosed with extrapulmonary TB were excluded from the analysis. However, the prevalence of false-negatives (AFB-negative/qPCR-positive) was high (28.5%).

CONCLUSIONS

Undetected smear-negative TB is occurring in the Balimo region of PNG, as well as some unnecessary empirical treatment. Molecular methods of diagnosis could greatly reduce the frequency of inappropriate clinical assessment, as well as providing point-of-care diagnosis. This may provide substantial patient and programmatic benefits, including lowering the economic burden on patients from rural areas seeking medical diagnosis in Balimo.