Point-of-care detection of lipoarabinomannan (LAM) in urine for diagnosis of HIV-associated tuberculosis: a state of the art review

Systematic, Point-of-Care Urine Lipoarabinomannan (Alere TB-LAM) Assay for Diagnosing Tuberculosis in Severely Immunocompromised HIV-Positive Ambulatory Patients

Point-of-care urine-lipoarabinomannan (LAM) Alere Determine TB-LAM assay has shown utility diagnosing tuberculosis (TB) in HIV-positive, severely immunocompromised, TB-symptomatic patients. We assessed LAM results in severely immunocompromised patients, who had LAM systematically performed at new or follow-up HIV consultations. This was a prospective, observational study on consecutive ambulatory, > 15-year-old HIV-positive patients with CD4 < 100 cells/µL in Mozambique. Clinical assessments and LAM were performed for all and microscopy, Xpert, sputum culture, and chest X-ray for LAM-positive participants. Patients were followed up for 6 months. Of 360 patients, half were ART-naive. Lipoarabinomannan positivity was 11.9% (43/360), higher among symptomatic patients compared with asymptomatic: 18.5% (30/162), and 6.6% (13/198), respectively, P = 0.001. Tuberculosis was bacteriologically confirmed in 6/35 LAM-positive patients (2 of them asymptomatic). Lipoarabinomannan positivity was associated with higher risk of mortality (adjusted odds ratio [aOR]: 4.6, 95% CI: 1.3–15.6, P = 0.015). Systematic urine-LAM allows for rapid TB treatment initiation in severely immunocompromised HIV ambulatory patients and identifies patients at a higher risk of death.

Diagnostic accuracy of a novel tuberculosis point-of-care urine lipoarabinomannan assay for people living with HIV: A meta-analysis of individual in- and outpatient data

BACKGROUND

Tuberculosis (TB) is the most common cause of death in people living with HIV (PLHIV), yet TB often goes undiagnosed since many patients are not able to produce a sputum specimen, and traditional diagnostics are costly or unavailable. A novel, rapid lateral flow assay, Fujifilm SILVAMP TB LAM (SILVAMP-LAM), detects the presence of TB lipoarabinomannan (LAM) in urine, and is substantially more sensitive for diagnosing TB in PLHIV than an earlier LAM assay (Alere Determine TB LAM lateral flow assay [LF-LAM]). Here, we present an individual participant data meta-analysis of the diagnostic accuracy of SILVAMP-LAM in adult PLHIV, including both published and unpublished data.

METHODS AND FINDINGS

Adult PLHIV (≥18 years) were assessed in 5 prospective cohort studies in South Africa (3 cohorts), Vietnam, and Ghana, carried out during 2012 to 2017. Of the 1,595 PLHIV who met eligibility criteria, the majority (61%) were inpatients, median age was 37 years (IQR 30-43), 43% had a CD4 count ≤ 100 cells/μl, and 35% were receiving antiretroviral therapy. Most participants (94%) had a positive WHO symptom screen for TB on enrollment, and 45% were diagnosed with microbiologically confirmed TB, using mycobacterial culture or Xpert MTB/RIF testing of sputum, urine, or blood. Previously published data from inpatients were combined with unpublished data from outpatients. Biobanked urine samples were tested, using blinded double reading, with SILVAMP-LAM and LF-LAM. Applying a microbiological reference standard for assessment of sensitivity, the overall sensitivity for TB detection was 70.7% (95% CI 59.0%-80.8%) for SILVAMP-LAM compared to 34.9% (95% CI 19.5%-50.9%) for LF-LAM. Using a composite reference standard (which included patients with both microbiologically confirmed as well as clinically diagnosed TB), SILVAMP-LAM sensitivity was 65.8% (95% CI 55.9%-74.6%), and that of LF-LAM 31.4% (95% CI 19.1%-43.7%). In patients with CD4 count ≤ 100 cells/μl, SILVAMP-LAM sensitivity was 87.1% (95% CI 79.3%-93.6%), compared to 56.0% (95% CI 43.9%-64.9%) for LF-LAM. In patients with CD4 count 101-200 cells/μl, SILVAMP-LAM sensitivity was 62.7% (95% CI 52.4%-71.9%), compared to 25.3% (95% CI 15.8%-34.9%) for LF-LAM. In those with CD4 count > 200 cells/μl, SILVAMP-LAM sensitivity was 43.9% (95% CI 34.3%-53.9%), compared to 10.9% (95% CI 5.2%-18.4%) for LF-LAM. Using a microbiological reference standard, the specificity of SILVAMP-LAM was 90.9% (95% CI 87.2%-93.7%), and that of LF-LAM 95.3% (95% CI 92.2%-97.7%). Limitations of this study include the use of biobanked, rather than fresh urine samples, and testing by skilled laboratory technicians in research laboratories, rather than at the point of care.

CONCLUSIONS

In this study, we found that SILVAMP-LAM identified a substantially higher proportion of TB patients in PLHIV than LF-LAM. The sensitivity of SILVAMP-LAM was highest in patients with CD4 count ≤ 100 cells/μl. Further work is needed to demonstrate accuracy when implemented as a point-of-care test.

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.

Multidrug-Resistant Tuberculosis in Patients with Human Immunodeficiency Virus. Management Considerations within High-resourced Settings

The management of multidrug-resistant tuberculosis (MDR TB) is notably complex among patients with human immunodeficiency virus (HIV). TB treatment recommendations typically include very little information specific to HIV and MDR TB, which often is derived from clinical trials conducted in low-resource settings. Mortality rates among patients with HIV and MDR TB remain high. We reviewed the published literature and recommendations to synthesize possible patient management approaches demonstrated to improve treatment outcomes in high-resourced countries for patients with MDR TB and HIV. Approaches to diagnostic testing, impact and timing of antiretroviral therapy on mortality, anti-MDR TB and antiretroviral drug interactions, and the potential role for short-course MDR TB therapy are examined. The combination of antiretroviral therapy with expanded TB drug therapy, along with the management of immune reconstitution inflammatory syndrome, other potential HIV-associated opportunistic diseases, and drug toxicities, necessitate an integrated multidisciplinary patient care approach using public health case management and provider expertise in drug-resistant TB and HIV management.

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.

Point-Of-Care Urine LAM Tests for Tuberculosis Diagnosis: A Status Update

Most diagnostic tests for tuberculosis (TB) rely on sputum samples, which are difficult to obtain and have low sensitivity in immunocompromised patients, patients with disseminated TB, and children, delaying treatment initiation. The World Health Organization (WHO) calls for the development of a rapid, biomarker-based, non-sputum test capable of detecting all forms of TB at the point-of-care to enable immediate treatment initiation. Lipoarabinomannan (LAM) is the only WHO-endorsed TB biomarker that can be detected in urine, an easily collected sample. This status update discusses the characteristics of LAM as a biomarker, describes the performance of first-generation urine LAM tests and reasons for slow uptake, and presents considerations for developing the next generation of more sensitive and impactful tests. Next-generation urine LAM tests have the potential to reach adult and pediatric patients regardless of HIV status or site of infection and facilitate global TB control. Implementation and scale-up of existing LAM tests and development of next-generation assays should be prioritized.

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.

Lateral flow urine lipoarabinomannan assay for detecting active tuberculosis in people living with HIV

BACKGROUND

The lateral flow urine lipoarabinomannan (LF-LAM) assay Alere Determine™ TB LAM Ag is recommended by the World Health Organization (WHO) to help detect active tuberculosis in HIV-positive people with severe HIV disease. This review update asks the question, "does new evidence justify the use of LF-LAM in a broader group of people?", and is part of the WHO process for updating guidance on the use of LF-LAM.

OBJECTIVES

To assess the accuracy of LF-LAM for the diagnosis of active tuberculosis among HIV-positive adults with signs and symptoms of tuberculosis (symptomatic participants) and among HIV-positive adults irrespective of signs and symptoms of tuberculosis (unselected participants not assessed for tuberculosis signs and symptoms).The proposed role for LF-LAM is as an add on to clinical judgement and with other tests to assist in diagnosing tuberculosis.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; MEDLINE, Embase, Science Citation Index, Web of Science, Latin American Caribbean Health Sciences Literature, Scopus, the WHO International Clinical Trials Registry Platform, the International Standard Randomized Controlled Trial Number Registry, and ProQuest, without language restriction to 11 May 2018.

SELECTION CRITERIA

Randomized trials, cross-sectional, and observational cohort studies that evaluated LF-LAM for active tuberculosis (pulmonary and extrapulmonary) in HIV-positive adults. We included studies that used the manufacturer's recommended threshold for test positivity, either the updated reference card with four bands (grade 1 of 4) or the corresponding prior reference card grade with five bands (grade 2 of 5). The reference standard was culture or nucleic acid amplification test from any body site (microbiological). We considered a higher quality reference standard to be one in which two or more specimen types were evaluated for tuberculosis diagnosis and a lower quality reference standard to be one in which only one specimen type was evaluated.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data using a standardized form and REDCap electronic data capture tools. We appraised the quality of studies using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool and performed meta-analyses to estimate pooled sensitivity and specificity using a bivariate random-effects model and a Bayesian approach. We analyzed studies enrolling strictly symptomatic participants separately from those enrolling unselected participants. We investigated pre-defined sources of heterogeneity including the influence of CD4 count and clinical setting on the accuracy estimates. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 15 unique studies (nine new studies and six studies from the original review that met the inclusion criteria): eight studies among symptomatic adults and seven studies among unselected adults. All studies were conducted in low- or middle-income countries. Risk of bias was high in the patient selection and reference standard domains, mainly because studies excluded participants unable to produce sputum and used a lower quality reference standard.Participants with tuberculosis symptomsLF-LAM pooled sensitivity (95% credible interval (CrI) ) was 42% (31% to 55%) (moderate-certainty evidence) and pooled specificity was 91% (85% to 95%) (very low-certainty evidence), (8 studies, 3449 participants, 37% with tuberculosis).For a population of 1000 people where 300 have microbiologically-confirmed tuberculosis, the utilization of LF-LAM would result in: 189 to be LF-LAM positive: of these, 63 (33%) would not have tuberculosis (false-positives); and 811 to be LF-LAM negative: of these, 174 (21%) would have tuberculosis (false-negatives).By clinical setting, pooled sensitivity was 52% (40% to 64%) among inpatients versus 29% (17% to 47%) among outpatients; and pooled specificity was 87% (78% to 93%) among inpatients versus 96% (91% to 99%) among outpatients. Stratified by CD4 cell count, pooled sensitivity increased, and specificity decreased with lower CD4 cell count.Unselected participants not assessed for signs and symptoms of tuberculosisLF-LAM pooled sensitivity was 35% (22% to 50%), (moderate-certainty evidence) and pooled specificity was 95% (89% to 96%), (low-certainty evidence), (7 studies, 3365 participants, 13% with tuberculosis).For a population of 1000 people where 100 have microbiologically-confirmed tuberculosis, the utilization of LF-LAM would result in: 80 to be LF-LAM positive: of these, 45 (56%) would not have tuberculosis (false-positives); and 920 to be LF-LAM negative: of these, 65 (7%) would have tuberculosis (false-negatives).By clinical setting, pooled sensitivity was 62% (41% to 83%) among inpatients versus 31% (18% to 47%) among outpatients; pooled specificity was 84% (48% to 96%) among inpatients versus 95% (87% to 99%) among outpatients. Stratified by CD4 cell count, pooled sensitivity increased, and specificity decreased with lower CD4 cell count.

AUTHORS' CONCLUSIONS

We found that LF-LAM has a sensitivity of 42% to diagnose tuberculosis in HIV-positive individuals with tuberculosis symptoms and 35% in HIV-positive individuals not assessed for tuberculosis symptoms, consistent with findings reported previously. Regardless of how people are enrolled, sensitivity is higher in inpatients and those with lower CD4 cell, but a concomitant lower specificity. As a simple point-of-care test that does not depend upon sputum evaluation, LF-LAM may assist with the diagnosis of tuberculosis, particularly when a sputum specimen cannot be produced.

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.

Urinary LAM grade, culture positivity, and mortality among HIV-infected South African out-patients

SETTING

Four ambulatory clinics in Durban, South Africa.

OBJECTIVE

To test the relationships of patient characteristics, time to mycobacterial culture positivity, and mortality with urinary lipoarabinomannan (LAM) grade category.

DESIGN

Newly diagnosed human immunodeficiency virus (HIV) infected adults were screened for tuberculosis (TB) using sputum culture, tested for urinary LAM, and followed for up to 12 months. We performed multivariable ordinal logistic regression of risk factors for low (1 or 2) or high (3, 4, or 5) LAM grade. We used adjusted Cox regression models to determine the hazard ratios of time to culture positivity and death.

RESULTS

Among 683 HIV-infected adults, median CD4 count was 215 cells/mm³ (interquartile range 86-361 cells/mm³), 17% had culture-confirmed TB, and 11% died during follow-up. Smoking, tachycardia (pulse > 100 beats/minute), CD4 count < 100 cells/mm³, and TB culture positivity were each associated with higher LAM grade. In multivariate models, a high urine LAM grade was associated with four-fold increased hazard of culture positivity (P = 0.001) and two-fold increased hazard of mortality (P = 0.02). Among patients treated for TB, these associations were no longer statistically significant.

CONCLUSION

In this population, a higher urine LAM grade was associated with shorter time to culture positivity and mortality; however, these associations were not present for those starting anti-tuberculosis treatment.

Accuracy and incremental yield of urine Xpert MTB/RIF Ultra versus Determine TB-LAM for diagnosis of pulmonary tuberculosis

The performance of urine Xpert MTB/RIF Ultra (Xpert Ultra) for pulmonary TB diagnosis is unknown. HIV-positive and HIV-negative adults were enrolled at two health facilities in Kampala, Uganda. We compared the accuracy of urine Xpert Ultra and Determine TB-LAM in reference to sputum-based testing (positive Xpert MTB/RIF or culture), and assessed incremental yield. Urine Xpert Ultra had low sensitivity (17.2%, 95% CI 12.3-23.2) but high specificity (98.1%, 95% CI 94.4-99.6). Sensitivity reached 50.0% (95% CI 28.2-71.8) among HIV-positive patients with CD4 <100 cells/μL. Compared to Determine TB-LAM, urine Xpert Ultra was 9.4% (95% CI 3.8-14.9, P = 0.01) more sensitive, and 17.2% (95% CI 4.5-29.8, P = 0.01) more sensitive among HIV-positive patients. However, the incremental sensitivity of urine Xpert Ultra relative to sputum Xpert MTB/RIF was only 1% (95% CI -0.9 to 2.8). Urine Xpert Ultra could be an alternative for patients with advanced HIV infection unable to produce sputum.

Urine lipoarabinomannan (LAM) and antimicrobial usage in seriously-ill HIV-infected patients with sputum smear-negative pulmonary tuberculosis

Background

Based on current WHO guidelines, hospitalized tuberculosis (TB) and HIV co-infected patients with CD4 count <100 cells/mm³ who are urine lipoarabinomannan (LAM) positive should be initiated on TB treatment. This recommendation is conditional, and data are limited in sputum smear-negative patients from TB endemic countries where the LAM test is largely inaccessible. Other potential benefits of LAM, including reduction in antibiotic usage have, hitherto, not been explored.

Methods

We consecutively enrolled newly-admitted seriously-ill HIV-infected patients (n=187) with suspected TB from three hospitals in KwaZulu-Natal, South Africa. All patients were empirically treated for TB as per the WHO 2007 smear-negative TB algorithm (patients untreated for TB were not recruited). Bio-banked urine, donated prior to anti-TB treatment, was tested for TB-infection using a commercially available LAM-ELISA test. TB sputum and blood cultures were performed.

Results

Data from 156 patients containing CD4 count, urine-LAM, sputum and blood culture results were analysed. Mean age was 37 years, median CD4-count was 75 cells/mm³ [interquartile range (IQR), 34-169 cells/mm³], 54/156 (34.6%) were sputum culture-positive, 12/54 (22.2%) blood-culture positive, and 53/156 (34.0%) LAM-positive. Thus, LAM sensitivity was 55.6% (30/54). The study design did not allow for calculation of specificity. Urine-LAM positivity was associated with low CD4 count (P=0.002). Ninety-point-six percent (48/53) of LAM-positive patients received antibiotics [15/48 (31.3%), 23/48 (47.9%) and 10/48 (20.8%) received one, two or three different antibiotics respectively], while the duration of antibiotic therapy was more than 5 days in 26 of 46 (56.5%) patients.

Conclusions

Urine LAM testing in sputum smear-negative severely-ill hospitalized patients with TB-HIV co-infection and advanced immunosuppression, offered an immediate rule-in diagnosis in one-third of empirically treated patients. Moreover, LAM, by providing a rapid alternative diagnosis, could potentially reduce antibiotic overusage in such patients thereby reducing health-care costs and facilitating antibiotic stewardship.

Does Disseminated Nontuberculous Mycobacterial Disease Cause False-Positive Determine TB-LAM Lateral Flow Assay Results? A Retrospective Review

We retrospectively reviewed the Determine TB-LAM lateral flow assay (LF-LAM) results among human immunodeficiency virus-infected patients with disseminated nontuberculous mycobacterial (NTM) disease. LF-LAM was positive in 19 of 21 patients without evidence of tuberculosis (TB) coinfection. Although TB-NTM coinfection may have been underdiagnosed, our results suggest that disseminated NTM disease may cause false-positive LF-LAM results.

Tuberculosis

Tuberculosis remains the leading cause of death from an infectious disease among adults worldwide, with more than 10 million people becoming newly sick from tuberculosis each year. Advances in diagnosis, including the use of rapid molecular testing and whole-genome sequencing in both sputum and non-sputum samples, could change this situation. Although little has changed in the treatment of drug-susceptible tuberculosis, data on increased efficacy with new and repurposed drugs have led WHO to recommend all-oral therapy for drug-resistant tuberculosis for the first time ever in 2018. Studies have shown that shorter latent tuberculosis prevention regimens containing rifampicin or rifapentine are as effective as longer, isoniazid-based regimens, and there is a promising vaccine candidate to prevent the progression of infection to the disease. But new tools alone are not sufficient. Advances must be made in providing high-quality, people-centred care for tuberculosis. Renewed political will, coupled with improved access to quality care, could relegate the morbidity, mortality, and stigma long associated with tuberculosis, to the past.

Diagnostic value of the urine lipoarabinomannan assay in HIV-positive, ambulatory patients with CD4 below 200 cells/μl in 2 low-resource settings: A prospective observational study

BACKGROUND

Current guidelines recommend the use of the lateral flow urine lipoarabinomannan assay (LAM) in HIV-positive, ambulatory patients with signs and symptoms of tuberculosis (TB) only if they are seriously ill or have CD4 count ≤ 100 cells/μl. We assessed the diagnostic yield of including LAM in TB diagnostic algorithms in HIV-positive, ambulatory patients with CD4 < 200 cells/μl, as well as the risk of mortality in LAM-positive patients who were not diagnosed using other diagnostic tools and not treated for TB.

METHODS AND FINDINGS

We conducted a prospective observational study including HIV-positive adult patients with signs and symptoms of TB and CD4 < 200 cells/μl attending 6 health facilities in Malawi and Mozambique. Patients were included consecutively from 18 September 2015 to 27 October 2016 in Malawi and from 3 December 2014 to 22 August 2016 in Mozambique. All patients had a clinical exam and LAM, chest X-ray, sputum microscopy, and Xpert MTB/RIF assay (Xpert) requested. Culture in sputum was done for a subset of patients. The diagnostic yield was defined as the proportion of patients with a positive assay result among those with laboratory-confirmed TB. For the 456 patients included in the study, the median age was 36 years (IQR 31-43) and the median CD4 count was 50 cells/μl (IQR 21-108). Forty-five percent (205/456) of the patients had laboratory-confirmed TB. The diagnostic yields of LAM, microscopy, and Xpert were 82.4% (169/205), 33.7% (69/205), and 40.0% (84/205), respectively. In total, 50.2% (103/205) of the patients with laboratory-confirmed TB were diagnosed only through LAM. Overall, the use of LAM in diagnostic algorithms increased the yield of algorithms with microscopy and with Xpert by 38.0% (78/205) and 34.6% (71/205), respectively, and, specifically among patients with CD4 100-199 cells/μl, by 27.5% (14/51) and 29.4% (15/51), respectively. LAM-positive patients not diagnosed through other tools and not treated for TB had a significantly higher risk of mortality than LAM-positive patients who received treatment (adjusted risk ratio 2.57, 95% CI 1.27-5.19, p = 0.009). Although the TB diagnostic conditions in the study sites were similar to those in other resource-limited settings, the added value of LAM may depend on the availability of microscopy or Xpert results.

CONCLUSIONS

LAM has diagnostic value for identifying TB in HIV-positive patients with signs and symptoms of TB and advanced immunodeficiency, including those with a CD4 count of 100-199 cells/μl. In this study, the use of LAM enabled the diagnosis of TB in half of the patients with confirmed TB disease; without LAM, these patients would have been missed. The rapid identification and treatment of TB enabled by LAM may decrease overall mortality risk for these patients.

Lateral Flow Urine Lipoarabinomannan Assay for Diagnosis of Active Tuberculosis in Adults With Human Immunodeficiency Virus Infection: A Prospective Cohort Study

Background

Detection of mycobacterial lipoarabinomannan antigen in urine has emerged as a potential point-of-care test for diagnosis of tuberculosis. This study aimed to evaluate the accuracy of the lateral flow urine lipoarabinomannan (LF-LAM) assay for diagnosis of active tuberculosis among Thai adults with advanced human immunodeficiency virus (HIV) infection.

Methods

HIV-infected adult patients with CD4 cell counts ≤200/μL and symptoms suggestive of active tuberculosis were prospectively recruited from both inpatient and outpatient settings at Siriraj Hospital and Chonburi Hospital in Thailand during the study period from December 2015 to March 2017. Freshly collected urine samples were applied to the Alere Determine TB LAM Ag test strip using a grade 1 cutoff, according to the manufacturer’s grading system. The diagnostic accuracy of the LF-LAM test was assessed against a microbiological reference standard (definite tuberculosis) or a composite reference standard (definite and probable tuberculosis).

Results

Of the 280 patients who were included, 72 (25.7%) had definite and 65 (23.2%) had probable tuberculosis. Among patients with definite tuberculosis, the LF-LAM test yielded a sensitivity of 75.0% and a specificity of 76.0%. It had the highest sensitivity (90.5%) in HIV-infected patients with CD4 cell counts <50/μL. It yielded a lower sensitivity (61.3%) but a higher specificity (86.0%) when compared with the composite reference standard. Among the 20 patients (14%) with false-positive results, strong band intensity was observed mostly in Mycobacterium avium complex infections. An incremental sensitivity of 11% was observed with use of acid-fast bacilli sputum smear or LF-LAM testing, compared with LF-LAM testing alone.

Conclusions

The LF-LAM test performed well in the diagnosis of active tuberculosis in selected patients with more advanced tuberculosis and coexisting HIV disease.

Broad-spectrum capture of clinical pathogens using engineered Fc-mannose-binding lectin enhanced by antibiotic treatment

Background: Fc-mannose-binding lectin (FcMBL), an engineered version of the blood opsonin MBL that contains the carbohydrate recognition domain (CRD) and flexible neck regions of MBL fused to the Fc portion of human IgG1, has been shown to bind various microbes and pathogen-associated molecular patterns (PAMPs). FcMBL has also been used to create an enzyme-linked lectin sorbent assay (ELLecSA) for use as a rapid (<1 h) diagnostic of bloodstream infections. Methods: Here we extended this work by using the ELLecSA to test FcMBL's ability to bind to more than 190 different isolates from over 95 different pathogen species. Results: FcMBL bound to 85% of the isolates and 97 of the 112 (87%) different pathogen species tested, including bacteria, fungi, viral antigens and parasites. FcMBL also bound to PAMPs including, lipopolysaccharide endotoxin (LPS) and lipoteichoic acid (LTA) from Gram-negative and Gram-positive bacteria, as well as lipoarabinomannan (LAM) and phosphatidylinositol mannoside 6 (PIM 6) from Mycobacterium tuberculosis. Conclusions: The efficiency of pathogen detection and variation between binding of different strains of the same species could be improved by treating the bacteria with antibiotics, or mechanical disruption using a bead mill, prior to FcMBL capture to reveal previously concealed binding sites within the bacterial cell wall. As FcMBL can bind to pathogens and PAMPs in urine as well as blood, its broad-binding capability could be leveraged to develop a variety of clinically relevant technologies, including infectious disease diagnostics, therapeutics, and vaccines.

Detection of the tuberculosis biomarker mannose-capped lipoarabinomannan in human serum: Impact of sample pretreatment with perchloric acid

The development of an accurate and rapid diagnostic test for tuberculosis (TB) to use at point of need is vital to efforts aimed at reducing the global burden from this disease. This paper builds on our previous studies of mannose-capped lipoarabinomannan (ManLAM) as a serum biomarker for active TB infection by means of a heterogeneous immunoassay. That work found that complexation with components in serum (e.g., proteins) sterically hindered the capture and/or labeling of ManLAM in an immunoassay at levels <10 ng mL-1, compromising the clinical utility of this biomarker for detection of active TB infection. We also showed that the acidification of ManLAM-containing serum samples with perchloric acid improved the detectability of ManLAM by 250× by complex disruption when compared to measurements of untreated serum. The present study examined what effects the PCA treatment of serum samples may have on the recovery and structural integrity of ManLAM, owing to its potential susceptibility to acid hydrolysis. Recovery was assessed with an enzyme-linked immunosorbent assay (ELISA). The possible impact of acid hydrolysis on the ManLAM structure was investigated by gas chromatography-mass spectrometry and carbohydrate chemical degradation methods. The ELISA study indicated that while the signal strength for ManLAM in the serum spike-in experiments was significantly stronger after PCA pretreatment when compared to untreated human serum, it was only ∼20% of the ManLAM measured in physiological buffer. This loss in detectability was shown by structural analysis to arise mainly from the acid-induced degradation of the arabinan domains of ManLAM that are targeted by antibodies used for antigen capture and/or tagging. The implications of these findings in terms of the detection of this important biomarker for TB are also discussed.

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.

A Novel Sensitive Immunoassay Targeting the 5-Methylthio-d-Xylofuranose-Lipoarabinomannan Epitope Meets the WHO's Performance Target for Tuberculosis Diagnosis

The only currently commercialized point-of-care assay for tuberculosis (TB) that measures lipoarabinomannan (LAM) in urine (Alere LF-LAM) has insufficient sensitivity. We evaluated the potential of 100 novel monoclonal antibody pairs targeting a variety of LAM epitopes on a sensitive electrochemiluminescence platform to improve the diagnostic accuracy.

The only currently commercialized point-of-care assay for tuberculosis (TB) that measures lipoarabinomannan (LAM) in urine (Alere LF-LAM) has insufficient sensitivity. We evaluated the potential of 100 novel monoclonal antibody pairs targeting a variety of LAM epitopes on a sensitive electrochemiluminescence platform to improve the diagnostic accuracy. In the screening, many antibody pairs showed high reactivity to purified LAM but performed poorly at detecting urinary LAM in clinical samples, suggesting differences in antigen structure and immunoreactivity of the different LAM sources. The 12 best antibody pairs from the screening were tested in a retrospective case-control study with urine samples from 75 adults with presumptive TB. The best antibody pair reached femtomolar analytical sensitivity for LAM detection and an overall clinical sensitivity of 93% (confidence interval [CI], 80% to 97%) and specificity of 97% (CI, 85% to 100%). Importantly, in HIV-negative subjects positive for TB by sputum smear microscopy, the test achieved a sensitivity of 80% (CI, 55% to 93%). This compares to an overall sensitivity of 33% (CI, 20% to 48%) of the Alere LF-LAM and a sensitivity of 13% (CI, 4% to 38%) in HIV-negative subjects in the same sample set. The capture antibody targets a unique 5-methylthio-d-xylofuranose (MTX)-dependent epitope in LAM that is specific to the Mycobacterium tuberculosis complex and shows no cross-reactivity with fast-growing mycobacteria or other bacteria. The present study provides evidence that improved assay methods and reagents lead to increased diagnostic accuracy. The results of this work have informed the development of a sensitive and specific novel LAM point-of-care assay with the aim to meet the WHO's performance target for TB diagnosis.

Exhaled human breath analysis in active pulmonary tuberculosis diagnostics by comprehensive gas chromatography-mass spectrometry and chemometric techniques

Tuberculosis (TB) is the deadliest infectious disease, and yet accurate diagnostics for the disease are unavailable for many subpopulations. In this study, we investigate the possibility of using human breath for the diagnosis of active TB among TB suspect patients, considering also several risk factors for TB for smokers and those with human immunodeficiency virus (HIV). The analysis of exhaled breath, as an alternative to sputum-dependent tests, has the potential to provide a simple, fast, non-invasive, and readily available diagnostic service that could positively change TB detection. A total of 50 individuals from a clinic in South Africa were included in this pilot study. Human breath has been investigated in the setting of active TB using the thermal desorption-comprehensive two-dimensional gas chromatography-time of flight mass spectrometry methodology and chemometric techniques. From the entire spectrum of volatile metabolites in breath, three machine learning algorithms (support vector machines, partial least squares discriminant analysis, and random forest) to select discriminatory volatile molecules that could potentially be useful for active TB diagnosis were employed. Random forest showed the best overall performance, with sensitivities of 0.82 and 1.00 and specificities of 0.92 and 0.60 in the training and test data respectively. Unsupervised analysis of the compounds implicated by these algorithms suggests that they provide important information to cluster active TB from other patients. These results suggest that developing a non-invasive diagnostic for active TB using patient breath is a potentially rich avenue of research, including among patients with HIV comorbidities.

Label-Free and Real-Time Detection of Tuberculosis in Human Urine Samples Using a Nanophotonic Point-of-Care Platform

Tuberculosis (TB) is the leading global cause of death from a single infectious agent. Registered incidence rates are low, especially in low-resource countries with weak health systems, due to the disadvantages of current diagnostic techniques. A major effort is directed to develop a point-of-care (POC) platform to reduce TB deaths with a prompt and reliable low-cost technique. In the frame of the European POCKET Project, a novel POC platform for the direct and noninvasive detection of TB in human urine was developed. The photonic sensor chip is integrated in a disposable cartridge and is based on a highly sensitive Mach-Zehnder Interferometer (MZI) transducer combined with an on-chip spectral filter. The required elements for the readout are integrated in an instrument prototype, which allows real-time monitoring and data processing. In this work, the novel POC platform has been employed for the direct detection of lipoarabinomannan (LAM), a lipopolysaccharide found in the mycobacterium cell wall. After the optimization of several parameters, a limit of detection of 475 pg/mL (27.14 pM) was achieved using a direct immunoassay in undiluted human urine in less than 15 min. A final validation of the technique was performed using 20 clinical samples from TB patients and healthy donors, allowing the detection of TB in people regardless of HIV coinfection. The results show excellent correlation to those obtained with standard techniques. These promising results demonstrate the high sensitivity, specificity and applicability of our novel POC platform, which could be used during routine check-ups in developing countries.

Detection of Lipomannan in Cattle Infected with Bovine Tuberculosis

Early and rapid detection of bovine tuberculosis (bTB) is critical to controlling the spread of this disease in cattle and other animals. In this study, we demonstrate the development of an immunoassay for the direct detection of the bovine bTB biomarker, lipomannan (LM) in serum using a waveguide-based optical biosensor. We apply an ultra-sensitive detection strategy developed by our team, termed lipoprotein capture, that exploits the pull-down of high-density lipoprotein (HDL) nanodiscs from cattle blood that allows for the recovery and detection of associated LM. We also profile the change in the expression of these TB biomarkers as a function of time from a small set of samples collected from studies of bovine TB-infected cattle. We demonstrate for the first time the direct detection of bovine LM in serum, and clearly show that the biomarker is expressed in detectable concentrations during the entire course of the infection.

Tuberculosis Case Finding With Combined Rapid Point-of-Care Assays (Xpert MTB/RIF and Determine TB LAM) in HIV-Positive Individuals Starting Antiretroviral Therapy in Mozambique

Background

Tuberculosis is a major health concern in several countries, and effective diagnostic algorithms for use in human immunodeficiency virus (HIV)-positive patients are urgently needed.

Methods

At prescription of antiretroviral therapy, all patients in 3 Mozambican health centers were screened for tuberculosis, with a combined approach: World Health Organization (WHO) 4-symptom screening (fever, cough, night sweats, and weight loss), a rapid test detecting mycobacterial lipoarabinomannan in urine (Determine TB LAM), and a molecular assay performed on a sputum sample (Xpert MTB/RIF; repeated if first result was negative). Patients with positive LAM or Xpert MTB/RIF results were referred for tuberculosis treatment.

Results

Among 972 patients with a complete diagnostic algorithm (58.5% female; median CD4 cell count, 278/μL; WHO HIV stage I, 66.8%), 98 (10.1%) tested positive with Xpert (90, 9.3%) or LAM (34, 3.5%) assays. Compared with a single-test Xpert strategy, dual Xpert tests improved case finding by 21.6%, LAM testing alone improved it by 13.5%, and dual Xpert tests plus LAM testing improved it by 32.4%. Rifampicin resistance in Xpert-positive patients was infrequent (2.5%). Among patients with positive results, 22 of 98 (22.4%) had no symptoms at WHO 4-symptom screening. Patients with tuberculosis diagnosed had significantly lower CD4 cell counts and hemoglobin levels, more advanced WHO stage, and higher HIV RNA levels. Fifteen (15.3%) did not start tuberculosis treatment, mostly owing to rapidly deteriorating clinical conditions or logistical constraints. The median interval between start of the diagnostic algorithm and start of tuberculosis treatment was 7 days.

Conclusions

The prevalence of tuberculosis among Mozambican HIV-positive patients starting antiretroviral therapy was 10%, with limited rifampicin resistance. Use of combined point-of-care tests increased case finding, with a short time to treatment. Interventions are needed to remove logistical barriers and prevent presentation in very advanced HIV/tuberculosis disease.

Detection of lipoarabinomannan in urine and serum of HIV-positive and HIV-negative TB suspects using an improved capture-enzyme linked immuno absorbent assay and gas chromatography/mass spectrometry

TB diagnosis and treatment monitoring in resource limited regions rely heavily on serial sputum smear microscopy and bacterial culture. These microbiological methods are time-consuming, expensive and lack adequate sensitivity. The WHO states that improved TB diagnosis and treatment is imperative to achieve an end to the TB epidemic by 2030. Commercially available lipoarabinomannan (LAM) detection tools perform at low sensitivity that are highly dependent on the underlying immunological status of the patient; those with advanced HIV infection perform well. In this study, we have applied two novel strategies towards the sensitive diagnosis of TB infection based on LAM: Capture ELISA to detect LAM in paired urine and serum samples using murine and human monoclonal antibodies, essentially relying on LAM as an 'immuno-marker'; and, secondly, detection of α-d-arabinofuranose and tuberculostearic acid (TBSA)- 'chemical-markers' unique to mycobacterial cell wall polysaccharides/lipoglycans by our recently developed gas chromatography/mass spectrometry (GC/MS) method. Blinded urine specimens, with microbiologically confirmed active pulmonary TB or non TB (HIV+/HIV-) were tested by the aforementioned assays. LAM in patient urine was detected in a concentration range of 3-28 ng/mL based on GC/MS detection of the two LAM-surrogates, d-arabinose and tuberculostearic acid (TBSA) correctly classifying TB status with sensitivity > 99% and specificity = 84%. The ELISA assay had high sensitivity (98%) and specificity (92%) and the results were in agreement with GC/MS analysis. Both tests performed well in their present form particularly for HIV-negative/TB-positive urine samples. Among the HIV+/TB+ samples, 52% were found to have >10 ng/mL urinary LAM. The detected amounts of LAM present in the urine samples also appears to be associated with the gradation of the sputum smear, linking elevated LAM levels with higher mycobacterial burden (odds ratio = 1.08-1.43; p = 0.002). In this small set, ELISA was also applied to parallel serum samples confirming that serum could be an additional reservoir for developing a LAM-based immunoassay for diagnosis of TB.

Disparities in model-based cost-effectiveness analyses of tuberculosis diagnosis: A systematic review

Background

Structural approach disparities were minimally addressed in past systematic reviews of model-based cost-effectiveness analyses addressing Tuberculosis management strategies. This review aimed to identify the structural approach disparities in model-based cost-effectiveness analysis studies addressing Tuberculosis diagnosis and describe potential hazards caused by those disparities.

Methods

A systematic search to identify studies published before October 2015 was performed in five electronic databases. After removal of duplication, studies’ titles and abstracts were screened based on predetermined criteria. The full texts of potentially relevant studies were subsequently screened and excluded when they did not address active pulmonary Tuberculosis diagnosis. Quality of the studies was assessed using the “Philips’ checklist.” Various data regarding general information, cost-effectiveness results, and disease modeling were extracted using standardized data extraction forms. Data pertaining to models’ structural approaches were compared and analyzed qualitatively for their applicability in various study settings, as well as their potential influence on main outcomes and cost-effectiveness conclusion.

Results

A total of 27 studies were included in the review. Most studies utilized a static model, which could underestimate the cost-effectiveness of the diagnostic tools strategies, due to the omission of indirect diagnosis effects, i.e. transmission reduction. A few structural assumption disparities were found in the dynamic models. Extensive disparities were found in the static models, consisting of varying structural assumptions regarding treatment outcomes, clinical diagnosis and empirical treatment, inpatient discharge decision, and re-diagnosis of false negative patients.

Conclusion

In cost-effectiveness analysis studies addressing active pulmonary Tuberculosis diagnosis, models showed numerous disparities in their structural approaches. Several structural approaches could be inapplicable in certain settings. Furthermore, they could contribute to under- or overestimation of the cost-effectiveness of the diagnosis tools or strategies. They could thus lead to ambiguities and difficulties when interpreting a study result. A set of recommendations is proposed to manage issues related to these structural disparities.

Needle lost in the haystack: multiple reaction monitoring fails to detect Treponema pallidum candidate protein biomarkers in plasma and urine samples from individuals with syphilis

Background: Current syphilis diagnostic strategies are lacking a sensitive manner of directly detecting Treponema pallidum antigens. A diagnostic test that could directly detect T. pallidum antigens in individuals with syphilis would be of considerable clinical utility, especially for the diagnosis of reinfections and for post-treatment serological follow-up.

Methods: In this study, 11 candidate T. pallidum biomarker proteins were chosen according to their physiochemical characteristics, T. pallidum specificity and predicted abundance. Thirty isotopically labelled proteotypic surrogate peptides (hPTPs) were synthesized and incorporated into a scheduled multiple reaction monitoring assay. Protein extracts from undepleted/unenriched plasma (N = 18) and urine (N = 4) samples from 18 individuals with syphilis in various clinical stages were tryptically digested, spiked with the hPTP mixture and analysed with a triple quadruple mass spectrometer.

Results: No endogenous PTPs corresponding to the eleven candidate biomarkers were detected in any samples analysed. To estimate the Limit of Detection (LOD) of a comparably sensitive mass spectrometer (LTQ-Orbitrap), two dilution series of rabbit cultured purified T. pallidum were prepared in PBS. Polyclonal anti- T. pallidum antibodies coupled to magnetic Dynabeads were used to enrich one sample series; no LOD improvement was found compared to the unenriched series. The estimated LOD of MS instruments is 300 T. pallidum/ml in PBS.

Conclusions: Biomarker protein detection likely failed due to the low (femtomoles/liter) predicted concentration of T. pallidum proteins. Alternative sample preparation strategies may improve the detectability of T. pallidum proteins in biofluids.

Symptom screening for active tuberculosis in pregnant women living with HIV

Editorial note This protocol will not progress to review stage as it no longer meets Cochrane's methodological standards. This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows: To assess the accuracy of the four-symptom screen (cough, fever, night sweats, or weight loss) for identifying active TB in pregnant PLHIV who are screened in an outpatient or community setting. To investigate potential sources of heterogeneity of the accuracy of the four-symptom screen between studies including: ART status, CD4 cell count, gestational age, pregnancy stage (pregnancy vs. postpartum), screening test definition of cough (any cough vs. cough greater than 2 weeks).To describe the accuracy of single symptoms included within the four-symptom screen, additioal symptoms or symptom combinations, for identifying active TB in pregnant PLHIV. For example, additional symptoms may include failure to gain weight or fatigue.

Detection of the tuberculosis antigenic marker mannose-capped lipoarabinomannan in pretreated serum by surface-enhanced Raman scattering

The ability to detect tuberculosis (TB) continues to be a global health care priority. This paper describes the development and preliminary assessment of the clinical accuracy of a heterogeneous immunoassay that integrates a serum pretreatment process with readout by surface-enhanced Raman scattering (SERS) for the low-level detection of mannose-capped lipoarabinomannan (ManLAM). ManLAM is a major virulence factor in the infectious pathology of Mycobacterium tuberculosis (Mtb) that has been found in the serum and other body fluids of infected patients. The effectiveness of ManLAM as a TB diagnostic marker, however, remains unproven for reasons not yet well understood. As reported herein, we have found that (1) ManLAM complexes with proteins and possibly other components in serum; (2) these complexes have a strongly detrimental impact on the ability to detect ManLAM using an immunoassay; (3) a simple pretreatment step can disrupt this complexation; and (4) disruption by pretreatment improves detection by 250×. We also describe the results from a preliminary assessment on the utility of serum pretreatment by running immunoassays on archived specimens from 24 TB-positive patients and 10 healthy controls. ManLAM was measurable in 21 of the 24 TB-positive specimens, but not in any of the 10 control specimens. These findings, albeit for a very small specimen set, translate to a clinical sensitivity of 87.5% and a clinical specificity of 100%. Together, these results both provide much needed evidence for the clinical utility of ManLAM as a TB marker, and demonstrate the potential utility of our overall approach to serve as a new strategy for the development of diagnostic tests for this disease.

Importance of specimen pretreatment for the low-level detection of mycobacterial lipoarabinomannan in human serum

Patient care and prevention of disease outbreaks rely heavily on the performance of diagnostic tests. These tests are typically carried out in serum, urine, and other complex sample matrices, but are often plagued by a number of matrix effects such as nonspecific adsorption and complexation with circulating proteins. This paper demonstrates the importance of sample pretreatment to overcome matrix effects, enabling the low-level detection of a disease marker for tuberculosis (TB). The impact of pretreatment is illustrated by detecting a cell wall component unique to mycobacteria, lipoarabinomannan (LAM). LAM is a major virulence factor in the infectious pathology of Mycobacterium tuberculosis (Mtb) and has been successfully detected in the body fluids of TB-infected individuals; however, its clinical sensitivity - identifying patients with active infection - remains problematic. This and the companion paper show that the detection of LAM in an immunoassay is plagued by its complexation with proteins and other components in serum. Herein, we present the procedures and results from an investigation of several different pretreatment schemes designed to disrupt complexation and thereby improve detection. These sample pretreatment studies, aimed at determining the optimal conditions for complex disruption, were carried out by using a LAM simulant derived from the nonpathogenic M. smegmatis, a mycobacterium often used as a model for Mtb. We have found that a perchloric acid-based pretreatment step improves the ability to detect this simulant by ∼1500× with respect to that in untreated serum. This paper describes the approach to pretreatment, how pretreatment improves the detection of the LAM simulant in human serum, and the results from a preliminary investigation to identify possible contributors to complexation by fractionating serum according to molecular weight. The companion paper applies this pretreatment approach to assays of TB patient samples.

Discovery of a unique Mycobacterium tuberculosis protein through proteomic analysis of urine from patients with active tuberculosis

Identification of pathogen-specific biomarkers present in patients' serum or urine samples can be a useful diagnostic approach. In efforts to discover Mycobacterium tuberculosis (Mtb) biomarkers we identified by mass spectroscopy a unique 21-mer Mtb peptide sequence (VVLGLTVPGGVELLPGVALPR) present in the urines of TB patients from Zimbabwe. This peptide has 100% sequence homology with the protein TBCG_03312 from the C strain of Mtb (a clinical isolate identified in New York, NY, USA) and 95% sequence homology with Mtb oxidoreductase (MRGA423_21210) from the clinical isolate MTB423 (identified in Kerala, India). Alignment of the genes coding for these proteins show an insertion point mutation relative to Rv3368c of the reference H37Rv strain, which generated a unique C-terminus with no sequence homology with any other described protein. Phylogenetic analysis utilizing public sequence data shows that the insertion mutation is apparently a rare event. However, sera from TB patients from distinct geographical areas of the world (Peru, Vietnam, and South Africa) contain antibodies that recognize a purified recombinant C-terminus of the protein, thus suggesting a wider distribution of isolates that produce this protein.

Stool Xpert MTB/RIF and urine lipoarabinomannan for the diagnosis of tuberculosis in hospitalized HIV-infected children

BACKGROUND

Tuberculosis (TB) causes substantial morbidity and mortality in HIV-infected children. Sample collection and the paucibacillary nature of TB in children makes diagnosis challenging. Rapid diagnostic tools using easily obtained specimens are urgently needed.

METHODS

Hospitalized, HIV-infected children aged 12 years or less enrolled in a randomized controlled trial (NCT02063880) comparing urgent to post-stabilization antiretroviral therapy initiation in Kenya underwent TB evaluation. At enrollment, sputum or gastric aspirates were collected for TB culture and Xpert, stool for Xpert, and urine for lipoarabinomannan (LAM). When possible, a second sputum/gastric aspirate for culture was obtained. Stool Xpert and urine LAM performance were compared to reference sputum/gastric aspirate culture.

RESULTS

Among 165 HIV-infected children, median age was 24 months [interquartile range (IQR) 13-58], median CD4% was 14.3 (IQR 8.9-22.0%), and 114 (69.5%) had severe immunosuppression. Thirteen (7.9%) children had confirmed TB (positive culture and/or Xpert). Sputum/gastric aspirate Xpert, stool Xpert, and urine LAM sensitivities were 60% [95% confidence interval (CI) 26-88%], 63% (95% CI 25-92%), and 43% (95% CI 10-82%), respectively. Specificity was 98% (95% CI 94-100%) for sputum/gastric aspirate Xpert, 99% (95% CI 95-100%) for stool Xpert, and 91% (95% CI 84-95%) for urine LAM. Stool Xpert and urine LAM sensitivity increased among children with severe immunosuppression [80% (95% CI 28-100) and 60% (95% Cl 15-95%)].

CONCLUSION

Stool Xpert had similar performance compared with sputum/gastric aspirate Xpert to detect TB. Urine LAM had lower sensitivity and specificity, but increased among children with severe immunosuppression. Stool Xpert and urine LAM can aid rapid detection of TB in HIV-infected children using easily accessible samples.

Empiric TB Treatment of Severely Ill Patients With HIV and Presumed Pulmonary TB Improves Survival

RATIONALE

In 2007, World Health Organization (WHO) issued emergency recommendations on empiric treatment of sputum acid-fast bacillus smear-negative patients with possible tuberculosis (TB) in HIV-prevalent areas, and called for operational research to evaluate their effectiveness. We sought to determine if early, empiric TB treatment of possible TB patients with abnormal chest radiography or severe illness as suggested by the 2007 WHO guidelines, is associated with improved survival.

METHODS

We prospectively enrolled consecutive HIV-seropositive inpatients at Mulago Hospital in Kampala, Uganda, from 2007 to 2011 with cough for ≥2 weeks. We retrospectively examined the effect of empiric TB treatment before discharge on 8-week survival among those with and without a WHO-defined "danger sign," including fever >39°C, tachycardia >120 beats per minute, or tachypnea >30 breaths per minute. We modeled the interaction between empiric TB treatment and danger signs, and their combined effect on 8-week survival, and adjusted for relevant covariates.

RESULTS

Among 631 sputum smear-negative patients, 322 (51%) had danger signs. Cumulative 8-week survival of patients with danger signs was significantly higher with empiric TB treatment (80%) than without treatment (64%, P < 0.001). After adjusting for duration of cough and concurrent hypoxemia, patients with danger signs who received empiric TB treatment had a 44% reduction in 8-week mortality (risk ratio 0.56, 95% confidence interval: 0.34-0.91, P = 0.020).

CONCLUSIONS

Empiric TB treatment of HIV-seropositive, smear-negative, presumed pulmonary TB patients with 1 or more danger signs is associated with improved 8-week survival. Enhanced implementation of the 2007 WHO empiric treatment recommendations should be encouraged whenever and wherever rapid and highly sensitive diagnostic tests for TB are unavailable.

Tuberculosis Diagnostics: State of the Art and Future Directions

Rapid and accurate diagnosis is critical for timely initiation of anti-tuberculosis (TB) treatment, but many people with TB (or TB symptoms) do not have access to adequate initial diagnosis. In many countries, TB diagnosis is still reliant on sputum microscopy, a test with known limitations. However, new diagnostics are starting to change the landscape. Stimulated, in part, by the success and rollout of Xpert MTB/RIF, an automated, molecular test, there is now considerable interest in new technologies. The landscape looks promising with a pipeline of new tools, particularly molecular diagnostics, and well over 50 companies actively engaged in product development, and many tests have been reviewed by WHO for policy endorsement. However, new diagnostics are yet to reach scale, and there needs to be greater convergence between diagnostics development and the development of shorter TB drug regimens. Another concern is the relative absence of non-sputum-based diagnostics in the pipeline for children, and of biomarker tests for triage, cure, and latent TB progression. Increased investments are necessary to support biomarker discovery, validation, and translation into clinical tools. While transformative tools are being developed, high-burden countries will need to improve the efficiency of their health care delivery systems, ensure better uptake of new technologies, and achieve greater linkages across the TB and HIV care continuum. While we wait for next-generation technologies, national TB programs must scale up the best diagnostics currently available, and use implementation science to get the maximum impact.

Clinic-Based Urinary Lipoarabinomannan as a Biomarker of Clinical Disease Severity and Mortality Among Antiretroviral Therapy-Naive Human Immunodeficiency Virus-Infected Adults in South Africa

Background

Urinary lipoarabinomannan (LAM) has limited sensitivity for diagnosing active human immunodeficiency virus (HIV)-associated tuberculosis (TB) disease, but LAM screening at HIV diagnosis might identify adults with more severe clinical disease or greater risk of mortality.

Methods

We enrolled antiretroviral therapy-naive HIV-infected adults from 4 clinics in Durban. Nurses performed urine LAM testing using a rapid assay (Determine TB LAM) graded from low (1+) to high (≥3+) intensity. Urine LAM results were not used to guide anti-TB therapy. We assessed TB-related symptoms and obtained sputum for mycobacterial smear and culture. Participants were observed for 12 months, and we used multivariable Cox proportional hazard models to determine hazard ratios for all-cause mortality.

Results

Among 726 HIV-infected adults with median CD4 of 205 cells/mm³ (interquartile range, 79–350 cells/mm³), 93 (13%) were LAM positive and 89 (12%) participants died during the follow-up period. In multivariable analyses, urine LAM-positive participants had a mortality hazard ratio (MHR) of 3.58 (95% confidence interval [CI], 2.20–5.81) for all-cause mortality. Among participants with mycobacterial-confirmed TB, urine LAM-positivity had a 2.91 (95% CI, 1.26–6.73) MHR for all participants and a 4.55 (95% CI, 1.71–12.1) MHR for participants with CD4 ≤100 cell/mm³. Participants with LAM-positive TB had significantly more clinical signs and symptoms of disease, compared with participants with LAM-negative TB disease.

Conclusions

Among HIV-infected adults, urinary LAM-positive patients had more clinical disease severity and a 3-fold increase in 12-month mortality compared with those who were LAM negative.

The clinical utility of the urine-based lateral flow lipoarabinomannan assay in HIV-infected adults in Myanmar: an observational study

BACKGROUND

The use of the point-of-care lateral flow lipoarabinomannan (LF-LAM) test may expedite tuberculosis (TB) diagnosis in HIV-positive patients. However, the test's clinical utility is poorly defined outside sub-Saharan Africa.

METHODS

The study enrolled consecutive HIV-positive adults at a tertiary referral hospital in Yangon, Myanmar. On enrolment, patients had a LF-LAM test performed according to the manufacturer's instructions. Clinicians managing the patients were unaware of the LF-LAM result, which was correlated with the patient's clinical course over the ensuing 6 months.

RESULTS

The study enrolled 54 inpatients and 463 outpatients between July 1 and December 31, 2015. On enrolment, the patients' median (interquartile range) CD4 T-cell count was 270 (128-443) cells/mm³. The baseline LF-LAM test was positive in 201/517 (39%). TB was confirmed microbiologically during follow-up in 54/517 (10%), with rifampicin resistance present in 8/54 (15%). In the study's resource-limited setting, extrapulmonary testing for TB was not possible, but after 6 months, 97/201 (48%) with a positive LF-LAM test on enrolment had neither died, required hospitalisation, received a TB diagnosis or received empirical anti-TB therapy, suggesting a high rate of false-positive results. Of the 97 false-positive tests, 89 (92%) were grade 1 positive, suggesting poor test specificity using this cut-off. Only 21/517 (4%) patients were inpatients with TB symptoms and a CD4 T-cell count of < 100 cells/mm³. Five (24%) of these 21 died, three of whom had a positive LF-LAM test on enrolment. However, all three received anti-TB therapy before death - two after diagnosis with Xpert MTB/RIF testing, while the other received empirical treatment. It is unlikely that knowledge of the baseline LF-LAM result would have averted any of the study's other 11 deaths; eight had a negative test, and of the three patients with a positive test, two received anti-TB therapy before death, while one died from laboratory-confirmed cryptococcal meningitis. The test was no better than a simple, clinical history excluding TB during follow-up (negative predictive value (95% confidence interval): 94% (91-97) vs. 94% (91-96)).

CONCLUSIONS

The LF-LAM test had limited clinical utility in the management of HIV-positive patients in this Asian referral hospital setting.

Diagnosis of Tuberculosis in HIV Co-infected Individuals: Current Status, Challenges and Opportunities for the Future

Tuberculosis (TB) remains one of the most important causes of death among people co-infected with human immunodeficiency virus (HIV). The diagnosis of TB remains challenging in HIV co-infected individuals, due to a high frequency of smear-negative disease and high rates of extrapulmonary TB. Accurate, ease of use and rapid diagnosis of active TB are critical to the World Health Organization (WHO) End TB Strategy by 2050. Traditional laboratory techniques do not provide rapid and accurate results to effectively manage HIV co-infected patients. Over the last decade, molecular methods have provided significant steps in the fight against TB. However, many HIV co-infected patients do not have access to these molecular diagnostic tests. Given the costs closely related with confirming a TB diagnosis in HIV patients, an overtreatment for TB is used in this patient population. Nowadays, an estimated US $8 billion a year is required to provide TB treatment, which is very high compared with making an important strategy to improve the current diagnostic tests. This review focuses on current advances in diagnosing active TB with an emphasis on the diagnosis of HIV-associated TB. Also discussed are the main challenges that need to be overcome for improving an adequate initial diagnosis of active TB in HIV-positive patients.

GeneXpert MTB/RIF assay in the diagnosis of urinary tuberculosis from urine specimens

Conventional bacteriological methods are not generally helpful in diagnosing urinary tuberculosis (UTB). GeneXpert is endorsed for the detection of pulmonary tuberculosis, whereas the data on its utility for urine specimens is limited. In this study, we aimed to evaluate its performance on urine specimens in a country with high TB incidence. A total of 163 suspected UTB patients were consecutively enrolled in the analysis, including 37 (22.7%) culture-positive and 44 (27.0%) clinically diagnosed UTB cases. Compared with conventional culture, the sensitivity of GeneXpert (94.6%) was significantly higher than that of smear microscopy (40.5%, P < 0.001). When setting clinical diagnosis as gold standard, 51 out of 81 clinically diagnosed UTB cases were detected by GeneXpert, demonstrating a sensitivity of 63.0%, which was significantly higher than that of smear microscopy (18.5%, P < 0.001) and culture (45.7%, P = 0.027), respectively. In addition, the proportion of UTB cases in the migrant population was significantly higher than that in the resident population (P = 0.019). To conclude, our data demonstrate that GeneXpert outperforms AFB smear and culture for the detection of MTB in urine samples, which provides an alternative for the diagnosis of UTB. The migrant population and previously diagnosed TB cases are high risk factors for developing UTB cases.

Detection of Lipid and Amphiphilic Biomarkers for Disease Diagnostics

Rapid diagnosis is crucial to effectively treating any disease. Biological markers, or biomarkers, have been widely used to diagnose a variety of infectious and non-infectious diseases. The detection of biomarkers in patient samples can also provide valuable information regarding progression and prognosis. Interestingly, many such biomarkers are composed of lipids, and are amphiphilic in biochemistry, which leads them to be often sequestered by host carriers. Such sequestration enhances the difficulty of developing sensitive and accurate sensors for these targets. Many of the physiologically relevant molecules involved in pathogenesis and disease are indeed amphiphilic. This chemical property is likely essential for their biological function, but also makes them challenging to detect and quantify in vitro. In order to understand pathogenesis and disease progression while developing effective diagnostics, it is important to account for the biochemistry of lipid and amphiphilic biomarkers when creating novel techniques for the quantitative measurement of these targets. Here, we review techniques and methods used to detect lipid and amphiphilic biomarkers associated with disease, as well as their feasibility for use as diagnostic targets, highlighting the significance of their biochemical properties in the design and execution of laboratory and diagnostic strategies. The biochemistry of biological molecules is clearly relevant to their physiological function, and calling out the need for consideration of this feature in their study, and use as vaccine, diagnostic and therapeutic targets is the overarching motivation for this review.

Analytical Tools to Improve Optimization Procedures for Lateral Flow Assays

Immunochromatographic or lateral flow assays (LFAs) are inexpensive, easy to use, point-of-care medical diagnostic tests that are found in arenas ranging from a doctor’s office in Manhattan to a rural medical clinic in low resource settings. The simplicity in the LFA itself belies the complex task of optimization required to make the test sensitive, rapid and easy to use. Currently, the manufacturers develop LFAs by empirical optimization of material components (e.g., analytical membranes, conjugate pads and sample pads), biological reagents (e.g., antibodies, blocking reagents and buffers) and the design of delivery geometry. In this paper, we will review conventional optimization and then focus on the latter and outline analytical tools, such as dynamic light scattering and optical biosensors, as well as methods, such as microfluidic flow design and mechanistic models. We are applying these tools to find non-obvious optima of lateral flow assays for improved sensitivity, specificity and manufacturing robustness.

Electrochemical determination of M. tuberculosis antigen based on Poly(3,4-ethylenedioxythiophene) and functionalized carbon nanotubes hybrid platform

An electrochemical DNA aptasensor for the detection of Mycobacterium tuberculosis (M. tb) antigen MPT64, was developed using Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). The biotinylated aptamer was immobilized onto streptavidin attached to -COOH functionalized CNTs via streptavidin-biotin interaction. Various characterization studies as FT-IR, FE-SEM, EIS and DPV were done to validate each fabrication step of the aptasensor. Optimization studies related to aptamer concentration and response time were performed. The electrochemical signal generated from the aptamer-target molecule interaction was monitored electrochemically by differential pulse voltammetry in the presence of [Fe(CN)₆]^3-/4- as a redox probe. The aptasensor exhibited limit of detection of 0.5±0.2fgmL^-1 within 15min with stability of 27 days at 4°C and reusability of 7 times after repeated regeneration with 50mM NaOH. The potential application of the aptasensor was established by spike-in studies to obtain recovery in between (88-95)%.

Utility of urine lipoarabinomannan (LAM) in diagnosing tuberculosis and predicting mortality with and without HIV: prospective TB cohort from the Thailand Big City TB Research Network

OBJECTIVES

To evaluate the applicability and accuracy of the urine lipoarabinomannan (LAM) test in tuberculosis (TB)/HIV co-infected patients and HIV-negative patients with disseminated TB.

METHODS

Frozen urine samples obtained at baseline from patients in the TB research cohort with proven culture-positive TB were selected for blinded urine LAM testing. One hundred and nine patients were categorized into four groups: (1) HIV-positive patients with TB; (2) HIV-negative patients with disseminated TB; (3) HIV-negative immunocompromised patients with TB; and (4) patients with diseases other than TB. The sensitivity of urine LAM testing for culture-positive TB, specificity of urine LAM testing for patients without TB, positive predictive value (PPV), and negative predictive value (NPV) were assessed.

RESULTS

The sensitivity of the urine LAM test in group 1 patients with a CD4 T-cell count of >100, ≤100, and ≤50 cells/mm³ was 38.5%, 40.6%, and 45%, respectively. The specificity and PPV of the urine LAM test were >80%. The sensitivity of the test was 20% in group 2 and 12.5% in group 3, and the specificity and PPV were 100% for both groups. A positive urine LAM test result was significantly associated with death.

CONCLUSIONS

This promising diagnostic tool could increase the yield of TB diagnosis and may predict the mortality rate of TB infection, particularly in TB/HIV co-infected patients.

Early detection of the growth of Mycobacterium tuberculosis using magnetophoretic immunoassay in liquid culture

Tuberculosis (TB) is an often neglected, epidemic disease that remains to be controlled by contemporary techniques of medicine and biotechnology. In this study, a nanoscale sensing system, referred to as magnetophoretic immunoassay (MPI) was designed to capture culture filtrate protein (CFP)-10 antigens effectively using two different types of nanoparticles (NPs). Two specific monoclonal antibodies against CFP-10 antigen were used, including gold NPs for signaling and magnetic particles for separation. These results were carefully compared with those obtained using the commercial mycobacteria growth indicator tube (MGIT) test via 2 sequential clinical tests (with ca. 260 clinical samples). The sensing linearity of MPI was shown in the range of pico- to micromoles and the detection limit was 0.3pM. MPI using clinical samples shows robust and reliable sensing while monitoring Mycobacterium tuberculosis (MTB) growth with monitoring time 3-10 days) comparable to that with the MGIT test. Furthermore, MPI distinguished false-positive samples from MGIT-positive samples, probably containing non-tuberculous mycobacteria. Thus, MPI shows promise in early TB diagnosis.

Diagnostic accuracy, incremental yield and prognostic value of Determine TB-LAM for routine diagnostic testing for tuberculosis in HIV-infected patients requiring acute hospital admission in South Africa: a prospective cohort

BACKGROUND

We previously reported that one-third of HIV-positive adults requiring medical admission to a South African district hospital had laboratory-confirmed tuberculosis (TB) and that almost two-thirds of cases could be rapidly diagnosed using Xpert MTB/RIF-testing of concentrated urine samples obtained on the first day of admission. Implementation of urine-based, routine, point-of-care TB screening is an attractive intervention that might be facilitated by use of a simple, low-cost diagnostic tool, such as the Determine TB-LAM lateral-flow rapid test for HIV-associated TB.

METHODS

Sputum, urine and blood samples were systematically obtained from unselected HIV-positive adults within 24 hours of admission to a South African township hospital. Additional clinical samples were obtained during hospitalization as clinically indicated. TB was defined by the detection of Mycobacterium tuberculosis in any sample using Xpert MTB/RIF or liquid culture. The diagnostic yield, accuracy and prognostic value of urine-lipoarabinomannan (LAM) testing were determined, but urine-LAM results did not inform treatment decisions.

RESULTS

Consecutive HIV-positive adult acute medical admissions not already receiving TB treatment (n = 427) were enrolled regardless of clinical presentation or symptoms. TB was diagnosed in 139 patients (TB prevalence 32.6%; median CD4 count 80 cells/μL). In the first 24 hours of admission, sputum (spot and/or induced) samples were obtained from 37.0% of patients and urine samples from 99.5% of patients (P < 0.001). The diagnostic yields from these specimens were 19.4% (n = 27/139) for sputum-microscopy, 26.6% (n = 37/139) for sputum-Xpert, 38.1% (n = 53/139) for urine-LAM and 52.5% (n = 73/139) for sputum-Xpert/urine-LAM combined (P < 0.01). Corresponding yields among patients with CD4 counts <100 cells/μL were 18.9%, 24.3%, 55.4% and 63.5%, respectively (P < 0.01). The diagnostic yield of urine-LAM was unrelated to respiratory symptoms, and LAM assay specificity (using a grade-2 cut-off) was 98.9% (274/277; 95% confidence interval [CI] 96.9-99.8). Among TB cases, positive urine-LAM status was strongly associated with mortality at 90 days (adjusted hazard ratio 4.20; 95% CI 1.50-11.75).

CONCLUSIONS

Routine testing for TB in newly admitted HIV-positive adults using Determine TB-LAM to test urine provides major incremental diagnostic yield with very high specificity when used in combination with sputum testing and has important utility among those without respiratory TB symptoms and/or unable to produce sputum. The assay also rapidly identifies individuals with a poor prognosis.

Expedient synthesis of the heneicosasaccharyl mannose capped arabinomannan of the Mycobacterium tuberculosis cellular envelope by glycosyl carbonate donors

The global incidence of tuberculosis is increasing at an alarming rate, and Mycobacterium tuberculosis (Mtb) is the causative agent for tuberculosis, a disease with high mortality. Lipoarabinomannan (LAM) is one of the major components of the Mtb cellular envelope and is an attractive scaffold for developing anti-tubercular drugs, vaccines and diagnostics. Herein, a highly convergent strategy is developed to synthesize heneicosasaccharyl arabinomannan for the first time. The arabinomannan synthesized in this endeavour has several 1,2-trans or α-Araf linkages and three 1,2-cis or β-Araf linkages end capped with 1,2-trans or α-Manp linkages. All the key glycosidations were performed with alkynyl carbonate glycosyl donors under [Au]/[Ag] catalysis conditions, which gave excellent yields and stereoselectivity even for the reactions between complex and branched oligosaccharides. The resultant allyl oligosaccharide was globally deprotected to obtain the heneicosasaccharyl arabinomannan as a propyl glycoside. In summary, heneicosasaccharyl mannose capped arabinomannan synthesis was achieved in 56 steps with 0.016% overall yield.