Glycolipids of Mycobacterium tuberculosis strain H37Rv are potential serological markers for diagnosis of active tuberculosis

A systematic review of potential screening biomarkers for active TB disease

INTRODUCTION

The standard TB Four Symptom Screen does not meet the World Health Organization (WHO) ideal screening criteria for having greater than 90% sensitivity to identify active TB disease, regardless of HIV status. To identify novel screening biomarkers for active TB, we performed a systematic review of any cohort or case-control study reporting associations between screening biomarkers and active TB disease.

METHODS

We searched PubMed and Embase for articles published before October 10, 2021. We included studies from high or medium tuberculosis burden countries. We excluded articles focusing on C-reactive protein and lipoarabinomannan. For all included biomarkers, we calculated sensitivity, specificity and 95% confidence intervals, and assessed study quality using a tool adapted from the QUADAS-2 risk of bias.

RESULTS

From 8,062 abstracts screened, we included 79 articles. The articles described 302 unique biomarkers, including host antibodies, host proteins, TB antigens, microRNAs, whole blood gene PCRs, and combinations of biomarkers. Of these, 23 biomarkers had sensitivity greater than 90% and specificity greater than 70%, meeting WHO criteria for an ideal screening test. Among the eleven biomarkers described in people living with HIV, only one had a sensitivity greater than 90% and specificity greater than 70% for active TB.

CONCLUSION

Further evaluation of biomarkers of active TB should be pursued to accelerate identification of TB disease.

An evaluation of liposome-based diagnostics of pulmonary and extrapulmonary tuberculosis

Introduction: Tuberculosis (TB) is still one of the major global health threats and delayed diagnosis or misdiagnosis continues to fuel the global epidemic. The conventional diagnostic approaches have shortcomings that might hinder the process of diagnosis of the disease and ultimately affect the prognosis.Area covered: We emphasize on the process of the synthesis of liposomes, its physicochemical properties affecting the formulation and their utilization in the field of molecular diagnostics for TB. The review also sheds a light on other nanoparticle-based molecular diagnostic approaches for TB. Despite the advent of science, we are yet to have a diagnostic tool that is simple, rapid, sensitive, and specific, and most importantly, one that enables us to demarcate patients with active tuberculosis from those with quiescent lesions, prior vaccination, or other diseases.Expert opinion: The utility of liposomes for diagnostic purposes has been attempted so as to overcome the challenges posed by conventional diagnostic tools for TB. Through this review, we present insights into liposome formulation and selection processes, various studies that report the use of liposome-based diagnostic tools for TB, as well as the limitations associated with the same that can be improvised to make the technology more efficient.

Tuberculosis Status and Coinfection of Pulmonary Fungal Infections in Patients Referred to Reference Laboratory of Health Centers Ghaemshahr City during 2007-2017

BACKGROUND

Pulmonary tuberculosis is one of the most important health concerns. Pulmonary fungal infections have clinical and radiological characteristics similar to tuberculosis which may be easily misdiagnosed as tuberculosis. This study aimed to evaluate tuberculosis (TB) status and coinfection of TB with pulmonary fungal infections in patients referred to reference laboratory of health centers Ghaemshahr city during 2007-2017.

METHODS

This cross-sectional study was conducted during eleven years, between 2007-2017, on 3577 patients with suspected TB referred to health centers of Ghaemshahr City. For isolation, sputum smear preparation and Ziehl-Neelson staining in companying with microscopy direct observation and KOH 10% + white Calcofluor staining was used. The culture of fungi was performed on Sabouraud Dextrose agar, Czapek and chrome agar media. Then, data were analyzed using SPSS software (version 16) through Student's t-test, Fisher test, and Odds Ratio. P values <0.05 were considered statistically significant.

RESULTS

Of 3577 patients, 10731 smears were prepared, 3.6% (n=130) of patients were identified as smear-positive pulmonary tuberculosis, 86.4% (n=3090) were smear negative and 10% (n=357) drug-resistant TB. The mean age of patients was 48±1.8 years. With increasing age, the prevalence of TB has increased which was statistically significant (P value <0.05). Prevalence of tuberculosis in the age group over than 57 years in males and females had an ascending trend. Amongst the positive tuberculosis patients, 16/130 cases (12.3%) had the coinfection of TB with fungi microorganisms.

CONCLUSION

Our findings showed the coinfection of fungi agents in patients with tuberculosis that should be considered.

Detection of Tuberculosis in HIV Co-infected Individuals: Use of Multiple ELISA Responses to 38kDa, Lipoarabinomannan and ESAT- 6 of M. tuberculosis

INTRODUCTION

There is a constant search for more sensitive and specific laboratory markers for tuberculosis (TB) infection. The early detection of TB in HIV co infected individuals is a diagnostic challenge. This is further compounded in those harbouring extrapulmonary disease.

AIM

To evaluate the use of multiple Enzyme Linked Immunosorbent Assays (ELISA) quantifying antibody responses to 38kDa, LAM and ESAT-6 M.tb antigens in detection of TB in patients with TB and HIV-TB co-infection.

MATERIALS AND METHODS

This is a cross-sectional study carried out in Hyderabad, India. Patient groups included 124 HIV-TB {62 with pulmonary TB (PTB) and 62 with extrapulmonary TB (ETB)}, 39 TB, 56 HIV and 57 healthy subjects (HS). A combination of anti 38kDa and LAM ELISAs measuring IgG, IgM and IgA levels and another ELISA measuring anti ESAT-6 combined antibody levels of IgG, IgM and IgA were evaluated. One-way ANOVA was performed to compare antibody responses among groups. To assess the efficacy of multiple ELISAs in detecting TB, concomitant seropositivity of an individual for all four ELISAs were evaluated for sensitivity and specificity.

RESULTS

A single ELISA carried out to detect TB in HIV patients showed a sensitivity ranging from 39% to 72%. The sensitivities of concomitant evaluation of multiple ELISAs were 92% for any single, 72% for any two, 44% for any three and 14% for any four. Based on the specificities, a simple algorithm for TB detection can be deduced. When four ELISAs are positive (specificity 100%) in a patient-confirmed TB; when three ELISAs are positive (specificity 98%) - probably TB; when two ELISAs are positive (specificity 95%) - possibly TB; and when one ELISA is positive (specificity 70%) - suspicion of TB.

CONCLUSION

The present study establishes the value of combining two or more M.tb antigen based ELISAs to enhance the sensitivity and specificity of TB detection in patients with tuberculosis as well as in those co-infected with HIV.

Fast and efficient detection of tuberculosis antigens using liposome encapsulated secretory proteins of Mycobacterium tuberculosis

PURPOSE

A rapid and efficient diagnostic test was developed for the detection of Mycobacterium tuberculosis antigens in serum samples of active tuberculosis (TB) and extrapulmonary TB patients via a liposomal agglutination-based method.

METHODS

A rapid card test has been developed to facilitate the recognition of high-affinity binding rabbit raised purified culture filtrate protein antibodies coupled on the surface of activated liposomal preparation. In the presence of TB antigens, the polyclonal antibodies bound to the liposomal particles demonstrate a visible agglutination reaction.

RESULTS

The developed assay was simple, rapid, reliable, sensitive, and specific as a diagnostic test for the detection of antigens in serum samples of clinically confirmed cases of TB within 4-5 minutes' duration. The test was evaluated at different hospitals, medical colleges, and pathology centers, and involved 1483 participants. This investigation was conducted to detect the presence of these antigens during the period of active growth of the microorganism in serum samples for pulmonary TB and processed tissue biopsy for other extrapulmonary TB. Results obtained using this test were compared with acid-fast bacilli smear and culture results.

CONCLUSION

Our study demonstrated that the newly developed liposome tuberculosis antigen card test detected antigens in our study population with approximately 97.48% sensitivity and 95.79% specificity. This is the first study to report the liposomal encapsulation of culture filtrate proteins from M. tuberculosis for diagnostic application.

Evaluation of Mycobacterium tuberculosis--specific antibody responses in populations with different levels of exposure from Tanzania, Ethiopia, Brazil, and Denmark

BACKGROUND

New, simple, and better-performing diagnostic tools are needed for the diagnosis of tuberculosis (TB). Much effort has been invested in developing an antibody-based test for TB, but to date, no such test has performed with sufficient sensitivity and specificity. A key question remaining is the extent to which the disappointing performance of current tests is associated with a high background prevalence of latent TB.

METHODS

We compared Mycobacterium tuberculosis-specific ESAT-6 and CFP-10 antibody responses in a total of 565 human serum samples from M. tuberculosis-uninfected donors and donors with latent infection, as well as samples from patients with active TB. Our study included samples from 4 countries, representing environments with low, intermediate, and high TB incidences.

RESULTS

We demonstrated significant increases in antibody levels in latently infected contacts, compared with M. tuberculosis-uninfected individuals, and in patients with active TB disease, compared with latently infected contacts. Furthermore, we found a striking increase in the magnitude of the antibody responses in samples obtained from infected Ethiopian individuals (with and without disease), compared with Danish and Brazilian infected individuals; this was presumably the result of higher exposure levels.

CONCLUSIONS

Our study confirms the presence of ESAT-6 and CFP-10 antibodies in patients with TB, and we demonstrate that significant antibody responses are not restricted to active TB disease but can reflect latent infection, particularly in areas with high levels of exposure to M. tuberculosis. This finding is important for the understanding of the poor discriminatory power of current serodiagnostic tests in regions of endemicity, and it may have major implications on the future development of serologic tests.

Modern approaches to a rapid diagnosis of tuberculosis: promises and challenges ahead

The limitations of the conventional methods for diagnosing tuberculosis have spurred multi-faceted research activities in this field throughout the world. Chromatographic methods appear promising but may not be widely available in the developing countries. Immuno-diagnostic methods using combinations ("cocktails") of antigens have high sensitivity and specificity and can easily be applied in the peripheral laboratories and in the field settings. Though expensive, molecular methods for diagnosis of tuberculosis have advantages of speed, sensitivity, and specificity. Adequate training of the eligible personnels in molecular methods and prevention of laboratory-dependent contamination may help reduce false positive results. Although, there are no clear guidelines, so far on how to make out the best from the gene amplification methods, yet their use may be encouraged with adequate quality controls, because of the inherent ingenuity and promises of these methods. Phage-based molecular methods provide rapid results in susceptibility tests for anti-tubercular drugs. In future, many sophisticated techniques are expected to hit the market for a rapid diagnosis of tuberculosis. In the developing countries, it is necessary to evaluate availability of suitable infrastructure and trained personnels before adopting modern diagnostic methods.