Evidence-based tuberculosis diagnosis

Tuberculosis Meningitis in People Living with HIV/AIDS in a Health Center in the Brazilian Amazon: A Silent Disease

Introduction

Tuberculosis (TB) is one of the ten leading causes of death worldwide and the leading cause of infection in people living with the human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) (PLWHA). It is a major public health problem in Brazil and worldwide.

Methods

This was a case series study of five meningeal tuberculosis and PLWHA coinfection patients admitted between June 2019 and June 2020, in a public hospital in the northern region of Brazil. Associated with clinical cases, we propose a discussion of the different laboratory diagnostic methods available in Brazil, with the aim of increasing the diagnosis of this very serious disease, with high mortality.

Results

The diagnosis of tuberculous meningitis is a challenge in clinical practice; thus, the clinical cases presented help the physician to recognize the signs and symptoms of the disease and improve the confirmatory diagnosis through acid-alcoholic resistant bacilli techniques, molecular testing, and mycobacteria culture in the cerebrospinal fluid.

Conclusion

Knowing the diagnostic methods of tuberculous meningitis and its characteristics is of paramount importance to increase the correct diagnosis and reduce mortality in delayed treatment.

Mycobacterium tuberculosis thymidylate kinase antigen assays for designating incipient, high-risk latent M.tb infection

BACKGROUND

Precise designation of high risk forms of latent Mycobacterium tuberculosis-M.tb infections (LTBI) is impossible. Delineation of high-risk LTBI can, however, allow for chemoprophylaxis and curtail majority cases of active tuberculosis (ATB). There is epidemiological evidence to support the view that LTBI in context of HIV-1 co-infection is high-risk for progression to ATB relative to LTBI among HIV-ve persons. We recently showed that assays of M.tb thymidylate kinase (TMKmt) antigen and host specific IgG can differentiate ATB from LTBI and or no TB (NTB, or healthy controls). In this study, we aimed to expose the differential levels of TMKmt Ag among HIV+ve co-infected LTBI relative to HIV-ve LTBI as a strategy to advance these assays for designating incipient LTBI.

METHODS

TMKmt host specific IgM and IgG detection Enzyme Immuno-Assays (EIA) were conducted on 40 TB exposed house-hold contacts (22 LTBI vs. 18 no TB (NTB) by QunatiFERON-TB GOLD®); and TMKmt Ag detection EIA done on 82 LTBI (46 HIV+ve vs 36 HIV-ve) and 9 NTB (American donors). Purified recombinant TMKmt protein was used as positive control for the Ag assays.

RESULTS

IgM levels were found to be equally low across QuantiFERON-TB GOLD® prequalified NTB and TB exposed house-hold contacts. Higher TMKmt host specific IgG trends were found among TB house-hold contacts relative to NTB controls. TMKmt Ag levels among HIV+ve LTBI were 0.2676 ± 0.0197 (95% CI: 0.2279 to 0.3073) relative to 0.1069 ± 0.01628 (95% CI: 0.07385 to 0.14) for HIV-ve LTBI (supporting incipient nature of LTBI in context of HIV-1 co-infection). NTB had TMKmt Ag levels of 0.1013 ± 0.02505 (5% CI: 0.0421 to 0.1606) (intimating that some were indeed LTBI).

CONCLUSIONS

TMKmt Ag levels represent a novel surrogate biomarker for high-risk LTBI, while host-specific IgG can be used to designate NTB from LTBI.

Sero-diagnosis of Active Mycobacterium tuberculosis Disease among HIV Co-infected Persons using Thymidylate Kinase based Antigen and Antibody Capture Enzyme Immuno-Assays

BACKGROUND

Clinical and laboratory diagnosis of Active Tuberculosis (ATB) and latent Mycobacterium Tuberculosis (M. tuberculosis) infections (LTBI) among people living with HIV/AIDS (PLWHA) presents formidable challenges. In the past, WHO issued an advisory against the use of existing TB sero-diagnostics. Emerging evidence, however, points to a precision of TB sero-diagnostics based on secretory rather than structural M. tuberculosis antigens. We hypothesized that secretory levels of M. tuberculosis thymidylate kinase (TMKmt) can Designate ATBI from LTBI and no TB (NTB). Here, we report in-house validation studies of levels of TMKmt antigen (Ag) and host specific TMKmt antibody (Ab) amongst HIV +ve and HIV -ve participants.

METHODS AND RESULTS

Direct TMKmt Ag and host specific IgG Ab detection EIAs were conducted on broadly consented, stored serum (N=281[Ag] vs. 214 [Ab] respective) samples stratified as either HIV +ve or HIV-ve ATB relative to LTBI and No TB. On one hand, UG-peptide 1 and its PAb-based EIAs accurately diagnosed ATB relative to LTBI and NTB among HIV +ve subjects {irrespectively: (a) Ag detection ATB=OD>0.490; 95% CI: 0.7446 to 0.8715 vs. LTBI=OD<0.490; 95% CI 0.4325 to 0.4829 vs. NTB=OD<0.26; 95% CI 0.1675 to 0.2567 and (b) TMKmt specific IgG detection ATB=OD>1.00; 95% CI 1.170 to 1.528 [HIV +ve] and 2.044 to 2.978 [HIV -ve] respectively vs. LTBI=OD<1.00; 95% CI 0.2690 to 0.6396 vs. NTB=OD<; 95% CI 0.1527 to 0.8751}. HIV -ve ATB presented with Ag levels greater than NTB and less than LTBI (i.e. ATB -ve=<0.490 ODs>0.26), but displayed better ant-TMKmt IgG responses (OD>2.00; 95% CI 2.044 to 2.978) relative to HIV +ve ATB (OD<1.600; 95% CI 1.170 to 1.528); suggesting a better control of M. tuberculosis-septicemia. On the other hand, UG-peptide 2 and its PAb-based EIAs did not demonstrate ATB diagnostic potential regardless of HIV sero-status, except towards designating NTB.

CONCLUSIONS

TMKmt Ab and Ag detecting EIAs based on UG-peptide 1 and its derivative PAb can accurately demarcate ATB from LTBI and NTB among HIV +ve subjects.

The accuracy of Aziza’s scoring system in limited slice non-enhanced thoracic CT for the diagnosis of adult pulmonary tuberculosis

Background: Tuberculosis (TB) is still a major cause of morbidity and mortality in Indonesia. Thus, a fast and accurate method in diagnosing pulmonary TB (PTB) is needed, especially in adult smear-negative-TB cases. The purpose of this study was to determine the accuracy of a novel scoring system (Aziza’s score) using clinical data and characteristic abnormalities that are found in the limited slice non-enhanced thoracic CT.Methods: This was a prospective cross-sectional study. A limited slice non-enhanced thoracic CT was performed to establish a diagnosis of PTB in patients with suspected PTB and to assess the diagnostic value of the scoring system. A reference standard used in this study was the clinical expertise of two pulmonologists. The scoring system was analyzed using bivariate and multivariate Cox regression analysis.Results: 84 of 130 suspected PTB patients were diagnosed as PTB. They were diagnosed based on pulmonary characteristic abnormalities that were found in the limited slice non-enhanced thoracic CT. The scoring system was analyzed using bivariate and multivariate Cox regression analysis. The total scores which were equal to or more than 29 could diagnose PTB with the accuracy of 96.1% (95% CIs=91.3–98.3), sensitivity of 96.5% (95% CIs=90.1–98.8), and specificity of 95.6% (95% CIs=90.1–98.8), This novel scoring method was name as an Aziza’s scoring system.Conclusion: Aziza’s scoring system performed in the limited slice non-enhanced thoracic CT has a higher accuracy compared to the reference standard for the diagnosis of adult PTB.

Accurate and effective multidrug-resistant Mycobacterium tuberculosis detection method using gap-filling ligation coupled with high-resolution capillary electrophoresis-based single strand conformation polymorphism

Tuberculosis (TB) has severely threatened public health via emerging multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis (MTB) strains. For effective TB treatment, rapid, accurate, and multiplex detection of drug resistance is extremely important. However, conventional methods for TB diagnosis are time consuming and have a limited effect on treatment. Nucleic acid-based molecular detection methods have been developed as an effective MDR/XDR-TB diagnosis technology. Among the nucleic acid-based methods, ligation-dependent methods are attractive as MDR/XDR-MTB detection technologies, but multiplex analysis is limited by the detection method. Although an electrophoresis-based method is considered for multiple target detection because it is free from the errors pertaining to hybridization-based systems, the procedure of multiplex analysis is quite complicated owing to the DNA size-based separation system. In this study, we report an accurate, rapid, and simple multiple MDR/XDR-MTB detection technology using gap-filling ligation reaction coupled with high-resolution capillary electrophoresis-based single-strand conformation polymorphism. Using this system, rapid and accurate MDR/XDR-MTB detection is feasible via similar length probes without the complicated step of probe design. We found that this method could accurately and effectively detect highly polymorphic regions in specific codons associated with drug resistance.

Evaluation of Giant African Pouched Rats for Detection of Pulmonary Tuberculosis in Patients from a High-Endemic Setting

Background

This study established evidence about the diagnostic performance of trained giant African pouched rats for detecting Mycobacterium tuberculosis in sputum of well-characterised patients with presumptive tuberculosis (TB) in a high-burden setting.

Methods

The TB detection rats were evaluated using sputum samples of patients with presumptive TB enrolled in two prospective cohort studies in Bagamoyo, Tanzania. The patients were characterised by sputum smear microscopy and culture, including subsequent antigen or molecular confirmation of Mycobacterium tuberculosis, and by clinical data at enrolment and for at least 5-months of follow-up to determine the reference standard. Seven trained giant African pouched rats were used for the detection of TB in the sputum samples after shipment to the APOPO project in Morogoro, Tanzania.

Results

Of 469 eligible patients, 109 (23.2%) were culture-positive for Mycobacterium tuberculosis and 128 (27.3%) were non-TB controls with sustained recovery after 5 months without anti-TB treatment. The HIV prevalence was 46%. The area under the receiver operating characteristic curve of the seven rats for the detection of culture-positive pulmonary tuberculosis was 0.72 (95% CI 0.66–0.78). An optimal threshold could be defined at ≥2 indications by rats in either sample with a corresponding sensitivity of 56.9% (95% CI 47.0–66.3), specificity of 80.5% (95% CI 72.5–86.9), positive and negative predictive value of 71.3% (95% CI 60.6–80.5) and 68.7% (95% CI 60.6–76.0), and an accuracy for TB diagnosis of 69.6%. The diagnostic performance was negatively influenced by low burden of bacilli, and independent of the HIV status.

Conclusion

Giant African pouched rats have potential for detection of tuberculosis in sputum samples. However, the diagnostic performance characteristics of TB detection rats do not currently meet the requirements for high-priority, rapid sputum-based TB diagnostics as defined by the World Health Organization.

A differential fluorescent receptor for nucleic acid analysis

Differential receptors use an array of sensors to recognize analytes. Each sensor in the array can recognize not one, but several analytes with different rates, so a single analyte triggers a response of several sensors in the array. The receptor thus produces a pattern of signals that is unique for each analyte, thereby enabling identification of a specific analyte by producing a "fingerprint" pattern. We applied this approach for the analysis of DNA sequences of Mycobacterium tuberculosis strains that differ by single nucleotide substitutions in the 81-bp hot-spot region that imparts rifampin resistance. The technology takes advantage of the new multicomponent, selfassembling sensor, which produces a fluorescent signal in the presence of specific DNA sequences. A differential fluorescent receptor (DFR) contained an array of three such sensors and differentiated at least eight DNA sequences. The approach requires only one molecular-beacon-like fluorescent reporter, which can be used by all three sensors. The DFR developed in this study represents a cost-efficient alternative to molecular diagnostic technologies that use fluorescent hybridization probes.

Tuberculosis management practices by private practitioners in Andhra Pradesh, India

Setting

Private medical practitioners in Visakhapatnam district, Andhra Pradesh, India.

Objectives

To evaluate self-reported TB diagnostic and treatment practices amongst private medical practitioners against benchmark practices articulated in the International Standards of Tuberculosis Care (ISTC), and factors associated with compliance with ISTC.

Design

Cross- sectional survey using semi-structured interviews.

Results

Of 296 randomly selected private practitioners, 201 (68%) were assessed for compliance to ISTC diagnostic and treatment standards in TB management. Only 11 (6%) followed a combination of 6 diagnostic standards together and only 1 followed a combination of all seven treatment standards together. There were 28 (14%) private practitioners who complied with a combination of three core ISTC (cough for tuberculosis suspects, sputum smear examination and use of standardized treatment). Higher ISTC compliance was associated with caring for more than 20 TB patients annually, prior sensitization to TB control guidelines, and practice of alternate systems of medicine.

Conclusion

Few private practitioners in Visakhapatnam, India reported TB diagnostic and treatment practices that met ISTC. Better engagement of the private sector is urgently required to improve TB management practices and to prevent diagnostic delay and drug resistance.

Human immunodeficiency virus-associated tuberculosis: update on prevention and treatment

Tuberculosis (TB) is the leading cause of opportunistic infection and mortality among HIV-infected persons. Screening for symptoms of TB in people with HIV infection, use of isoniazid preventive therapy for those with latent TB infection, earlier diagnosis and treatment of active TB disease, and early initiation of antiretroviral therapy are essential for controlling the spread of TB. Treatment of HIV-related TB is complicated by overlapping drug toxicities and drug-drug interactions between antiretroviral therapy and anti-TB therapy and risk for development of immune reconstitution inflammatory disease. This review provides an overview of the prevention and treatment of TB in HIV-infected persons.

Tuberculosis detection by giant african pouched rats

In recent years, operant discrimination training procedures have been used to teach giant African pouched rats to detect tuberculosis (TB) in human sputum samples. This article summarizes how the rats are trained and used operationally, as well as their performance in studies published to date. Available data suggest that pouched rats, which can evaluate many samples quickly, are sufficiently accurate in detecting TB to merit further investigation as a diagnostic tool.

Research questions and priorities for tuberculosis: a survey of published systematic reviews and meta-analyses

BACKGROUND

Systematic reviews are increasingly informing policies in tuberculosis (TB) care and control. They may also be a source of questions for future research. As part of the process of developing the International Roadmap for TB Research, we did a systematic review of published systematic reviews on TB, to identify research priorities that are most frequently suggested in reviews.

METHODOLOGY/PRINCIPAL FINDINGS

We searched EMBASE, MEDLINE, Web of Science, and the Cochrane Library for systematic reviews and meta-analyses on any aspect of TB published between 2005 and 2010. One reviewer extracted data and a second reviewer independently extracted data from a random subset of included studies. In total, 137 systematic reviews, with 141 research questions, were included in this review. We used the UK Health Research Classification System (HRCS) to help us classify the research questions and priorities. The three most common research topics were in the area of detection, screening and diagnosis of TB (32.6%), development and evaluation of treatments and therapeutic interventions (23.4%), and TB aetiology and risk factors (19.9%). The research priorities determined were mainly focused on the discovery and evaluation of bacteriological TB tests and drug-resistant TB tests and immunological tests. Other important topics of future research were genetic susceptibility linked to TB and disease determinants attributed to HIV/TB. Evaluation of drug treatments for TB, drug-resistant TB and HIV/TB were also frequently proposed research topics.

CONCLUSIONS

Systematic reviews are a good source of key research priorities. Findings from our survey have informed the development of the International Roadmap for TB Research by the TB Research Movement.

Opportunities for improved serodiagnosis of human tuberculosis, bovine tuberculosis, and paratuberculosis

Mycobacterial infections—tuberculosis (TB), bovine tuberculosis (bTB), and Johne's disease (JD)—are major infectious diseases of both human and animals. Methods presently in use for diagnosis of mycobacterial infections include bacterial culture, nucleic acid amplification, tuberculin skin test, interferon-γ assay, and serology. Serological tests have several advantages over other methods, including short turn-around time, relatively simple procedures, and low cost. However, current serodiagnostic methods for TB, bTB and JD exhibit low sensitivity and/or specificity. Recent studies that have aimed to develop improved serodiagnostic tests have mostly focused on identifying useful species-specific protein antigens. A review of recent attempts to improve diagnostic test performance indicates that the use of multiple antigens can improve the accuracy of serodiagnosis of these mycobacterial diseases. Mycobacteria also produce a variety of species-specific nonprotein molecules; however, only a few such molecules (e.g., cord factor and lipoarabinomannan) have so far been evaluated for their effectiveness as diagnostic antigens. For TB and bTB, there has been recent progress in developing laboratory-free diagnostic methods. New technologies such as microfluidics and “Lab-on-Chip” are examples of promising new technologies that can underpin development of laboratory-free diagnostic devices for these mycobacterial infections.

Bayesian meta-analysis of the accuracy of a test for tuberculous pleuritis in the absence of a gold standard reference

Absence of a perfect reference test is an acknowledged source of bias in diagnostic studies. In the case of tuberculous pleuritis, standard reference tests such as smear microscopy, culture and biopsy have poor sensitivity. Yet meta-analyses of new tests for this disease have always assumed the reference standard is perfect, leading to biased estimates of the new test's accuracy. We describe a method for joint meta-analysis of sensitivity and specificity of the diagnostic test under evaluation, while considering the imperfect nature of the reference standard. We use a Bayesian hierarchical model that takes into account within- and between-study variability. We show how to obtain pooled estimates of sensitivity and specificity, and how to plot a hierarchical summary receiver operating characteristic curve. We describe extensions of the model to situations where multiple reference tests are used, and where index and reference tests are conditionally dependent. The performance of the model is evaluated using simulations and illustrated using data from a meta-analysis of nucleic acid amplification tests (NAATs) for tuberculous pleuritis. The estimate of NAAT specificity was higher and the sensitivity lower compared to a model that assumed that the reference test was perfect.

Clinical research and development of tuberculosis diagnostics: moving from silos to synergy

The development, evaluation, and implementation of new and improved diagnostics have been identified as critical needs by human immunodeficiency virus (HIV) and tuberculosis researchers and clinicians alike. These needs exist in international and domestic settings and in adult and pediatric populations. Experts in tuberculosis and HIV care, researchers, healthcare providers, public health experts, and industry representatives, as well as representatives of pertinent US federal agencies (Centers for Disease Control and Prevention, Food and Drug Administration, National Institutes of Health, United States Agency for International Development) assembled at a workshop proposed by the Diagnostics Working Group of the Federal Tuberculosis Taskforce to review the state of tuberculosis diagnostics development in adult and pediatric populations.

Which new diagnostics for tuberculosis, and when?

Recently, new diagnostic tools for tuberculosis detection and resistance testing have become available. The World Health Organization endorses new tuberculosis diagnostics by using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) process. This endorsement process takes place when limited evidence beyond test accuracy is available. There is a need to provide guidance to tuberculosis programs about which new diagnostics to scale up and how best to position them in diagnostic algorithms. To speed adoption of new diagnostics for tuberculosis, the policy recommendation process should be revised to consist of 2 steps: technical recommendation and programmatic recommendation. Technical recommendation would follow the GRADE process and be based on accuracy with limited cost and feasibility data, while programmatic recommendation would include patient-important outcomes, cost-effectiveness when implemented under routine conditions, and factors critical to successful scale-up. The evidence for both steps should be systematically collected, but each requires different study designs.

European union standards for tuberculosis care

The European Centre for Disease Prevention and Control (ECDC) and the European Respiratory Society (ERS) jointly developed European Union Standards for Tuberculosis Care (ESTC) aimed at providing European Union (EU)-tailored standards for the diagnosis, treatment and prevention of tuberculosis (TB). The International Standards for TB Care (ISTC) were developed in the global context and are not always adapted to the EU setting and practices. The majority of EU countries have the resources and capacity to implement higher standards to further secure quality TB diagnosis, treatment and prevention. On this basis, the ESTC were developed as standards specifically tailored to the EU setting. A panel of 30 international experts, led by a writing group and the ERS and ECDC, identified and developed the 21 ESTC in the areas of diagnosis, treatment, HIV and comorbid conditions, and public health and prevention. The ISTCs formed the basis for the 21 standards, upon which additional EU adaptations and supplements were developed. These patient-centred standards are targeted to clinicians and public health workers, providing an easy-to-use resource, guiding through all required activities to ensure optimal diagnosis, treatment and prevention of TB. These will support EU health programmes to identify and develop optimal procedures for TB care, control and elimination.

Targeted detection of 65 kDa heat shock protein gene in endometrial biopsies for reliable diagnosis of genital tuberculosis

OBJECTIVE

To evaluate the clinical utility of PCR compared with other available diagnostic modalities in prompt diagnosis of female genital tuberculosis causing infertility.

STUDY DESIGN

Prospective case-controlled trial. Premenstrual endometrial biopsy specimens were collected from 150 infertile women of reproductive age group suspected of having genital tuberculosis. All patients underwent diagnostic endoscopy (laparoscopy and hysteroscopy) and the samples obtained were subjected to microscopy, culture by the BACTEC 460 TB System, histopathology and polymerase chain reaction (PCR) for detection of 165 bp region of 65 kDa gene of Mycobacterium tuberculosis. The results were correlated with the laparoscopic findings.

RESULTS

While the laparoscopy/hysteroscopy findings were indicative of tuberculosis in 12.6% of cases, 14.6% of the specimens showed evidence of 65 kDa gene of M. tuberculosis and only 3.33%, 1.33% and 0.66% were positive by culture, smear and histopathology, respectively.

CONCLUSION

Since laparoscopy, hysteroscopy other endoscopic procedures are associated with operative risks and may cause flaring of infection, and other conventional laboratory tests including histopathology have poor sensitivity, PCR-based detection of 65 kDa gene of M. tuberculosis in endometrial biopsy specimens could be a promising molecular diagnostic technique compared to conventional methods of diagnosis.

Diagnosis of tuberculosis: the experience at a specialized diagnostic laboratory

This work describes the experience at a tuberculosis clinical laboratory where relatively new TB diagnosis technologies; nucleic acid detection of two target strands, IS6110 and devR, by PCR and microscopic observation drug susceptibility (MODS) were used. The LJ culture was the gold standard. This evaluation was done from August 2007 to July 2009 on 463 sputum samples of tuberculosis suspects at a specialized tuberculosis clinic in Delhi, India.None of the tests we evaluated can accurately detect the presence or absence of Mycobacterium tuberculosis in all the samples and smear microscopy was found to be the most reliable assay in this study.The PCR assay could detect down to 2 pg of H37Rv DNA. Sensitivity, specificity was 0.40, 0.60 and 0.19, 0.81 for smear positive (n = 228) and negative samples (n = 235) respectively. In the MODS assay, sensitivity, specificity of 0.48, 0.52 and 0.38, 0.76 was observed for smear positive and negative samples. Sputum smear microscopy had sensitivity of 0.77 and specificity of 0.70.

Alternative methods of diagnosing drug resistance--what can they do for me?

During the last decade considerable attention has been focussed upon the development of new technologies and methodologies for detection of drug resistance in Mycobacterium tuberculosis. There is a growing acknowledgement that the redundancy in testing a full panel of first-line drugs is an unaffordable indulgence; since only resistance at baseline to either (or both) of the two most potent agents, isoniazid (H) and rifampicin (R), would usually prompt therapeutic modification there is a shift towards initial RH (or R alone for selected genotypic technologies) drug susceptibility testing (DST) followed, if necessary by further extended first and second line agent (currently phenotypic) DST. Most of the new drug susceptibility tests endorsed by the World Health Organization since 2007 deliver rapid RH (or R alone for selected genotypic technologies) DST. Targeting of patient groups with risk factors for drug resistance increases the proportion of tests that identify drug resistance, but in many settings at least as many patients with drug resistant disease will have no identifiable risk factors--equity of care demands that universal RH DST at baseline should be the goal. We review the bewildering array of choices facing TB program directors and attempt to provide objective information to help in deciding what tools may be best suited to different environments.

Atypical tuberculous pleural effusions

Typically, a tuberculous pleural effusion is submassive, unilateral, and has the appearance of a clear straw coloured fluid with a cellular content predominantly consisting of lymphocytes. Atypical characteristics of tuberculous pleural effusion do, however, need to be recognised to mitigate the risk of delayed diagnosis, the latter sometimes resulting in potentially avoidable deaths, and also to reduce the risk that untreated patients might transmit the disease.

Serological testing versus other strategies for diagnosis of active tuberculosis in India: a cost-effectiveness analysis

BACKGROUND

Undiagnosed and misdiagnosed tuberculosis (TB) drives the epidemic in India. Serological (antibody detection) TB tests are not recommended by any agency, but widely used in many countries, including the Indian private sector. The cost and impact of using serology compared with other diagnostic techniques is unknown.

METHODS AND FINDINGS

Taking a patient cohort conservatively equal to the annual number of serological tests done in India (1.5 million adults suspected of having active TB), we used decision analysis to estimate costs and effectiveness of sputum smear microscopy (US$3.62 for two smears), microscopy plus automated liquid culture (mycobacterium growth indicator tube [MGIT], US$20/test), and serological testing (anda-tb ELISA, US$20/test). Data on test accuracy and costs were obtained from published literature. We adopted the perspective of the Indian TB control sector and an analysis frame of 1 year. Our primary outcome was the incremental cost per disability-adjusted life year (DALY) averted. We performed one-way sensitivity analysis on all model parameters, with multiway sensitivity analysis on variables to which the model was most sensitive. If used instead of sputum microscopy, serology generated an estimated 14,000 more TB diagnoses, but also 121,000 more false-positive diagnoses, 102,000 fewer DALYs averted, and 32,000 more secondary TB cases than microscopy, at approximately four times the incremental cost (US$47.5 million versus US$11.9 million). When added to high-quality sputum smears, MGIT culture was estimated to avert 130,000 incremental DALYs at an incremental cost of US$213 per DALY averted. Serology was dominated by (i.e., more costly and less effective than) MGIT culture and remained less economically favorable than sputum smear or TB culture in one-way and multiway sensitivity analyses.

CONCLUSIONS

In India, sputum smear microscopy remains the most cost-effective diagnostic test available for active TB; efforts to increase access to quality-assured microscopy should take priority. In areas where high-quality microscopy exists and resources are sufficient, MGIT culture is more cost-effective than serology as an additional diagnostic test for TB. These data informed a recently published World Health Organization policy statement against serological tests.

Mechanisms of drug resistance in Mycobacterium tuberculosis and current status of rapid molecular diagnostic testing

Drug-resistant tuberculosis has become a global problem and a major public health concern. While mechanisms of resistance are fairly well characterized for most agents, particularly the first line agents, our knowledge of drug resistance is by no means exhaustive, and strains continue to emerge that carry novel resistance-related mutations. The purpose of this review is to summarize our current understanding of the genetic basis of drug resistance in Mycobacterium tuberculosis, highlighting emerging areas of research. The development of rapid detection methods has been a major breakthrough in the fight against drug-resistant tuberculosis. Rapid detection methods are available for both rifampin- and isoniazid-resistant tuberculosis, but have yet to be developed for other first line agents. Rapid detection methods will become increasingly important as multi-drug resistant strains of M. tuberculosis become more prevalent, even for detecting tuberculosis that is resistant to second line agents.

Xpert MTB/RIF: a new pillar in diagnosis of extrapulmonary tuberculosis?

Approximately 10 to 15% of tuberculosis (TB) cases in India are estimated to have extrapulmonary disease, and due to a lack of diagnostic means, they often remain untreated. The early detection of Mycobacterium tuberculosis and multidrug resistance is a priority in TB diagnosis to improve the successful treatment rate of TB and reduce transmission. The Xpert MTB/RIF (Xpert) test, recently endorsed by the World Health Organization for the detection of pulmonary TB, was evaluated to test its utility in 547 patients with suspected extrapulmonary tuberculosis. Five hundred forty-seven extrapulmonary specimens were split and processed simultaneously for both culture (solid and liquid) and Xpert testing. For culture, the sensitivity was low, 53% (150/283 specimens). Xpert sensitivity and specificity results were assessed in comparison to a composite reference standard made up of smear and culture results and clinical, radiological, and histological findings. The sensitivity of the Xpert assay was 81% (228/283 specimens) (64% [89/138] for smear-negative cases and 96% [139/145] for smear-positive cases), with a specificity of 99.6%. The sensitivity was found to be high for the majority of specimen types (63 to 100%) except for cerebrospinal fluid, the sensitivity of which was 29% (2/7 specimens). The Xpert test correctly identified 98% of phenotypic rifampin (RIF)-resistant cases and 94% of phenotypic RIF-susceptible cases. Sequencing of the 6 discrepant samples resolved 3 of them, resulting in an increased specificity of 98%. In conclusion, the results of this study suggest that the Xpert test also shows good potential for the diagnosis of extrapulmonary TB and that its ease of use makes it applicable for countries where TB is endemic.

GeneXpert--a game-changer for tuberculosis control?

Carlton Evans considers whether the new tuberculosis diagnostic test, GeneXpert, is the solution for TB control that it's said to be.

Rapid and accurate detection of Mycobacterium tuberculosis in sputum samples by Cepheid Xpert MTB/RIF assay--a clinical validation study

Background

A crucial impediment to global tuberculosis control is the lack of an accurate, rapid diagnostic test for detection of patients with active TB. A new, rapid diagnostic method, (Cepheid) Xpert MTB/RIF Assay, is an automated sample preparation and real-time PCR instrument, which was shown to have good potential as an alternative to current reference standard sputum microscopy and culture.

Methods

We performed a clinical validation study on diagnostic accuracy of the Xpert MTB/RIF Assay in a TB and HIV endemic setting. Sputum samples from 292 consecutively enrolled adults from Mbeya, Tanzania, with suspected TB were subject to analysis by the Xpert MTB/RIF Assay. The diagnostic performance of Xpert MTB/RIF Assay was compared to standard sputum smear microscopy and culture. Confirmed Mycobacterium tuberculosis in a positive culture was used as a reference standard for TB diagnosis.

Results

Xpert MTB/RIF Assay achieved 88.4% (95%CI = 78.4% to 94.9%) sensitivity among patients with a positive culture and 99% (95%CI = 94.7% to 100.0%) specificity in patients who had no TB. HIV status did not affect test performance in 172 HIV-infected patients (58.9% of all participants). Seven additional cases (9.1% of 77) were detected by Xpert MTB/RIF Assay among the group of patients with clinical TB who were culture negative. Within 45 sputum samples which grew non-tuberculous mycobacteria the assay's specificity was 97.8% (95%CI = 88.2% to 99.9%).

Conclusions

The Xpert MTB/RIF Assay is a highly sensitive, specific and rapid method for diagnosing TB which has potential to complement the current reference standard of TB diagnostics and increase its overall sensitivity. Its usefulness in detecting sputum smear and culture negative patients needs further study. Further evaluation in high burden TB and HIV areas under programmatic health care settings to ascertain applicability, cost-effectiveness, robustness and local acceptance are required.

Portable optoelectronic biosensing platform for identification of mycobacteria from the Mycobacterium tuberculosis complex

In this paper we report on the fabrication and performance of a portable and low cost optoelectronic platform integrating a double color tuned light emitting diode as light source, an amorphous/nanocrystalline silicon photodetector with a flat spectral response in the wavelength range from 520 nm to 630 nm and integrated electronic for signal acquisition and conditioning constituted by current to voltage converter, a filter and an amplification stage, followed by an analog to digital converter, with appropriate software for full automation to minimize human error. Incorporation of the double color tuned light emitting diode provides for a simple yet innovative solution to signal acquisition independently from the light intensity and/or solution concentration, while considerably decreasing production costs. Detection based on Au-nanoprobes constitutes the biorecognition step and allowed identification of specific sequences of Mycobacterium tuberculosis complex, namely Mycobacterium bovis and M. tuberculosis in biological samples.

Microscopic-observation drug susceptibility and thin layer agar assays for the detection of drug resistant tuberculosis: a systematic review and meta-analysis

BACKGROUND

Simple, rapid, and affordable tests are needed to detect drug resistance in Mycobacterium tuberculosis. We did a systematic review and meta-analysis to investigate the accuracy of microscopic-observation drug susceptibility (MODS) and thin layer agar (TLA) assays for rapid screening of patients at risk of drug-resistant tuberculosis.

METHODS

In accordance with protocols and methods recommended by the Cochrane Diagnostic Test Accuracy Working Group, we systematically searched PubMed, Embase, and Biosis for reports published between January, 1990, and February, 2009. We included studies investigating detection of drug resistance in M tuberculosis with the MODS or TLA assay, and in which an accepted reference standard was used. Data extracted from the studies were combined by use of bivariate random-effects regression models and hierarchical summary receiver operating characteristic curves to estimate sensitivity and specificity for detection of resistance to specific drugs.

FINDINGS

We identified 12 studies, of which nine investigated the MODS assay and three investigated the TLA assay. For the MODS assay of rifampicin resistance, pooled estimates were 98·0% (95% CI 94·5-99·3) for sensitivity and 99·4% (95·7-99·9) for specificity. For the MODS assay of isoniazid resistance with a 0·1 μg/mL cutoff, pooled sensitivity was 97·7% (94·4-99·1) and pooled specificity was 95·8% (88·1-98·6), but with a 0·4 μg/mL cutoff, sensitivity decreased to 90·0% (84·5-93·7) and specificity increased to 98·6% (96·9-99·4). All assessments of rifampicin and isoniazid resistance with the TLA assay yielded 100% accuracy. Mean turnaround time was 9·9 days (95% CI 4·1-15·8) for the MODS assay and 11·1 days (10·1-12·0) for the TLA assay.

INTERPRETATION

MODS and TLA assays are inexpensive, rapid alternatives to conventional methods for drug susceptibility testing of M tuberculosis. Our data and expert opinion informed WHO's recommendation for use of selected non-commercial drug susceptibility tests, including MODS, as an interim solution until capacity for genotypic or automated liquid culture drug susceptibility testing is developed.

FUNDING

Stop TB Department of WHO.

Stopping tuberculosis in the 21st century: goals and strategies

The Stop TB Strategy and the Global Plan to Stop TB were launched in 2006 to achieve the tuberculosis (TB)-related Millennium Development Goals and the Stop TB Partnership targets, and to address new challenges such as that of HIV-associated TB and multi-drug-resistant TB. This paper reviews the historical and recent progress in TB control to show what has changed since the introduction of directly observed therapy (DOTS) in the mid-1990s, why we needed the new strategy and what the global agenda is today. Major progress was seen in most countries in the last two decades. Globally, the estimated rates of TB prevalence and mortality are declining, but not quickly enough to reach the 2015 Stop TB Partnership targets of halving TB prevalence and death rates compared with 1990. In 2007, it was estimated that more than one-third of TB patients were not detected or properly treated under proper conditions. Enhancing case detection, while maintaining high treatment success rates, is essential to achieve the 2015 targets. The ultimate goal of TB control is the elimination of the disease as a public health problem. The Stop TB Partnership aims at eliminating TB by 2050 by reaching a global incidence of disease of less than one case per million population. This target will not be achieved unless TB control efforts are further intensified and effective and affordable new technologies to prevent both disease and infection are developed and rapidly introduced in all countries worldwide.

Biomarkers and diagnostics for tuberculosis: progress, needs, and translation into practice

Human infection with Mycobacterium tuberculosis can progress to active disease, be contained as latent infection, or be eradicated by the host response. Tuberculosis diagnostics classify a patient into one of these categories. These are not fixed distinct states, but rather are continua along which patients can move, and are affected by HIV infection, immunosuppressive therapies, antituberculosis treatments, and other poorly understood factors. Tuberculosis biomarkers-host or pathogen-specific-provide prognostic information, either for individual patients or study cohorts, about these outcomes. Tuberculosis case detection remains difficult, partly because of inaccurate diagnostic methods. Investments have yielded some progress in development of new diagnostics, although the existing pipeline is limited for tests for sputum-smear-negative cases, childhood tuberculosis, and accurate prediction of reactivation of latent tuberculosis. Despite new, sensitive, automated molecular platforms for detection of tuberculosis and drug resistance, a simple, inexpensive point-of-care test is still not available. The effect of any new tests will depend on the method and extent of their introduction, the strength of the laboratories, and the degree to which access to appropriate therapy follows access to diagnosis. Translation of scientific progress in biomarkers and diagnostics into clinical and public health programmes is possible-with political commitment, increased funding, and engagement of all stakeholders.

Tuberculosis control and elimination 2010-50: cure, care, and social development

Rapid expansion of the standardised approach to tuberculosis diagnosis and treatment that is recommended by WHO allowed more than 36 million people to be cured between 1995 and 2008, averting up to 6 million deaths. Yet tuberculosis remains a severe global public health threat. There are more than 9 million new cases every year worldwide, and the incidence rate is falling at less than 1% per year. Although the overall target related to the Millennium Development Goals of halting and beginning to reverse the epidemic might have already been reached in 2004, the more important long-term elimination target set for 2050 will not be met with present strategies and instruments. Several key challenges persist. Many vulnerable people do not have access to affordable services of sufficient quality. Technologies for diagnosis, treatment, and prevention are old and inadequate. Multidrug-resistant tuberculosis is a serious threat in many settings. HIV/AIDS continues to fuel the tuberculosis epidemic, especially in Africa. Furthermore, other risk factors and underlying social determinants help to maintain tuberculosis in the community. Acceleration of the decline towards elimination of this disease will need invigorated actions in four broad areas: continued scale-up of early diagnosis and proper treatment for all forms of tuberculosis in line with the Stop TB Strategy; development and enforcement of bold health-system policies; establishment of links with the broader development agenda; and promotion and intensification of research towards innovations.

Intestinal tuberculosis

PURPOSE OF REVIEW

Intestinal tuberculosis (TB) is increasing due partly to the HIV pandemic. Its clinical presentation mimics inflammatory conditions such as Crohn's disease and malignancies, which are becoming more prevalent, so the diagnosis is problematic.

RECENT FINDINGS

Greater awareness of intestinal TB is needed, both in countries where TB is endemic and developed countries with immigrant populations. Some strains of Mycobacterium tuberculosis are associated with more extrapulmonary disease and greater dissemination, thereby exacerbating the rise in HIV-associated extrathoracic TB. Recent retrospective and prospective studies are leading to the development of diagnostic algorithms. A wide range of imaging techniques is available for sampling and diagnosis. New biochemical, immunological and molecular diagnostic methods are being developed but must be standardized and validated. Developments in drug delivery will facilitate oral therapy even in patients suffering from malabsorption.

SUMMARY

There is an increasing consensus on the risk factors and clinical presentations of intestinal TB. Imaging techniques, coupled with fine needle biopsies, are useful aids to diagnosis, but most important is a greater awareness of the condition by clinicians.

Quality and reporting of diagnostic accuracy studies in TB, HIV and malaria: evaluation using QUADAS and STARD standards

BACKGROUND

Poor methodological quality and reporting are known concerns with diagnostic accuracy studies. In 2003, the QUADAS tool and the STARD standards were published for evaluating the quality and improving the reporting of diagnostic studies, respectively. However, it is unclear whether these tools have been applied to diagnostic studies of infectious diseases. We performed a systematic review on the methodological and reporting quality of diagnostic studies in TB, malaria and HIV.

METHODS

We identified diagnostic accuracy studies of commercial tests for TB, malaria and HIV through a systematic search of the literature using PubMed and EMBASE (2004-2006). Original studies that reported sensitivity and specificity data were included. Two reviewers independently extracted data on study characteristics and diagnostic accuracy, and used QUADAS and STARD to evaluate the quality of methods and reporting, respectively.

FINDINGS

Ninety (38%) of 238 articles met inclusion criteria. All studies had design deficiencies. Study quality indicators that were met in less than 25% of the studies included adequate description of withdrawals (6%) and reference test execution (10%), absence of index test review bias (19%) and reference test review bias (24%), and report of uninterpretable results (22%). In terms of quality of reporting, 9 STARD indicators were reported in less than 25% of the studies: methods for calculation and estimates of reproducibility (0%), adverse effects of the diagnostic tests (1%), estimates of diagnostic accuracy between subgroups (10%), distribution of severity of disease/other diagnoses (11%), number of eligible patients who did not participate in the study (14%), blinding of the test readers (16%), and description of the team executing the test and management of indeterminate/outlier results (both 17%). The use of STARD was not explicitly mentioned in any study. Only 22% of 46 journals that published the studies included in this review required authors to use STARD.

CONCLUSION

Recently published diagnostic accuracy studies on commercial tests for TB, malaria and HIV have moderate to low quality and are poorly reported. The more frequent use of tools such as QUADAS and STARD may be necessary to improve the methodological and reporting quality of future diagnostic accuracy studies in infectious diseases.

Recent advances in diagnostic microbiology

The past decade has seen a surge in the development of a variety of molecular diagnostics designed to rapidly identify or characterize medically important microorganisms. We briefly review important advances in molecular microbiology, and then discuss specific assays that have been implemented in clinical microbiology laboratories throughout the country. We also discuss emerging methods and technologies that will soon be more widely used for the prompt and accurate detection of the agents of infectious diseases.

Blinded evaluation of commercial urinary lipoarabinomannan for active tuberculosis: a pilot study

SETTING

Urine antigen testing is an attractive strategy for the diagnosis of active tuberculosis (TB), but accuracy data are scarce.

OBJECTIVE

To prospectively evaluate the diagnostic performance of commercial urinary lipoarabinomannan (LAM) antigen testing for active TB among pulmonary and extra-pulmonary TB suspects.

DESIGN

Prospective blinded evaluation of 200 adult TB suspects at a tertiary referral hospital in India. Reference standards included culture and clinical diagnosis.

RESULTS

Patients were 61% male (mean age 40.4 years): 8.5% were human immunodeficiency virus (HIV) infected and 47 of 200 (23.5%) were culture-positive for TB. Compared to positivity on either Löwenstein-Jensen (LJ) or BACTEC cultures, LAM sensitivity was 17.8% (95%CI 8.5-32.6), while specificity was 87.7% (95%CI 81.3-92.3). Compared to positivity on both LJ and BACTEC, LAM sensitivity was 5.8% (95%CI 12.5-44.9), with a specificity of 88.8% (95%CI 82.7-92.9). Compared to the clinical diagnosis, LAM sensitivity was 20.0% (95%CI 1.1-70.1), with a specificity of 83.3% (95%CI 50.9-97.0). HIV and smear status did not influence test accuracy.

CONCLUSION

In its current form, LAM is insensitive for the diagnosis of active TB, although its specificity is adequate.

A pilot study of short-duration sputum pretreatment procedures for optimizing smear microscopy for tuberculosis

BACKGROUND

Direct sputum smear microscopy for tuberculosis (TB) lacks sensitivity for the detection of acid fast bacilli. Sputum pretreatment procedures may enhance sensitivity. We did a pilot study to compare the diagnostic accuracy and incremental yield of two short-duration (<1 hour) sputum pretreatment procedures to optimize direct smears among patients with suspected TB at a referral hospital in India.

METHODOLOGY/FINDINGS

Blinded laboratory comparison of bleach and universal sediment processing (USP) pretreated centrifuged auramine smears to direct Ziehl-Neelsen (ZN) and direct auramine smears and to solid (Loweinstein-Jensen (LJ)) and liquid (BACTEC 460) culture. 178 pulmonary and extrapulmonary TB suspects were prospectively recruited during a one year period. Thirty six (20.2%) were positive by either solid or liquid culture. Direct ZN smear detected 22 of 36 cases and direct auramine smears detected 26 of 36 cases. Bleach and USP centrifugation detected 24 cases each, providing no incremental yield beyond direct smears. When compared to combined culture, pretreated smears were not more sensitive than direct smears (66.6% vs 61.1 (ZN) or 72.2 (auramine)), and were not more specific (92.3% vs 93.0 (ZN) or 97.2 (auramine).

CONCLUSIONS/SIGNIFICANCE

Short duration sputum pretreatment with bleach and USP centrifugation did not increase yield as compared to direct sputum smears. Further work is needed to confirm this in a larger study and also determine if longer duration pre-treatment might be effective in optimizing smear microscopy for TB.

Improvement in mycobacterial yield and reduced time to detection in pediatric samples by use of a nutrient broth growth supplement

There is an urgent need to improve the methods used for the bacteriological diagnosis of childhood mycobacterial disease. This study compared the mycobacterial yields and the times to detection (in days) of mycobacteria in pediatric clinical specimens by using Mycobacterial Growth Indicator Tubes (MGITs) and solid Löwenstein-Jensen (LJ) slants with and without a nutrient broth supplement. A total of 801 specimens from 493 patients were processed: 82.8% were gastric aspirate specimens, 15.6% were sputum specimens, and 1.6% were fine-needle-aspiration biopsy specimens. The mycobacterial yield obtained with MGITs (with and without nutrient broth) was 11.0%, and that obtained with LJ slants was 1.6% (P < 0.001). Of the 88 positive cultures, 62 were detected in MGITs and 73 were detected in MGITs supplemented with nutrient broth (P = 0.11). The mean time to detection in MGITs (without nutrient broth) was 18.5 days, whereas it was 12.4 days in MGITs with nutrient broth (P < 0.001). Supplementation of standard MGITs improved the mycobacterial yield and significantly reduced the time to detection of mycobacteria in pediatric samples.

The clinical value of new diagnostic tools for tuberculosis

Barriers to global tuberculosis (TB) control include multidrug resistance, HIV infection, and weak health systems. Case detection is critical to TB control and is affected by all three of these. Currently, most low- and middle-income countries (LMICs) rely on direct sputum smear microscopy for diagnosis. Modern culture methods and molecular tests, previously considered too complex or too expensive for implementation in LMICs, are now being introduced there in parallel with a global effort to strengthen laboratories. It remains to be seen whether services based on these tools can be made widely accessible to patients. New point-of-care tests for TB are urgently needed but cannot be expected in the near future. In the meantime, diagnostic tools based on optimized smear microscopy, although less sensitive than reference laboratory tests, may be more accessible and have more impact on case finding. It is a matter of urgency that these improved microscopy services be integrated with services based on rapid methods that can identify multidrug-resistant cases.