Guidance for the Evaluation of Tuberculosis Diagnostics That Meet the World Health Organization (WHO) Target Product Profiles: An Introduction to WHO Process and Study Design Principles

Existing high-priority target product profiles (TPPs) of the World Health Organization (WHO) establish important needs for tuberculosis (TB) diagnostic development. Building on this earlier work, this guidance series aims to provide study guidance for performing accuracy studies of novel diagnostic products that may meet the 4 high-priority WHO TPPs and thus enable adequate evidence generation to inform a WHO evidence review process. Diagnostic accuracy studies represent a fundamental step in the validation of all tests. Unfortunately, such studies often have limitations in design, execution, and reporting, leading to low certainty of the evidence about true test performance, which can delay or impede policy and scale-up decisions. This introductory paper outlines the following: (1) the purpose of this series of papers on study guidance; (2) WHO evidence needs and process for the development of policy guidelines for new TB diagnostic tests; and (3) study design considerations, ie, general diagnostic study considerations, intended use of test and role in the clinical pathway, choice of population and setting, index-test specific issues, suitable reference standard and comparators, study flow and specimen issues, and finally key issues beyond accuracy that should be considered. The other 4 papers in this series will provide more detailed guidance for each of the 4 WHO high-priority TPPs. By increasing the clarity around the clinical evaluation needs for tests that have the potential to meet the TPP specifications, we hope to support harmonized evidence generation and enable the WHO review process towards meeting the WHO End TB Strategy targets for reducing the incidence and mortality associated with TB.

Guidance for Studies Evaluating the Accuracy of Biomarker-Based Nonsputum Tests to Diagnose Tuberculosis

The World Health Organization's (WHO) "End TB" strategy calls for development and implementation of novel tuberculosis (TB) diagnostics. Sputum-based diagnostics are challenging to implement and often less sensitive in high-priority populations. Nonsputum, biomarker-based tests may facilitate TB testing at lower levels of the healthcare system, accelerate treatment initiation, and improve outcomes. We provide guidance on the design of diagnostic accuracy studies evaluating nonsputum, biomarker-based tests within the context of WHO's target product profile for such tests. Study designs should account for the intended use when choosing the study population, setting, and reference standards. Although adults with respiratory symptoms may be an initial target population, other high-priority populations regardless of symptoms-including people living with human immunodeficiency virus, those unable to produce sputum samples or with extrapulmonary TB, household contacts, and children-should be considered. Studies beyond diagnostic accuracy that evaluate feasibility and population-level impacts are also needed. A biomarker-based diagnostic may be critical to ending the TB epidemic, but requires appropriate validation before implementation.

Guidance for Studies Evaluating the Accuracy of Rapid Tuberculosis Drug-Susceptibility Tests

The development and implementation of rapid molecular diagnostics for tuberculosis (TB) drug-susceptibility testing is critical to inform treatment of patients and to prevent the emergence and spread of resistance. Optimal trial planning for existing tests and those in development will be critical to rapidly gather the evidence necessary to inform World Health Organization review and to support potential policy recommendations. The evidence necessary includes an assessment of the performance for TB and resistance detection as well as an assessment of the operational characteristics of these platforms. The performance assessment should include analytical studies to confirm the limit of detection and assay ability to detect mutations conferring resistance across globally representative strains. The analytical evaluation is typically followed by multisite clinical evaluation studies to confirm diagnostic performance in sites and populations of intended use. This paper summarizes the considerations for the design of these analytical and clinical studies.

Standardised shorter regimens versus individualised longer regimens for rifampin- or multidrug-resistant tuberculosis

We sought to compare the effectiveness of two World Health Organization (WHO)-recommended regimens for the treatment of rifampin- or multidrug-resistant (RR/MDR) tuberculosis (TB): a standardised regimen of 9-12 months (the "shorter regimen") and individualised regimens of ≥20 months ("longer regimens").We collected individual patient data from observational studies identified through systematic reviews and a public call for data. We included patients meeting WHO eligibility criteria for the shorter regimen: not previously treated with second-line drugs, and with fluoroquinolone- and second-line injectable agent-susceptible RR/MDR-TB. We used propensity score matched, mixed effects meta-regression to calculate adjusted odds ratios and adjusted risk differences (aRDs) for failure or relapse, death within 12 months of treatment initiation and loss to follow-up.We included 2625 out of 3378 (77.7%) individuals from nine studies of shorter regimens and 2717 out of 13 104 (20.7%) individuals from 53 studies of longer regimens. Treatment success was higher with the shorter regimen than with longer regimens (pooled proportions 80.0% versus 75.3%), due to less loss to follow-up with the former (aRD -0.15, 95% CI -0.17- -0.12). The risk difference for failure or relapse was slightly higher with the shorter regimen overall (aRD 0.02, 95% CI 0-0.05) and greater in magnitude with baseline resistance to pyrazinamide (aRD 0.12, 95% CI 0.07-0.16), prothionamide/ethionamide (aRD 0.07, 95% CI -0.01-0.16) or ethambutol (aRD 0.09, 95% CI 0.04-0.13).In patients meeting WHO criteria for its use, the standardised shorter regimen was associated with substantially less loss to follow-up during treatment compared with individualised longer regimens and with more failure or relapse in the presence of resistance to component medications. Our findings support the need to improve access to reliable drug susceptibility testing.

Guidance for Studies Evaluating the Accuracy of Sputum-Based Tests to Diagnose Tuberculosis

Tests that can replace sputum smear microscopy have been identified as a top priority diagnostic need for tuberculosis by the World Health Organization. High-quality evidence on diagnostic accuracy for tests that may meet this need is an essential requirement to inform decisions about policy and scale-up. However, test accuracy studies are often of low and inconsistent quality and poorly reported, leading to uncertainty about true test performance. Here we provide guidance for the design of diagnostic test accuracy studies of sputum smear-replacement tests. Such studies should have a cross-sectional or cohort design, enrolling either a consecutive series or a random sample of patients who require evaluation for tuberculosis. Adults with respiratory symptoms are the target population. The reference standard should at a minimum be a single, automated, liquid culture, but additional cultures, follow-up, clinical case definition, and specific measures to understand discordant results should also be included. Inclusion of smear microscopy and Xpert MTB/RIF (or MTB/RIF Ultra) as comparators is critical to allow broader comparability and generalizability of results, because disease spectrum can vary between studies and affects relative test performance. Given the complex nature of sputum (the primary specimen type used for pulmonary TB), careful design and reporting of the specimen flow is essential. Test characteristics other than accuracy (such as feasibility, implementation considerations, and data on impact on patient, population and health systems outcomes) are also important aspects.

Genetic sequencing for surveillance of drug resistance in tuberculosis in highly endemic countries: a multi-country population-based surveillance study

Background

In many countries, regular monitoring of the emergence of resistance to anti-tuberculosis drugs is hampered by the limitations of phenotypic testing for drug susceptibility. We therefore evaluated the use of genetic sequencing for surveillance of drug resistance in tuberculosis.

Methods

Population-level surveys were done in hospitals and clinics in seven countries (Azerbaijan, Bangladesh, Belarus, Pakistan, Philippines, South Africa, and Ukraine) to evaluate the use of genetic sequencing to estimate the resistance of Mycobacterium tuberculosis isolates to rifampicin, isoniazid, ofloxacin, moxifloxacin, pyrazinamide, kanamycin, amikacin, and capreomycin. For each drug, we assessed the accuracy of genetic sequencing by a comparison of the adjusted prevalence of resistance, measured by genetic sequencing, with the true prevalence of resistance, determined by phenotypic testing.

Findings

Isolates were taken from 7094 patients with tuberculosis who were enrolled in the study between November, 2009, and May, 2014. In all tuberculosis cases, the overall pooled sensitivity values for predicting resistance by genetic sequencing were 91% (95% CI 87–94) for rpoB (rifampicin resistance), 86% (74–93) for katG, inhA, and fabG promoter combined (isoniazid resistance), 54% (39–68) for pncA (pyrazinamide resistance), 85% (77–91) for gyrA and gyrB combined (ofloxacin resistance), and 88% (81–92) for gyrA and gyrB combined (moxifloxacin resistance). For nearly all drugs and in most settings, there was a large overlap in the estimated prevalence of drug resistance by genetic sequencing and the estimated prevalence by phenotypic testing.

Interpretation

Genetic sequencing can be a valuable tool for surveillance of drug resistance, providing new opportunities to monitor drug resistance in tuberculosis in resource-poor countries. Before its widespread adoption for surveillance purposes, there is a need to standardise DNA extraction methods, recording and reporting nomenclature, and data interpretation.

Funding

Bill & Melinda Gates Foundation, United States Agency for International Development, Global Alliance for Tuberculosis Drug Development.

Fungaemia caused by obstructive renal candida bezoars leads to bilateral chorioretinitis: a case report

BACKGROUND

Renal fungal bezoars are remarkably rare and mostly occur in immunodeficient patients. Only a small number of cases with immunocompetent patients have been published so far. The published treatment approaches comprised systemic antimycotic therapy and surgical or minimal invasive removal of the fungal balls. In some cases irrigation of the renal duct system with amphotericin B was performed. By obstruction of the urinary tract bezoars can lead to infected hydronephrosis and severe urosepsis with high lethality. Fungaemia can cause fungal colonization in different distant organs. Fulminant chorioretinitis and irreversible visual impairment can be the consequence of ocular fundus colonization. The following report highlights that a co-operation between urologists and ophthalmologists is absolutely indispensible in case of fungaemia.

CASE PRESENTATION

Hereinafter we describe a case of an immunocompetent 56 years old woman, presenting with flank pain and shivering. The diagnosis turned out to be difficult due to initially negative urine culture. The fungaemia caused by obstructive nephropathy led to bilateral candida chorioretinitis. The patient was treated with intravenous amphotericin b and the bezoar was removed by percutaneous "nephrolitholapaxy". After two months, a follow up revealed the patient felt well, chorioretinal lesions regressed and urine culture did not show any fungal growth.

CONCLUSION

To the best of our knowledge, this is the first case reporting on obstructive renal bezoars, which lead to haematogenous fungus spread and bilateral chorioretinitis. It points out that extensive ophthalmologic examination should be performed in case of fungaemia even if the patient is not suffering from any visual impairment.

World Health Organization treatment guidelines for drug-resistant tuberculosis, 2016 update

Antimicrobial resistance is a major global concern. Tuberculosis (TB) strains resistant to rifampicin and other TB medicines challenge patient survival and public health. The World Health Organization (WHO) has published treatment guidelines for drug-resistant TB since 1997 and last updated them in 2016 based on reviews of aggregated and individual patient data from published and unpublished studies. An international expert panel formulated recommendations following the GRADE approach. The new WHO guidelines recommend a standardised 9–12 months shorter treatment regimen as first choice in patients with multidrug- or rifampicin-resistant TB (MDR/RR-TB) strains not resistant to fluoroquinolones or second-line injectable agents; resistance to these two classes of core second-line medicines is rapidly detectable with molecular diagnostics also approved by WHO in 2016. The composition of longer regimens for patients ineligible for the shorter regimen was modified. A first-ever meta-analysis of individual paediatric patient data allowed treatment recommendations for childhood MDR/RR-TB to be made. Delamanid is now also recommended in patients aged 6–17 years. Partial lung resection is a recommended option in MDR/RR-TB care. The 2016 revision highlighted the continued shortage of high-quality evidence and implementation research, and reiterated the need for clinical trials and best-practice studies to improve MDR/RR-TB patient treatment outcomes and strengthen policy.

The latest WHO recommendations for the treatment of multidrug- and rifampicin-resistant tuberculosis (MDR/RR-TB)http://ow.ly/Lj5K307XZ7h

Current tools available for the diagnosis of drug-resistant tuberculosis

Drug-resistant tuberculosis (DR-TB) poses a major threat to control of tuberculosis worldwide. Diagnosis and treatment of DR-TB are considerably more difficult than for drug-susceptible tuberculosis (TB) and require higher level infrastructure and proficiency from laboratory specialists and clinicians. The World Health Organization (WHO) End TB Strategy calls for early diagnosis and initiation of appropriate treatment of all persons of all ages with any form of drug-susceptible TB or DR-TB. This requires ensuring access to WHO-recommended rapid diagnostics and universal drug susceptibility testing (DST) for all persons with signs and symptoms of TB. There are a number of laboratory tools available for diagnosis of DR-TB, including phenotypic culture-based DST as well as molecular methods. Optimal and complementary use of the available diagnostic tools at the different levels of the tiered network of TB laboratories, as well as correct interpretation of the diagnostic results provided by them is critical for accurate and timely diagnosis of DR-TB thus enabling effective treatment and care of patients.

Population-based resistance of Mycobacterium tuberculosis isolates to pyrazinamide and fluoroquinolones: results from a multicountry surveillance project

Background

Pyrazinamide and fluoroquinolones are essential antituberculosis drugs in new rifampicin-sparing regimens. However, little information about the extent of resistance to these drugs at the population level is available.

Methods

In a molecular epidemiology analysis, we used population-based surveys from Azerbaijan, Bangladesh, Belarus, Pakistan, and South Africa to investigate resistance to pyrazinamide and fluoroquinolones among patients with tuberculosis. Resistance to pyrazinamide was assessed by gene sequencing with the detection of resistance-conferring mutations in the pncA gene, and susceptibility testing to fluoroquinolones was conducted using the MGIT system.

Findings

Pyrazinamide resistance was assessed in 4972 patients. Levels of resistance varied substantially in the surveyed settings (3·0–42·1%). In all settings, pyrazinamide resistance was significantly associated with rifampicin resistance. Among 5015 patients who underwent susceptibility testing to fluoroquinolones, proportions of resistance ranged from 1·0–16·6% for ofloxacin, to 0·5–12·4% for levofloxacin, and 0·9–14·6% for moxifloxacin when tested at 0·5 μg/mL. High levels of ofloxacin resistance were detected in Pakistan. Resistance to moxifloxacin and gatifloxacin when tested at 2 μg/mL was low in all countries.

Interpretation

Although pyrazinamide resistance was significantly associated with rifampicin resistance, this drug may still be effective in 19–63% of patients with rifampicin-resistant tuberculosis. Even though the high level of resistance to ofloxacin found in Pakistan is worrisome because it might be the expression of extensive and unregulated use of fluoroquinolones in some parts of Asia, the negligible levels of resistance to fourth-generation fluoroquinolones documented in all survey sites is an encouraging finding. Rational use of this class of antibiotics should therefore be ensured to preserve its effectiveness.

Funding

Bill & Melinda Gates Foundation, United States Agency for International Development, Global Alliance for Tuberculosis Drug Development.

Digital health for the End TB Strategy: developing priority products and making them work

In 2014, the World Health Organization (WHO) developed the End TB Strategy in response to a World Health Assembly Resolution requesting Member States to end the worldwide epidemic of tuberculosis (TB) by 2035. For the strategy's objectives to be realised, the next 20 years will need novel solutions to address the challenges posed by TB to health professionals, and to affected people and communities. Information and communication technology presents opportunities for innovative approaches to support TB efforts in patient care, surveillance, programme management and electronic learning. The effective application of digital health products at a large scale and their continued development need the engagement of TB patients and their caregivers, innovators, funders, policy-makers, advocacy groups, and affected communities.

In April 2015, WHO established its Global Task Force on Digital Health for TB to advocate and support the development of digital health innovations in global efforts to improve TB care and prevention. We outline the group's approach to stewarding this process in alignment with the three pillars of the End TB Strategy. The supplementary material of this article includes target product profiles, as developed by early 2016, defining nine priority digital health concepts and products that are strategically positioned to enhance TB action at the country level.

Priority digital health products will be profiled and developed to support the scale-up of WHO's End TB Strategyhttp://ow.ly/4mRRjR

Translational Research for Tuberculosis Elimination: Priorities, Challenges, and Actions

Christian Lienhardt and colleagues describe the research efforts needed to end the global tuberculosis epidemic by 2035.

Management of latent Mycobacterium tuberculosis infection: WHO guidelines for low tuberculosis burden countries

Latent tuberculosis infection (LTBI) is characterised by the presence of immune responses to previously acquired Mycobacterium tuberculosis infection without clinical evidence of active tuberculosis (TB). Here we report evidence-based guidelines from the World Health Organization for a public health approach to the management of LTBI in high risk individuals in countries with high or middle upper income and TB incidence of <100 per 100 000 per year. The guidelines strongly recommend systematic testing and treatment of LTBI in people living with HIV, adult and child contacts of pulmonary TB cases, patients initiating anti-tumour necrosis factor treatment, patients receiving dialysis, patients preparing for organ or haematological transplantation, and patients with silicosis. In prisoners, healthcare workers, immigrants from high TB burden countries, homeless persons and illicit drug users, systematic testing and treatment of LTBI is conditionally recommended, according to TB epidemiology and resource availability. Either commercial interferon-gamma release assays or Mantoux tuberculin skin testing could be used to test for LTBI. Chest radiography should be performed before LTBI treatment to rule out active TB disease. Recommended treatment regimens for LTBI include: 6 or 9 month isoniazid; 12 week rifapentine plus isoniazid; 3-4 month isoniazid plus rifampicin; or 3-4 month rifampicin alone.

Institutional Tuberculosis Transmission. Controlled Trial of Upper Room Ultraviolet Air Disinfection: A Basis for New Dosing Guidelines

RATIONALE

Transmission is driving the global tuberculosis epidemic, especially in congregate settings. Worldwide, natural ventilation is the most common means of air disinfection, but it is inherently unreliable and of limited use in cold climates. Upper room germicidal ultraviolet (UV) air disinfection with air mixing has been shown to be highly effective, but improved evidence-based dosing guidelines are needed.

OBJECTIVES

To test the efficacy of upper room germicidal air disinfection with air mixing to reduce tuberculosis transmission under real hospital conditions, and to define the application parameters responsible as a basis for proposed new dosing guidelines.

METHODS

Over an exposure period of 7 months, 90 guinea pigs breathed only untreated exhaust ward air, and another 90 guinea pigs breathed only air from the same six-bed tuberculosis ward on alternate days when upper room germicidal air disinfection was turned on throughout the ward.

MEASUREMENTS AND MAIN RESULTS

The tuberculin skin test conversion rates (>6 mm) of the two chambers were compared. The hazard ratio for guinea pigs in the control chamber converting their skin test to positive was 4.9 (95% confidence interval, 2.8-8.6), with an efficacy of approximately 80%.

CONCLUSIONS

Upper room germicidal UV air disinfection with air mixing was highly effective in reducing tuberculosis transmission under hospital conditions. These data support using either a total fixture output (rather than electrical or UV lamp wattage) of 15-20 mW/m(3) total room volume, or an average whole-room UV irradiance (fluence rate) of 5-7 μW/cm(2), calculated by a lighting computer-assisted design program modified for UV use.

Defining the needs for next generation assays for tuberculosis

To accelerate the fight against tuberculosis, major diagnostic challenges need to be addressed urgently. Post-2015 targets are unlikely to be met without the use of novel diagnostics that are more accurate and can be used closer to where patients first seek care in affordable diagnostic algorithms. This article describes the efforts by the stakeholder community that led to the identification of the high-priority diagnostic needs in tuberculosis. Subsequently target product profiles for the high-priority diagnostic needs were developed and reviewed in a World Health Organization (WHO)-led consensus meeting. The high-priority diagnostic needs included (1) a sputum-based replacement test for smear-microscopy; (2) a non-sputum-based biomarker test for all forms of tuberculosis, ideally suitable for use at levels below microscopy centers; (3) a simple, low cost triage test for use by first-contact care providers as a rule-out test, ideally suitable for use by community health workers; and (4) a rapid drug susceptibility test for use at the microscopy center level. The developed target product profiles, along with complimentary work presented in this supplement, will help to facilitate the interaction between the tuberculosis community and the diagnostics industry with the goal to lead the way toward the post-2015 global tuberculosis targets.

Multidrug-resistant tuberculosis around the world: what progress has been made?

Multidrug-resistant tuberculosis (MDR-TB) (resistance to at least isoniazid and rifampicin) will influence the future of global TB control. 88% of estimated MDR-TB cases occur in middle- or high-income countries, and 60% occur in Brazil, China, India, the Russian Federation and South Africa.

The World Health Organization collects country data annually to monitor the response to MDR-TB. Notification, treatment enrolment and outcome data were summarised for 30 countries, accounting for >90% of the estimated MDR-TB cases among notified TB cases worldwide.

In 2012, a median of 14% (interquartile range 6–50%) of estimated MDR-TB cases were notified in the 30 countries studied. In 15 of the 30 countries, the number of patients treated for MDR-TB in 2012 (71 681) was >50% higher than in 2011. Median treatment success was 53% (interquartile range 40–70%) in the 25 countries reporting data for 30 021 MDR-TB cases who started treatment in 2010.

Although progress has been noted in the expansion of MDR-TB care, urgent efforts are required in order to provide wider access to diagnosis and treatment in most countries with the highest burden of MDR-TB.

A wider adoption of effective diagnostics, treatment and preventive measures is needed to control MDR-TB globallyhttp://ow.ly/zwZWr

Treatment outcomes of patients with multidrug-resistant and extensively drug-resistant tuberculosis according to drug susceptibility testing to first- and second-line drugs: an individual patient data meta-analysis

BACKGROUND

Individualized treatment for multidrug-resistant (MDR) tuberculosis and extensively drug-resistant (XDR) tuberculosis depends upon reliable and valid drug susceptibility testing (DST) for pyrazinamide, ethambutol, and second-line tuberculosis drugs. However, the reliability of these tests is uncertain, due to unresolved methodological issues. We estimated the association of DST results for pyrazinamide, ethambutol, and second-line drugs with treatment outcomes in patients with MDR tuberculosis and XDR tuberculosis.

METHODS

We conducted an analysis of individual patient data assembled from 31 previously published cohort studies of patients with MDR and XDR tuberculosis. We used data on patients' clinical characteristics including DST results, treatment received, outcomes, and laboratory methods in each center.

RESULTS

DST methods and treatment regimens used in different centers varied considerably. Among 8955 analyzed patients, in vitro susceptibility to individual drugs was consistently and significantly associated with higher odds of treatment success (compared with resistance to the drug), if that drug was used in the treatment regimen. Various adjusted and sensitivity analyses suggest that this was not explained by confounding. The adjusted odds of treatment success for ethambutol, pyrazinamide, and the group 4 drugs ranged from 1.7 to 2.3, whereas for second-line injectables and fluoroquinolones, odds ranged from 2.4 to 4.6.

CONCLUSIONS

DST for ethambutol, pyrazinamide, and second-line tuberculosis drugs appears to provide clinically useful information to guide selection of treatment regimens for MDR and XDR tuberculosis.

Safety and availability of clofazimine in the treatment of multidrug and extensively drug-resistant tuberculosis: analysis of published guidance and meta-analysis of cohort studies

OBJECTIVES

Given the spread of multidrug-resistant tuberculosis (MDR-TB), new therapies are urgently needed, including the repurposing of existing drugs. We aimed to assess key considerations for the clinical and programmatic use of clofazimine (Cfz), a riminophenazine with antimycobacterial activity currently used to treat leprosy.

DESIGN

Fixed and random effects meta-analysis of cohort studies and systematic review.

SETTING

Electronic and manual searches were combined.

INCLUSION CRITERIA

Observational studies on treatment of multidrug-resistant and extremely drug-resistant tuberculosis with Cfz or a Cfz-containing regimen, and published guidance and documents relating to cost and availability were eligible.

RESULTS

5 observational studies enrolled 861 patients, of which 602 received Cfz. The pooled proportion of adverse drug reactions requiring discontinuation of Cfz treatment was 0.1% (95% CI (0.0 to 0.6%)), and the median frequency of all adverse events was 5.1%. Cfz showed in vitro efficacy against Mycobacterium tuberculosis, and Cfz-containing regimens may have had a useful role in the treatment of patients with drug-resistant strains and who had limited alternative treatment options. However, Cfz uptake remains insufficient to meet global needs; there is only one internationally quality-assured manufacturer, which produces a limited quantity of the drug prioritised for treatment of leprosy, the only indication for which the drug is registered.

CONCLUSIONS

While the data were limited, Cfz was associated with a risk for adverse drug reactions comparable to that of first-line TB treatment, which could be reasonably managed under programmatic conditions. However, low market availability and high cost are important barriers to access to Cfz for patients with MDR-TB.

Challenges and controversies in defining totally drug-resistant tuberculosis

In March 2012, in response to reports of tuberculosis (TB) resistant to all anti-TB drugs, the World Health Organization convened an expert consultation that identified issues to be resolved before defining a new category of highly drug-resistant TB. Proposed definitions are ambiguous, and extensive drug resistance is encompassed by the already defined extensively drug-resistant (XDR) TB. There is no evidence that proposed totally resistant TB differs from strains encompassed by XDR TB. Susceptibility tests for several drugs are poorly reproducible. Few laboratories can test all drugs, and there is no consensus list of all anti-TB drugs. Many drugs are used off-label for highly drug resistant TB, and new drugs formulated to combat resistant strains would render the proposed category obsolete. Labeling TB strains as totally drug resistant might lead providers to think infected patients are untreatable. These challenges must be addressed before defining a new category for highly drug-resistant TB.

Rapid molecular TB diagnosis: evidence, policy making and global implementation of Xpert MTB/RIF

If tuberculosis (TB) is to be eliminated as a global health problem in the foreseeable future, improved detection of patients, earlier diagnosis and timely identification of rifampicin resistance will be critical. New diagnostics released in recent years have improved this perspective but they require investments in laboratory infrastructure, biosafety and staff specialisation beyond the means of many resource-constrained settings where most patients live. Xpert MTB/RIF, a new assay employing automated nucleic acid amplification to detect Mycobacterium tuberculosis, as well as mutations that confer rifampicin resistance, holds the promise to largely overcome these operational challenges. In this article we position Xpert MTB/RIF in today's TB diagnostic landscape and describe its additional potential as an adjunct to surveillance and surveys, taking into account considerations of pricing and ethics. In what could serve as a model for the future formulation of new policy on diagnostics, we trace the unique process by which the World Health Organization consulted international expertise and systematically assessed published evidence and freshly emerging experience from the field ahead of its endorsement of the Xpert MTB/RIF technology in 2010, summarise subsequent research findings and guidance on who to test and how, and provide perspectives on scaling up the new technology.

Scaling up interventions to achieve global tuberculosis control: progress and new developments

Tuberculosis is still one of the most important causes of death worldwide. The 2010 Lancet tuberculosis series provided a comprehensive overview of global control efforts and challenges. In this update we review recent progress. With improved control efforts, the world and most regions are on track to achieve the Millennium Development Goal of decreasing tuberculosis incidence by 2015, and the Stop TB Partnership target of halving 1990 mortality rates by 2015; the exception is Africa. Despite these advances, full scale-up of tuberculosis and HIV collaborative activities remains challenging and emerging drug-resistant tuberculosis is a major threat. Recognition of the effect that non-communicable diseases--such as smoking-related lung disease, diet-related diabetes mellitus, and alcohol and drug misuse--have on individual vulnerability, as well as the contribution of poor living conditions to community vulnerability, shows the need for multidisciplinary approaches. Several new diagnostic tests are being introduced in endemic countries and for the first time in 40 years a coordinated portfolio of promising new tuberculosis drugs exists. However, none of these advances offer easy solutions. Achievement of international tuberculosis control targets and maintenance of these gains needs optimum national health policies and services, with ongoing investment into new approaches and strategies. Despite growing funding in recent years, a serious shortfall persists. International and national financial uncertainty places gains at serious risk. Perseverance and renewed commitment are needed to achieve global control of tuberculosis, and ultimately, its elimination.

Tuberculosis diagnostics and biomarkers: needs, challenges, recent advances, and opportunities

Tuberculosis is unique among the major infectious diseases in that it lacks accurate rapid point-of-care diagnostic tests. Failure to control the spread of tuberculosis is largely due to our inability to detect and treat all infectious cases of pulmonary tuberculosis in a timely fashion, allowing continued Mycobacterium tuberculosis transmission within communities. Currently recommended gold-standard diagnostic tests for tuberculosis are laboratory based, and multiple investigations may be necessary over a period of weeks or months before a diagnosis is made. Several new diagnostic tests have recently become available for detecting active tuberculosis disease, screening for latent M. tuberculosis infection, and identifying drug-resistant strains of M. tuberculosis. However, progress toward a robust point-of-care test has been limited, and novel biomarker discovery remains challenging. In the absence of effective prevention strategies, high rates of early case detection and subsequent cure are required for global tuberculosis control. Early case detection is dependent on test accuracy, accessibility, cost, and complexity, but also depends on the political will and funder investment to deliver optimal, sustainable care to those worst affected by the tuberculosis and human immunodeficiency virus epidemics. This review highlights unanswered questions, challenges, recent advances, unresolved operational and technical issues, needs, and opportunities related to tuberculosis diagnostics.

Patient- and provider-level risk factors associated with default from tuberculosis treatment, South Africa, 2002: a case-control study

BACKGROUND

Persons who default from tuberculosis treatment are at risk for clinical deterioration and complications including worsening drug resistance and death. Our objective was to identify risk factors associated with tuberculosis (TB) treatment default in South Africa.

METHODS

We conducted a national retrospective case control study to identify factors associated with treatment default using program data from 2002 and a standardized patient questionnaire. We defined default as interrupting TB treatment for two or more consecutive months during treatment. Cases were a sample of registered TB patients receiving treatment under DOTS that defaulted from treatment. Controls were those who began therapy and were cured, completed or failed treatment. Two respective multivariable models were constructed, stratified by history of TB treatment (new and re-treatment patients), to identify independent risk factors associated with default.

RESULTS

The sample included 3165 TB patients from 8 provinces; 1164 were traceable and interviewed (232 cases and 932 controls). Significant risk factors associated with default among both groups included poor health care worker attitude (new: AOR 2.1, 95% CI 1.1-4.4; re-treatment: AOR 12, 95% CI 2.2-66.0) and changing residence during TB treatment (new: AOR 2.0, 95% CI 1.1-3.7; re-treatment: AOR 3.4, 95% CI 1.1-9.9). Among new patients, cases were more likely than controls to report having no formal education (AOR 2.3, 95% CI 1.2-4.2), feeling ashamed to have TB (AOR 2.0, 95% CI 1.3-3.0), not receiving adequate counseling about their treatment (AOR 1.9, 95% CI 1.2-2.8), drinking any alcohol during TB treatment (AOR 1.9, 95% CI 1.2-3.0), and seeing a traditional healer during TB treatment (AOR 1.9, 95% CI 1.1-3.4). Among re-treatment patients, risk factors included stopping TB treatment because they felt better (AOR 21, 95% CI 5.2-84), having a previous history of TB treatment default (AOR 6.4, 95% CI 2.9-14), and feeling that food provisions might have helped them finish treatment (AOR 5.0, 95% CI 1.3-19).

CONCLUSIONS

Risk factors for default differ between new and re-treatment TB patients in South Africa. Addressing default in both populations with targeted interventions is critical to overall program success.

WHO guidelines for the programmatic management of drug-resistant tuberculosis: 2011 update

The production of guidelines for the management of drug-resistant tuberculosis (TB) fits the mandate of the World Health Organization (WHO) to support countries in the reinforcement of patient care. WHO commissioned external reviews to summarise evidence on priority questions regarding case-finding, treatment regimens for multidrug-resistant TB (MDR-TB), monitoring the response to MDR-TB treatment, and models of care. A multidisciplinary expert panel used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to develop recommendations. The recommendations support the wider use of rapid drug susceptibility testing for isoniazid and rifampicin or rifampicin alone using molecular techniques. Monitoring by sputum culture is important for early detection of failure during treatment. Regimens lasting ≥ 20 months and containing pyrazinamide, a fluoroquinolone, a second-line injectable drug, ethionamide (or prothionamide), and either cycloserine or p-aminosalicylic acid are recommended. The guidelines promote the early use of antiretroviral agents for TB patients with HIV on second-line drug regimens. Systems that primarily employ ambulatory models of care are recommended over others based mainly on hospitalisation. Scientific and medical associations should promote the recommendations among practitioners and public health decision makers involved in MDR-TB care. Controlled trials are needed to improve the quality of existing evidence, particularly on the optimal composition and duration of MDR-TB treatment regimens.

Outcomes of multi-drug resistant tuberculosis (MDR-TB) among a cohort of South African patients with high HIV prevalence

BACKGROUND

Multidrug-resistant tuberculosis (MDR-TB) is a major clinical challenge, particularly in patients with human immunodeficiency virus (HIV) co-infection. MDR-TB treatment is increasingly available, but outcomes have not been well characterized. South Africa has provided MDR-TB treatment for a decade, and we evaluated outcomes by HIV status for patients enrolled between 2000 and 2004 prior to anti-retroviral access.

METHODS

We assessed treatment outcomes in a prospective cohort of patients with MDR-TB from eight provincial programs providing second line drugs. World Health Organization definitions were used. Results were stratified by HIV status.

RESULTS

Seven hundred fifty seven patients with known HIV status were included in the final analysis, and HIV infection was documented in 287 (38%). Overall, 348 patients (46.0%) were successfully treated, 74 (9.8%) failed therapy, 177 (23.4%) died and 158 (20.9%) defaulted. Patients with HIV were slightly younger and less likely to be male compared to HIV negative patients. Patients with HIV were less likely to have a successful treatment outcome (40.0 vs. 49.6; P<0.05) and more likely to die (35.2 vs. 16.2; P<0.0001). In a competing risk survival analysis, patients with HIV had a higher hazard of death (HR: 2.33, P<0.0001). Low baseline weight (less than 45 kg and less than 60 kg) was also associated with a higher hazard of death (HR: 2.52, P<0.0001; and HR: 1.50, P<0.0001, respectively, compared to weight greater than 60 kg). Weight less than 45 kg had higher risk of failure (HR: 3.58, P<0.01). Any change in treatment regimen was associated with a higher hazard of default (HR: 2.86; 95% CI 1.55-5.29, P<0.001) and a lower hazard of death (HR: 0.63, P<0.05).

CONCLUSIONS

In this MDR-TB treatment program patients with HIV infection and low weight had higher hazards of death. Overall treatment outcomes were poor. Efforts to improve treatment for MDR-TB are urgently needed.