Scaling up Xpert MTB/RIF technology: the costs of laboratory- vs. clinic-based roll-out in South Africa

The Value-of-Information and Value-of-Implementation from Clinical Trials of Diagnostic Tests for HIV-Associated Tuberculosis: A Modeling Analysis

Objectives. Conventional value-of-information (VOI) analysis assumes complete uptake of an optimal decision. We employed an extended framework that includes value-of-implementation (VOM)-the benefit of encouraging adoption of an optimal strategy-and estimated how future trials of diagnostic tests for HIV-associated tuberculosis could improve public health decision making and clinical and economic outcomes. Methods. We evaluated the clinical outcomes and costs, given current information, of 3 tuberculosis screening strategies among hospitalized people with HIV in South Africa: sputum Xpert (Xpert), sputum Xpert plus urine AlereLAM (Xpert+AlereLAM), and sputum Xpert plus the newer, more sensitive, and costlier urine FujiLAM (Xpert+FujiLAM). We projected the incremental net monetary benefit (INMB) of decision making based on results of a trial comparing mortality with each strategy, rather than decision making based solely on current knowledge of FujiLAM's improved diagnostic performance. We used a validated microsimulation to estimate VOI (the INMB of reducing parameter uncertainty before decision making) and VOM (the INMB of encouraging adoption of an optimal strategy). Results. With current information, adopting Xpert+FujiLAM yields 0.4 additional life-years/person compared with current practices (assumed 50% Xpert and 50% Xpert+AlereLAM). While the decision to adopt this optimal strategy is unaffected by information from the clinical trial (VOI = $ 0 at $3,000/year-of-life saved willingness-to-pay threshold), there is value in scaling up implementation of Xpert+FujiLAM, which results in an INMB (representing VOM) of $650 million over 5 y. Conclusions. Conventional VOI methods account for the value of switching to a new optimal strategy based on trial data but fail to account for the persuasive value of trials in increasing uptake of the optimal strategy. Evaluation of trials should include a focus on their value in reducing barriers to implementation.

Highlights

In conventional VOI analysis, it is assumed that the optimal decision will always be adopted even without a trial. This can potentially lead to an underestimation of the value of trials when adoption requires new clinical trial evidence. To capture the influence that a trial may have on decision makers' willingness to adopt the optimal decision, we also consider value-of-implementation (VOM), a metric quantifying the benefit of new study information in promoting wider adoption of the optimal strategy. The overall value-of-a-trial (VOT) includes both VOI and VOM.Our model-based analysis suggests that the information obtained from a trial of screening strategies for HIV-associated tuberculosis in South Africa would have no value, when measured using traditional methods of VOI assessment. A novel strategy, which includes the urine FujiLAM test, is optimal from a health economic standpoint but is underutilized. A trial would reduce uncertainties around downstream health outcomes but likely would not change the optimal decision. The high VOT (nearly $700 million over 5 y) lies solely in promoting uptake of FujiLAM, represented as VOM.Our results highlight the importance of employing a more comprehensive approach for evaluating prospective trials, as conventional VOI methods can vastly underestimate their value. Trialists and funders can and should assess the VOT metric instead when considering trial designs and costs. If VOI is low, the VOM and cost of a trial can be compared with the benefits and costs of other outreach programs to determine the most cost-effective way to improve uptake.

Cost-effectiveness of GeneXpert Omni compared with GeneXpert MTB/Rif for point-of-care diagnosis of tuberculosis in a low-resource, high-burden setting in Eastern Uganda: a cost-effectiveness analysis based on decision analytical modelling

OBJECTIVE

To determine the cost-effectiveness of Xpert Omni compared with Xpert MTB/Rif for point-of-care diagnosis of tuberculosis among presumptive cases in a low-resource, high burden facility.

DESIGN

Cost-effectiveness analysis from the provider's perspective.

SETTING

A low-resource, high tuberculosis burden district in Eastern Uganda.

PARTICIPANTS

A provider's perspective was used, and thus, data were collected from experts in the field of tuberculosis diagnosis purposively selected at the local, subnational and national levels.

METHODS

A decision analysis model was contracted from TreeAge comparing Xpert MTB/Rif and Xpert Omni. Cost estimation was done using the ingredients' approach. One-way deterministic sensitivity analyses were performed to identify the most influential model parameters.

OUTCOME MEASURE

The outcome measure was incremental cost per additional test diagnosed expressed as the incremental cost-effectiveness ratio.

RESULTS

The total cost per test for Xpert MTB/Rif was US$14.933. Cartridge and reagent kits contributed to 67% of Xpert MTB/Rif costs. Sample transport costs increased the cost per test of Xpert MTB/Rif by $1.28. The total cost per test for Xpert Omni was $16.153. Cartridge and reagent kits contributed to over 71.2% of Xpert Omni's cost per test. The incremental cost-effectiveness ratio for using Xpert Omni as a replacement for Xpert MTB/Rif was US$30.73 per additional case detected. There was no dominance noted in the cost-effectiveness analysis, meaning no strategy was dominant over the other.

CONCLUSION

The use of Xpert Omni at the point-of-care health facility was more effective but with an increased cost compared with Xpert MTB/Rif at the centralised referral testing facility.

Bridging the Gap Between Pilot and Scale-Up: A Model of Antenatal Testing for Curable Sexually Transmitted Infections From Botswana

BACKGROUND

Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are common sexually transmitted infections (STIs) associated with adverse outcomes, yet most countries do not test and conduct syndromic management, which lacks sensitivity and specificity. Innovations allow for expanded STI testing; however, cost is a barrier.

METHODS

Using inputs from a pilot program in Botswana, we developed a model among a hypothetical population of 50,000 pregnant women to compare 1-year costs and outcomes associated with 3 antenatal STI testing strategies: (1) point-of-care, (2) centralized laboratory, and (3) a mixed approach (point of care at high-volume sites, and hubs elsewhere), and syndromic management.

RESULTS

Syndromic management had the lowest delivery cost but was associated with the most infections at delivery, uninfected women treated, CT/NG-related low-birth-weight infants, disability-adjusted life years, and low birth weight hospitalization costs. Point-of-care CT/NG testing would treat and cure the most infections but had the highest delivery cost. Among the testing scenarios, the mixed scenario had the most favorable cost per woman treated and cured ($534/cure). Compared with syndromic management, the mixed approach resulted in a mean incremental cost-effectiveness ratio of $953 per disability-adjusted life years averted, which is cost-effective under World Health Organization's one-time per-capita gross domestic product willingness-to-pay threshold.

CONCLUSIONS

As countries consider new technologies to strengthen health services, there is an opportunity to determine how to best deploy resources. Compared with point-of-care, centralized laboratory, and syndromic management, the mixed approach offered the lowest cost per infection averted and is cost-effective if policy makers' willingness to pay is informed by the World Health Organization's gross domestic product/capita threshold.

Establishing the cost of Xpert MTB/RIF mobile testing in high-burden peri-mining communities in South Africa

Background

Globally, tuberculosis remains a major cause of mortality, with an estimated 1.3 million deaths per annum. The Xpert MTB/RIF assay is used as the initial diagnostic test in the tuberculosis diagnostic algorithm. To extend the national tuberculosis testing programme in South Africa, mobile units fitted with the GeneXpert equipment were introduced to high-burden peri-mining communities.

Objective

This study sought to assess the cost of mobile testing compared to traditional laboratory-based testing in a peri-mining community setting.

Methods

Actual cost data for mobile and laboratory-based Xpert MTB/RIF testing from 2018 were analysed using a bottom-up ingredients-based approach to establish the annual equivalent cost and the cost per result. Historical cost data were obtained from supplier quotations and the local enterprise resource planning system. Costs were obtained in rand and reported in United States dollars (USD).

Results

The mobile units performed 4866 tests with an overall cost per result of $49.16. Staffing accounted for 30.7% of this cost, while reagents and laboratory equipment accounted for 20.7% and 20.8%. The cost per result of traditional laboratory-based testing was $15.44 US dollars (USD). The cost for identifying a tuberculosis-positive result using mobile testing was $439.58 USD per case, compared to $164.95 USD with laboratory-based testing.

Conclusion

Mobile testing is substantially more expensive than traditional laboratory services but offers benefits for rapid tuberculosis case detection and same-day antiretroviral therapy initiation. Mobile tuberculosis testing should however be reserved for high-burden communities with limited access to laboratory testing where immediate intervention can benefit patient outcomes.

Point-of-care viral load testing among adolescents and youth living with HIV in Haiti: a protocol for a randomised trial to evaluate implementation and effect

INTRODUCTION

Adolescents living with HIV have poor antiretroviral therapy (ART) adherence and viral suppression outcomes. Viral load (VL) monitoring could reinforce adherence but standard VL testing requires strong laboratory capacity often only available in large central laboratories. Thus, coordinated transport of samples and results between the clinic and laboratory is required, presenting opportunities for delayed or misplaced results. Newly available point-of-care (POC) VL testing systems return test results the same day and could simplify VL monitoring so that adolescents receive test results faster which could strengthen adherence counselling and improve ART adherence and viral suppression.

METHODS AND ANALYSIS

This non-blinded randomised clinical trial is designed to evaluate the implementation and effectiveness of POC VL testing compared with standard laboratory-based VL testing among adolescents and youth living with HIV in Haiti. A total of 150 participants ages 10-24 who have been on ART for >6 months are randomised 1:1 to intervention or standard arms. Intervention arm participants receive a POC VL test (Cepheid Xpert HIV-1 Viral Load system) with same-day result and immediate ART adherence counselling. Standard care participants receive a laboratory-based VL test (Abbott m2000sp/m2000rt) with the result available 1 month later, at which time they receive ART adherence counselling. VL testing is repeated 6 months later for both arms. The primary objective is to describe the implementation of POC VL testing compared with standard laboratory-based VL testing. The secondary objective is to evaluate the effect of POC VL testing on VL suppression at 6 months and participant comprehension of the correlation between VL and ART adherence.

ETHICS AND DISSEMINATION

This study is approved by GHESKIO, Weill Cornell Medicine and Columbia University ethics committees. This trial will provide critical data to understand if and how POC VL testing may impact adolescent ART adherence and viral suppression. If effective, POC VL testing could routinely supplement standard laboratory-based VL testing among high-risk populations living with HIV.

TRIAL REGISTRATION NUMBER

NCT03288246.

A Systematic Review of Methodological Variation in Healthcare Provider Perspective Tuberculosis Costing Papers Conducted in Low- and Middle-Income Settings, Using An Intervention-Standardised Unit Cost Typology

BACKGROUND

There is a need for easily accessible tuberculosis unit cost data, as well as an understanding of the variability of methods used and reporting standards of that data.

OBJECTIVE

The aim of this systematic review was to descriptively review papers reporting tuberculosis unit costs from a healthcare provider perspective looking at methodological variation; to assess quality using a study quality rating system and machine learning to investigate the indicators of reporting quality; and to identify the data gaps to inform standardised tuberculosis unit cost collection and consistent principles for reporting going forward.

METHODS

We searched grey and published literature in five sources and eight databases, respectively, using search terms linked to cost, tuberculosis and tuberculosis health services including tuberculosis treatment and prevention. For inclusion, the papers needed to contain empirical unit cost estimates for tuberculosis interventions from low- and middle-income countries, with reference years between 1990 and 2018. A total of 21,691 papers were found and screened in a phased manner. Data were extracted from the eligible papers into a detailed Microsoft Excel tool, extensively cleaned and analysed with R software (R Project, Vienna, Austria) using the user interface of RStudio. A study quality rating was applied to the reviewed papers based on the inclusion or omission of a selection of variables and their relative importance. Following this, machine learning using a recursive partitioning method was utilised to construct a classification tree to assess the reporting quality.

RESULTS

This systematic review included 103 provider perspective papers with 627 unit costs (costs not presented here) for tuberculosis interventions among a total of 140 variables. The interventions covered were active, passive and intensified case finding; tuberculosis treatment; above-service costs; and tuberculosis prevention. Passive case finding is the detection of tuberculosis cases where individuals self-identify at health facilities; active case finding is detection of cases of those not in health facilities, such as through outreach; and intensified case finding is detection of cases in high-risk populations. There was heterogeneity in some of the reported methods used such cost allocation, amortisation and the use of top-down, bottom-up or mixed approaches to the costing. Uncertainty checking through sensitivity analysis was only reported on by half of the papers (54%), while purposive and convenience sampling was reported by 72% of papers. Machine learning indicated that reporting on 'Intervention' (in particular), 'Urbanicity' and 'Site Sampling', were the most likely indicators of quality of reporting. The largest data gap identified was for tuberculosis vaccination cost data, the Bacillus Calmette-Guérin (BCG) vaccine in particular. There is a gap in available unit costs for 12 of 30 high tuberculosis burden countries, as well as for the interventions of above-service costs, tuberculosis prevention, and active and intensified case finding.

CONCLUSION

Variability in the methods and reporting used makes comparison difficult and makes it hard for decision makers to know which unit costs they can trust. The study quality rating system used in this review as well as the classification tree enable focus on specific reporting aspects that should improve variability and increase confidence in unit costs. Researchers should endeavour to be explicit and transparent in how they cost interventions following the principles as laid out in the Global Health Cost Consortium's Reference Case for Estimating the Costs of Global Health Services and Interventions, which in turn will lead to repeatability, comparability and enhanced learning from others.

Point of care Xpert MTB/RIF versus smear microscopy for tuberculosis diagnosis in southern African primary care clinics: a multicentre economic evaluation

BACKGROUND

Rapid on-site diagnosis facilitates tuberculosis control. Performing Xpert MTB/RIF (Xpert) at point of care is feasible, even when performed by minimally trained health-care workers, and when compared with point-of-care smear microscopy, reduces time to diagnosis and pretreatment loss to follow-up. However, whether Xpert is cost-effective at point of care remains unclear.

METHODS

We empirically collected cost (US$, 2014) and clinical outcome data from participants presenting to primary health-care facilities in four African countries (South Africa, Zambia, Zimbabwe, and Tanzania) during the TB-NEAT trial. Costs were determined using an bottom-up ingredients approach. Effectiveness measures from the trial included number of cases diagnosed, initiated on treatment, and completing treatment. The primary outcome was the incremental cost-effectiveness of point-of-care Xpert relative to smear microscopy. The study was performed from the perspective of the health-care provider.

FINDINGS

Using data from 1502 patients, we calculated that the mean Xpert unit cost was lower when performed at a centralised laboratory (Lab Xpert) rather than at point of care ($23·00 [95% CI 22·12-23·88] vs $28·03 [26·19-29·87]). Per 1000 patients screened, and relative to smear microscopy, point-of-care Xpert cost an additional $35 529 (27 054-40 025) and was associated with an additional 24·3 treatment initiations ([-20·0 to 68·5]; $1464 per treatment), 63·4 same-day treatment initiations ([27·3-99·4]; $511 per same-day treatment), and 29·4 treatment completions ([-6·9 to 65·6]; $1211 per completion). Xpert costs were most sensitive to test volume, whereas incremental outcomes were most sensitive to the number of patients initiating and completing treatment. The probability of point-of-care Xpert being cost-effective was 90% at a willingness to pay of $3820 per treatment completion.

INTERPRETATION

In southern Africa, although point-of-care Xpert unit cost is higher than Lab Xpert, it is likely to offer good value for money relative to smear microscopy. With the current availability of point-of-care nucleic acid amplification platforms (eg, Xpert Edge), these data inform much needed investment and resource allocation strategies in tuberculosis endemic settings.

FUNDING

European Union European and Developing Countries Clinical Trials Partnership.

A review of microsampling techniques and their social impact

Conventional skin and blood sampling techniques for disease diagnosis, though effective, are often highly invasive and some even suffer from variations in analysis. With the improvements in molecular detection, the amount of starting sample quantity needed has significantly reduced in some diagnostic procedures, and this has led to an increased interest in microsampling techniques for disease biomarker detection. The miniaturization of sampling platforms driven by microsampling has the potential to shift disease diagnosis and monitoring closer to the point of care. The faster turnaround time for actionable results has improved patient care. The variations in sample quantification and analysis remain a challenge in the microsampling field. The future of microsampling looks promising. Emerging techniques are being clinically tested and monitored by regulatory bodies. This process is leading to safer and more reliable diagnostic platforms. This review discusses the advantages and disadvantages of current skin and blood microsampling techniques.

Rapid, point-of-care diagnosis of tuberculosis with novel Truenat assay: Cost-effectiveness analysis for India's public sector

Background

Truenat is a novel molecular assay that rapidly detects tuberculosis (TB) and rifampicin-resistance. Due to the portability of its battery-powered testing platform, it may be valuable in peripheral healthcare settings in India.

Methods

Using a microsimulation model, we compared four TB diagnostic strategies for HIV-negative adults with presumptive TB: (1) sputum smear microscopy in designated microscopy centers (DMCs) (SSM); (2) Xpert MTB/RIF in DMCs (Xpert); (3) Truenat in DMCs (Truenat DMC); and (4) Truenat for point-of-care testing in primary healthcare facilities (Truenat POC). We projected life expectancy, costs, incremental cost-effectiveness ratios (ICERs), and 5-year budget impact of deploying Truenat POC in India’s public sector. We defined a strategy “cost-effective” if its ICER was <US$990/year-of-life saved (YLS). Model inputs included: TB prevalence, 15% (among those not previously treated for TB) and 27% (among those previously treated for TB); sensitivity for TB detection, 89% (Xpert) and 86% (Truenat); per test cost, $12.63 (Xpert) and $13.20 (Truenat); and linkage-to-care after diagnosis, 84% (DMC) and 95% (POC). We varied these parameters in sensitivity analyses.

Results

Compared to SSM, Truenat POC increased life expectancy by 0.39 years and was cost-effective (ICER $210/YLS). Compared to Xpert, Truenat POC increased life expectancy by 0.08 years due to improved linkage-to-care and was cost-effective (ICER $120/YLS). In sensitivity analysis, the cost-effectiveness of Truenat POC, relative to Xpert, depended on the diagnostic sensitivity of Truenat and linkage-to-care with Truenat. Deploying Truenat POC instead of Xpert increased 5-year expenditures by $270 million, due mostly to treatment costs. Limitations of our study include uncertainty in Truenat’s sensitivity for TB and not accounting for the “start-up” costs of implementing Truenat in the field.

Conclusions

Used at the point-of-care in India, Truenat for TB diagnosis should improve linkage-to-care, increase life expectancy, and be cost-effective compared with smear microscopy or Xpert.

Time-and-motion tool for the assessment of working time in tuberculosis laboratories: a multicentre study

SETTING

Implementation of novel diagnostic assays in tuberculosis (TB) laboratory diagnosis requires effective management of time and resources.

OBJECTIVE

To further develop and assess at multiple centres a time-and-motion (T&M) tool as an objective means for recording the actual time spent on running laboratory assays.

DESIGN

Multicentre prospective study conducted in six European Union (EU) reference TB laboratories.

RESULTS

A total of 1060 specimens were tested using four laboratory assays. The number of specimens per batch varied from one to 60; a total of 64 recordings were performed. Theoretical hands-on times per specimen (TTPS) in h:min:s for Xpert® MTB/RIF, mycobacterial interspersed repetitive unit-variable number of tandem repeats genotyping, Ziehl-Neelsen staining and manual fluorescence microscopy were respectively 00:33:02 ± 00:12:32, 00:13:34 ± 00:03:11, 00:09:54 ± 00:00:53 and 00:06:23 ± 00:01:36. Variations between laboratories were predominantly linked to the time spent on reporting and administrative procedures. Processing specimens in batches could help save time in highly automated assays (e.g., line-probe) (TTPS 00:14:00 vs. 00:09:45 for batches comprising 7 and 31 specimens, respectively).

CONCLUSIONS

The T&M tool can be considered a universal and objective methodology contributing to workload assessment in TB diagnostic laboratories. Comparison of workload between laboratories could help laboratory managers justify their resource and personnel needs for the implementation of novel, time-saving, cost-effective technologies, as well as identify areas for improvement.

Lessons on the quality of tuberculosis diagnosis from standardized patients in China, India, Kenya, and South Africa

Standardized patients (SPs) are people who are recruited locally, trained to make identical scripted clinical presentations, deployed incognito to multiple different health care providers, and debriefed using a structured reporting instrument. The use of SPs has increased dramatically as a method for assessing quality of TB care since it was first validated and used for tuberculosis in 2015. This paper summarizes common findings using 3,086 SP-provider interactions involving tuberculosis across various sampling strata in published studies from India, China, South Africa and Kenya. It then discusses the lessons learned from implementing standardized patients in these diverse settings. First, quality is low: relatively few SPs presenting to a health care provider for the first time were given an appropriate diagnostic test, and most were given unnecessary or inappropriate medication. Second, care takes a wide variety of forms – SPs did not generally receive “wait and see” or “symptomatic” care from providers, but they received a medley of care patterns that included broad-spectrum antibiotics as well as contraindicated quinolone antibiotics and steroids. Third, there is a wide range of estimated quality in each observed sampling stratum: more-qualified providers and higher-level facilities performed better than others in all settings, but in every stratum there were both high- and low-quality providers. Evidence from SP studies paired with medical vignettes has shown that providers of all knowledge levels significantly underperform their demonstrated ability with real patients. Finally, providers showed little response to differences in patient identity, but showed strong responses to differences in case presentation that give some clues as to the reasons for these behaviors.

Cost Analysis of Tuberculosis Diagnosis in Cambodia with and without Xpert® MTB/RIF for People Living with HIV/AIDS and People with Presumptive Multidrug-resistant Tuberculosis

BACKGROUND

The Xpert^® MTB/RIF (Xpert) test has been shown to be effective and cost-effective for diagnosing tuberculosis (TB) under conditions with high HIV prevalence and HIV-TB co-infection but less is known about Xpert's cost in low HIV prevalence settings. Cambodia, a country with low HIV prevalence (0.7%), high TB burden, and low multidrug-resistant (MDR) TB burden (1.4% of new TB cases, 11% of retreatment cases) introduced Xpert into its TB diagnostic algorithms for people living with HIV (PLHIV) and people with presumptive MDR TB in 2012. The study objective was to estimate these algorithms' costs pre- and post-Xpert introduction in four provinces of Cambodia.

METHODS

Using a retrospective, ingredients-based microcosting approach, primary cost data on personnel, equipment, maintenance, supplies, and specimen transport were collected at four sites through observation, records review, and key informant consultations.

RESULTS

Across the sample facilities, the cost per Xpert test was US$33.88-US$37.11, clinical exam cost US$1.22-US$1.84, chest X-ray cost US$2.02-US$2.14, fluorescent microscopy (FM) smear cost US$1.56-US$1.93, Ziehl-Neelsen (ZN) smear cost US$1.26, liquid culture test cost US$11.63-US$22.83, follow-on work-up for positive culture results and Mycobacterium tuberculosis complex (MTB) identification cost US$11.50-US$14.72, and drug susceptibility testing (DST) cost US$44.26. Specimen transport added US$1.39-US$5.21 per sample. Assuming clinician adherence to the algorithms and perfect test accuracy, the normative cost per patient correctly diagnosed under the post-Xpert algorithms would be US$25-US$29 more per PLHIV and US$34-US$37 more per person with presumptive MDR TB (US$41 more per PLHIV when accounting for variable test sensitivity and specificity).

CONCLUSIONS

Xpert test unit costs could be reduced through lower cartridge prices, longer usable life of GeneXpert^® (Cepheid, USA) instruments, and increased test volumes; however, epidemiological and test eligibility conditions in Cambodia limit the number of specimens received at laboratories, leading to sub-optimal utilization of current instruments. Improvements to patient referral and specimen transport could increase test volumes and reduce Xpert test unit costs in this setting.

Incremental cost-effectiveness of the second Xpert MTB/RIF assay to detect Mycobacterium tuberculosis

Background

Due to the non-homogeneity of specimens collected from tuberculosis (TB) suspects, repeated Xpert MTB/RIF (Xpert) may have potential clinical benefits. Incremental cost-effectiveness was analyzed for the second Xpert assay to detect Mycobacterium tuberculosis (Mtb) and rifampicin (RIF) resistance.

Methods

Specimens were collected from 1,063 pulmonary TB (PTB) and 398 extrapulmonary TB (EPTB) suspects, who had two Xpert tests sequentially within one week. The specimens were subjected to smear, culture, Xpert and drug susceptibility testing. Incremental cost-effectiveness of the serial Xpert assays was evaluated.

Results

Among 813 Xpert-positive TB patients, 755 (92.87%) were identified by the first assay whereas the additional 58 (7.13%) were identified by the second assay. The second Xpert assay had higher incremental yield for smear-negative than for smear-positive specimens (12.07% vs. 1.84%, P<0.001), and higher incremental yield for EPTB than for PTB (10.71% vs. 4.65%, P=0.003). About 94.48% (137/145) of the RIF-resistant patients were identified by the first Xpert assay and 5.52% (8/145) were identified by the second Xpert assay. After the first assay, the incremental cost of performing a second Xpert was huge: US$22.82 vs. US$467.72 (P<0.001) and US$35.02 vs. US$291.87 (P<0.001) for PTB and EPTB, respectively. The incremental cost of performing a second Xpert is lower in smear-negative than in smear-positive group in both PTB and EPTB.

Conclusions

One Xpert assay is sufficient for smear-positive cases, and a second Xpert assay is beneficial not only for Mtb detection but also for RIF-resistant diagnosis for smear-negative TB suspects, whereas the incremental cost for the second Xpert is huge.

Higher cost of implementing Xpert(®) MTB/RIF in Ugandan peripheral settings: implications for cost-effectiveness

SETTING

Initial cost-effectiveness evaluations of Xpert(®) MTB/RIF for tuberculosis (TB) diagnosis have not fully accounted for the realities of implementation in peripheral settings.

OBJECTIVE

To evaluate costs and diagnostic outcomes of Xpert testing implemented at various health care levels in Uganda.

DESIGN

We collected empirical cost data from five health centers utilizing Xpert for TB diagnosis, using an ingredients approach. We reviewed laboratory and patient records to assess outcomes at these sites and10 sites without Xpert. We also estimated incremental cost-effectiveness of Xpert testing; our primary outcome was the incremental cost of Xpert testing per newly detected TB case.

RESULTS

The mean unit cost of an Xpert test was US$21 based on a mean monthly volume of 54 tests per site, although unit cost varied widely (US$16-58) and was primarily determined by testing volume. Total diagnostic costs were 2.4-fold higher in Xpert clinics than in non-Xpert clinics; however, Xpert only increased diagnoses by 12%. The diagnostic costs of Xpert averaged US$119 per newly detected TB case, but were as high as US$885 at the center with the lowest volume of tests.

CONCLUSION

Xpert testing can detect TB cases at reasonable cost, but may double diagnostic budgets for relatively small gains, with cost-effectiveness deteriorating with lower testing volumes.

Point-of-care diagnostics to improve maternal and neonatal health in low-resource settings

Each day, approximately 830 women and 7400 newborns die from complications during pregnancy and childbirth. Improving maternal and neonatal health will require bringing rapid diagnosis and treatment to the point of care in low-resource settings. However, to date there are few diagnostic tools available that can be used at the point of care to detect the leading causes of maternal and neonatal mortality in low-resource settings. Here we review both commercially available diagnostics and technologies that are currently in development to detect the leading causes of maternal and neonatal mortality, highlighting key gaps in development where innovative design could increase access to technology and enable rapid diagnosis at the bedside.

Impact of Point-of-Care Xpert MTB/RIF on Tuberculosis Treatment Initiation. A Cluster-randomized Trial

RATIONALE

Point-of-care (POC) diagnostics have the potential to reduce pretreatment loss to follow-up and delays to initiation of appropriate tuberculosis (TB) treatment.

OBJECTIVES

To evaluate the effect of a POC diagnostic strategy on initiation of appropriate TB treatment.

METHODS

We conducted a cluster-randomized trial of adults with cough who were HIV positive and/or at high risk of drug-resistant TB. Two-week time blocks were randomized to two strategies: (1) Xpert MTB/RIF test (Cepheid, Sunnyvale, CA) performed at a district hospital laboratory or (2) POC Xpert MTB/RIF test performed at a primary health care clinic. All participants provided two sputum specimens: one for the Xpert test and the other for culture as a reference standard. The primary outcome was the proportion of participants with culture-positive pulmonary tuberculosis (PTB) initiated on appropriate TB treatment within 30 days.

MEASUREMENTS AND MAIN RESULTS

Between August 22, 2011, and March 1, 2013, 36 two-week blocks were randomized, and 1,297 individuals were enrolled (646 in the laboratory arm, 651 in the POC arm), 159 (12.4%) of whom had culture-positive PTB. The proportions of participants with culture-positive PTB initiated on appropriate TB treatment within 30 days were 76.5% in the laboratory arm and 79.5% in the POC arm (odds ratio, 1.13; 95% confidence interval, 0.51-2.53; P = 0.76; risk difference, 3.1%; 95% confidence interval, -16.2 to 10.1). The median time to initiation of appropriate treatment was 7 days (laboratory) versus 1 day (POC).

CONCLUSIONS

POC positioning of the Xpert test led to more rapid initiation of appropriate TB treatment. Achieving one-stop diagnosis and treatment for all people with TB will require simpler, more sensitive diagnostics and broader strengthening of health systems. Clinical trial registered with www.isrctn.com (ISRCTN 18642314) and www.sanctr.gov.za (DOH-27-0711-3568).

Xpert® MTB/RIF: Usefulness for the diagnosis of tuberculosis and resistance to rifampicin

The advent of the Xpert® MTB/RIF technique was a revolution in the diagnosis of tuberculosis, especially in areas with high incidence and low resources. It allows the detection of Mycobacterium tuberculosis complex and simultaneously the most common resistance mutations to rifampicin in less than 2h. For respiratory samples the sensitivity is very high, but it decreases for extrapulmonary samples and children. Although it is faster and simpler than conventional methods, it presents some limitations and new and better techniques are needed to reduce the number of cases and deaths caused by tuberculosis. This review aims to assess the scientific evidence around the diagnostic performance of Xpert® MTB/RIF in different types of samples and populations, as well as analyse its strengths and limitations for TB diagnosis.

Microscopic observation drug-susceptibility assay vs. Xpert® MTB/RIF for the diagnosis of tuberculosis in a rural African setting: a cost-utility analysis

OBJECTIVE

To compare the cost-utility of microscopic observation drug-susceptibility assay (MODS) and Xpert^® MTB/RIF implementation for tuberculosis (TB) diagnosis in rural northern Mozambique.

METHODS

Stochastic transmission compartmental TB model from the healthcare provider perspective with parameter input from direct measurements, systematic literature reviews and expert opinion. MODS and Xpert^® MTB/RIF were evaluated as replacement test of smear microscopy (SM) or as an add-on test after a negative SM. Costs were calculated in 2013 USD, effects in disability-adjusted life years (DALY). Willingness to pay threshold (WPT) was established at once the per capita Gross National Income of Mozambique.

RESULTS

MODS as an add-on test to negative SM produced an incremental cost-effectiveness ratio (ICER) of 5647.89USD/DALY averted. MODS as a substitute for SM yielded an ICER of 5374.58USD/DALY averted. Xpert^® MTB/RIF as an add-on test to negative SM yielded ICER of 345.71USD/DALY averted. Xpert^® MTB/RIF as a substitute for SM obtained an ICER of 122.13USD/DALY averted. TB prevalence and risk of infection were the main factors impacting MODS and Xpert^® MTB/RIF ICER in the one-way sensitivity analysis. In the probabilistic sensitivity analysis, Xpert^® MTB/RIF was most likely to have an ICER below the WPT, whereas MODS was not.

CONCLUSION

Our cost-utility analysis favours the implementation of Xpert^® MTB/RIF as a replacement of SM for all TB suspects in this rural high TB/HIV prevalence African setting.

The laboratory health system and its response to the Ebola virus disease outbreak in Liberia

The laboratory system in Liberia has generally been fragmented and uncoordinated. Accordingly, the country's Ministry of Health established the National Reference Laboratory to strengthen and sustain laboratory services. However, diagnostic testing services were often limited to clinical tests performed in health facilities, with the functionality of the National Reference Laboratory restricted to performing testing services for a limited number of epidemic-prone diseases. The lack of testing capacity in-country for Lassa fever and other haemorrhagic fevers affected the response of the country's health system during the onset of the Ebola virus disease (EVD) outbreak. Based on the experiences of the EVD outbreak, efforts were initiated to strengthen the laboratory system and infrastructure, enhance human resource capacity, and invest in diagnostic services and public health surveillance to inform admittance, treatment, and discharge decisions. In this article, we briefly describe the pre-EVD laboratory capability in Liberia, and extensively explore the post-EVD strengthening initiatives to enhance capacity, mobilise resources and coordinate disaster response with international partners to rebuild the laboratory infrastructure in the country. Now that the EVD outbreak has ended, additional initiatives are needed to revise the laboratory strategic and operational plan for post-EVD relevance, promote continual human resource capacity, institute accreditation and validation programmes, and coordinate the investment strategy to strengthen and sustain the preparedness of the laboratory sector to mitigate future emerging and re-emerging infectious diseases.

Cost-effectiveness analysis of microscopic observation drug susceptibility test versus Xpert MTB/Rif test for diagnosis of pulmonary tuberculosis in HIV patients in Uganda

BACKGROUND

Microscopic Observation Drug Susceptibility (MODS) and Xpert MTB/Rif (Xpert) are highly sensitive tests for diagnosis of pulmonary tuberculosis (PTB). This study evaluated the cost effectiveness of utilizing MODS versus Xpert for diagnosis of active pulmonary TB in HIV infected patients in Uganda.

METHODS

A decision analysis model comparing MODS versus Xpert for TB diagnosis was used. Costs were estimated by measuring and valuing relevant resources required to perform the MODS and Xpert tests. Diagnostic accuracy data of the tests were obtained from systematic reviews involving HIV infected patients. We calculated base values for unit costs and varied several assumptions to obtain the range estimates. Cost effectiveness was expressed as costs per TB patient diagnosed for each of the two diagnostic strategies. Base case analysis was performed using the base estimates for unit cost and diagnostic accuracy of the tests. Sensitivity analysis was performed using a range of value estimates for resources, prevalence, number of tests and diagnostic accuracy.

RESULTS

The unit cost of MODS was US$ 6.53 versus US$ 12.41 of Xpert. Consumables accounted for 59 % (US$ 3.84 of 6.53) of the unit cost for MODS and 84 % (US$10.37 of 12.41) of the unit cost for Xpert. The cost effectiveness ratio of the algorithm using MODS was US$ 34 per TB patient diagnosed compared to US$ 71 of the algorithm using Xpert. The algorithm using MODS was more cost-effective compared to the algorithm using Xpert for a wide range of different values of accuracy, cost and TB prevalence. The cost (threshold value), where the algorithm using Xpert was optimal over the algorithm using MODS was US$ 5.92.

CONCLUSIONS

MODS versus Xpert was more cost-effective for the diagnosis of PTB among HIV patients in our setting. Efforts to scale-up MODS therefore need to be explored. However, since other non-economic factors may still favour the use of Xpert, the current cost of the Xpert cartridge still needs to be reduced further by more than half, in order to make it economically competitive with MODS.

Outcomes of a clinical diagnostic algorithm for management of ambulatory smear and Xpert MTB/Rif negative HIV infected patients with presumptive pulmonary TB in Uganda: a prospective study

Introduction

Diagnostic guidelines for Tuberculosis (TB) in HIV infected patients previously relied on microscopy where the value of initial antibiotic treatment for exclusion of pulmonary TB (PTB) was limited. New guidelines rely on the Xpert MTB Rif test (Xpert). However, the value of the antibiotic treatment remains unclear particularly in individuals who are smear-negative and Xpert-negative-given Xpert has only moderate sensitivity for smear-negative PTB. We assessed an algorithm involving initial treatment with antibiotics prior empiric TB treatment in HIV patients with presumptive PTB who were both smear and Xpert negative.

Methods

We performed a prospective study with six month follow-up to establish patient response to a course of broad spectrum antibiotics prior empiric TB treatment between March 2012 and June 2013. We calculated the proportion of patients who responded to the antibiotic treatment and those who did not. We computed the crude and adjusted odds ratios with their 95% confidence intervals, for response to the antibiotic treatment on various patient characteristics. We report treatment outcomes for patients who received broad spectrum antibiotics only or who were initiated empiric TB treatment.

Results

Our cohort comprised 162 smear-negative and Xpert-negative patients, of whom 59% (96 of 162) were female, 81% (131 of 162) were on antiretroviral therapy (ART) for a median of 8.7 months. Overall, 88% (141 of 160) responded to the antibiotic treatment, 8% (12 of 160) got empiric TB treatment and 4% (7 out of 160) were treated for other respiratory disease. The odds of improvement on antibiotics were lower in patients with advanced HIV disease than in patients with early HIV disease. Adjusted odds ratios were significant for HIV clinical stage (AOR; 0.038,) and duration on ART (AOR; 1.038,).

Conclusion

The majority of HIV patients with presumptive PTB with smear-negative and Xpert negative results improved on the antibiotic treatment and did not require empiric TB treatment. Initial antibiotic treatment appeared more successful in patients with less advanced HIV disease. Findings from our study suggest it is useful to initiate HIV infected patients with presumptive PTB having smear and Xpert negative results on an initial course of antibiotic treatment prior empiric TB treatment.

Tuberculosis control in prisons: current situation and research gaps

BACKGROUND

Tuberculosis (TB) in penitentiary services (prisons) is a major challenge to TB control. This review article describes the challenges that prison systems encounter in TB control and provides solutions for the more efficient use of limited resources based on the three pillars of the post-2015 End TB Strategy. This paper also proposes research priorities for TB control in prisons based on current challenges.

METHODS

Articles (published up to 2011) included in a recent systematic review on TB control in prisons were further reviewed. In addition, relevant articles in English (published 1990 to May 2014) were identified by searching keywords in PubMed and Google Scholar. Article bibliographies and conference abstracts were also hand-searched.

RESULTS

Despite being a serious cause of morbidity and mortality among incarcerated populations, many prison systems encounter a variety of challenges that hinder TB control. These include, but are not limited to, insufficient laboratory capacity and diagnostic tools, interrupted supply of medicines, weak integration between civilian and prison TB services, inadequate infection control measures, and low policy priority for prison healthcare.

CONCLUSIONS

Governmental commitment, partnerships, and sustained financing are needed in order to facilitate improvements in TB control in prisons, which will translate to the wider community.

Automated chest-radiography as a triage for Xpert testing in resource-constrained settings: a prospective study of diagnostic accuracy and costs

Molecular tests hold great potential for tuberculosis (TB) diagnosis, but are costly, time consuming, and HIV-infected patients are often sputum scarce. Therefore, alternative approaches are needed. We evaluated automated digital chest radiography (ACR) as a rapid and cheap pre-screen test prior to Xpert MTB/RIF (Xpert). 388 suspected TB subjects underwent chest radiography, Xpert and sputum culture testing. Radiographs were analysed by computer software (CAD4TB) and specialist readers, and abnormality scores were allocated. A triage algorithm was simulated in which subjects with a score above a threshold underwent Xpert. We computed sensitivity, specificity, cost per screened subject (CSS), cost per notified TB case (CNTBC) and throughput for different diagnostic thresholds. 18.3% of subjects had culture positive TB. For Xpert alone, sensitivity was 78.9%, specificity 98.1%, CSS $13.09 and CNTBC $90.70. In a pre-screening setting where 40% of subjects would undergo Xpert, CSS decreased to $6.72 and CNTBC to $54.34, with eight TB cases missed and throughput increased from 45 to 113 patients/day. Specialists, on average, read 57% of radiographs as abnormal, reducing CSS ($8.95) and CNTBC ($64.84). ACR pre-screening could substantially reduce costs, and increase daily throughput with few TB cases missed. These data inform public health policy in resource-constrained settings.

Microscopic observation drug susceptibility assay for the diagnosis of TB and MDR-TB in HIV-infected patients: a systematic review and meta-analysis

The objective of the present study was to assess the diagnostic accuracy of the microscopic observation drug susceptibility (MODS) assay for tuberculosis (TB) diagnosis in HIV-infected patients. MEDLINE, EMBASE, LILACS, the Cochrane Central Register of Controlled Trials, African Index Medicus, ResearchGate, SciELO, and the abstracts of the main conferences on infectious diseases and tropical medicine were searched, and other sources investigated. Only studies including HIV-infected patients evaluating MODS for the diagnosis of TB and using culture-based diagnostic tests as a gold standard were analysed. Summary sensitivity and specificity were calculated with a bivariate model. 3259 citations were found, 29 were selected for full-text review and 10 studies including 3075 samples were finally analysed. Overall diagnostic accuracy of MODS for the diagnosis of TB was a sensitivity of 88.3% (95% CI 86.18-90.2%) and specificity 98.2% (95% CI 97.75-98.55%). For multidrug-resistant (MDR)-TB, sensitivity was 89% (95% CI 66.07-97%) and specificity was 100% (95 CI 94.81-100%). For smear-negative pulmonary TB, a sensitivity of 88.2% (95% CI 86.1-89.9%) and specificity of 98.2% (95% CI 96.8-98.9%) were found. Costs varied between USD 0.72 and 7.31 per sample. Mean time to positivity was 8.24 days. MODS was found to have a good accuracy for the diagnosis of TB and MDR-TB in HIV-infected patients with low cost and fast results.

The hidden costs of installing Xpert machines in a tuberculosis high-burden country: experiences from Nigeria

INTRODUCTION

Since the endorsement of GeneXpert MTB/RIF by the WHO, many countries have embarked on implementing this technology.

OBJECTIVE

We outline the cost of installing GeneXpert in district hospitals in Abuja, Nigeria.

METHODS

We prospectively documented costs related to the installation of GeneXpert at five sites. Costs were collected from receipts received from suppliers and normalized to USD 2012 values.

RESULTS

Costs were often identified after initiating installation for many reasons. Installation varied widely between sites with sufficient space and power supply; sites with insufficient space or power supply and costs not directly associated with site installation. The basic cost for installation was USD 2,621.98 per machine. Sites that required additional space cost close to USD 7,000.00.

CONCLUSION

Space and power requirements have a significant effect on installation costs. Countries need to carefully consider the placement of Xpert machines based on the quality and size of the available infrastructure.

Economic challenges associated with tuberculosis diagnostic development

Tuberculosis remains a global health crisis in part due to underdiagnosis. Technological innovations are needed to improve diagnostic test accuracy and reduce the reliance on expensive laboratory infrastructure. However, there are significant economic challenges impeding the development and implementation of new diagnostics. The aim of this piece is to examine the current state of TB diagnostics, outline the unmet needs for new tests, and detail the economic challenges associated with development of new tests from the perspective of developers, policy makers and implementers.

Cost-effectiveness of Xpert® MTB/RIF for diagnosing pulmonary tuberculosis in the United States

SETTING

Conventional approaches to tuberculosis (TB) diagnosis and resistance testing are slow. The Xpert® MTB/RIF assay is an emerging molecular diagnostic assay for rapid TB diagnosis, offering results within 2 hours. However, the cost-effectiveness of implementing Xpert in settings with low TB prevalence, such as the United States, is unknown.

OBJECTIVE

We evaluated the cost-effectiveness of incorporating Xpert into TB diagnostic algorithms in the United States compared to existing diagnostics.

DESIGN

A decision-analysis model compared current TB diagnostic algorithms in the United States to algorithms incorporating Xpert. Primary outcomes were the costs and quality-adjusted life years (QALYs) accrued with each strategy; cost-effectiveness was represented using incremental cost-effectiveness ratios (ICER).

RESULTS

Xpert testing of a single sputum sample from TB suspects is expected to result in lower total health care costs per patient (US2673) compared to diagnostic algorithms using only sputum microscopy and culture (US2728) and improved health outcomes (6.32 QALYs gained per 1000 TB suspects). Compared to existing molecular assays, implementation of Xpert in the United States would be considered highly cost-effective (ICER US39992 per QALY gained).

CONCLUSION

TB diagnostic algorithms incorporating Xpert in the United States are highly cost-effective.

Xpert® MTB/RIF assay for pulmonary tuberculosis and rifampicin resistance in adults

BACKGROUND

Accurate, rapid detection of tuberculosis (TB) and TB drug resistance is critical for improving patient care and decreasing TB transmission. Xpert® MTB/RIF assay is an automated test that can detect both TB and rifampicin resistance, generally within two hours after starting the test, with minimal hands-on technical time. The World Health Organization (WHO) issued initial recommendations on Xpert® MTB/RIF in early 2011. A Cochrane Review on the diagnostic accuracy of Xpert® MTB/RIF for pulmonary TB and rifampicin resistance was published January 2013. We performed this updated Cochrane Review as part of a WHO process to develop updated guidelines on the use of the test.

OBJECTIVES

To assess the diagnostic accuracy of Xpert® MTB/RIF for pulmonary TB (TB detection), where Xpert® MTB/RIF was used as both an initial test replacing microscopy and an add-on test following a negative smear microscopy result.To assess the diagnostic accuracy of Xpert® MTB/RIF for rifampicin resistance detection, where Xpert® MTB/RIF was used as the initial test replacing culture-based drug susceptibility testing (DST).The populations of interest were adults presumed to have pulmonary, rifampicin-resistant or multidrug-resistant TB (MDR-TB), with or without HIV infection. The settings of interest were intermediate- and peripheral-level laboratories. The latter may be associated with primary health care facilities.

SEARCH METHODS

We searched for publications in any language up to 7 February 2013 in the following databases: Cochrane Infectious Diseases Group Specialized Register; MEDLINE; EMBASE; ISI Web of Knowledge; MEDION; LILACS; BIOSIS; and SCOPUS. We also searched the metaRegister of Controlled Trials (mRCT) and the search portal of the WHO International Clinical Trials Registry Platform to identify ongoing trials.

SELECTION CRITERIA

We included randomized controlled trials, cross-sectional studies, and cohort studies using respiratory specimens that allowed for extraction of data evaluating Xpert® MTB/RIF against the reference standard. We excluded gastric fluid specimens. The reference standard for TB was culture and for rifampicin resistance was phenotypic culture-based DST.

DATA COLLECTION AND ANALYSIS

For each study, two review authors independently extracted data using a standardized form. When possible, we extracted data for subgroups by smear and HIV status. We assessed the quality of studies using QUADAS-2 and carried out meta-analyses to estimate pooled sensitivity and specificity of Xpert® MTB/RIF separately for TB detection and rifampicin resistance detection. For TB detection, we performed the majority of analyses using a bivariate random-effects model and compared the sensitivity of Xpert® MTB/RIF and smear microscopy against culture as reference standard. For rifampicin resistance detection, we undertook univariate meta-analyses for sensitivity and specificity separately to include studies in which no rifampicin resistance was detected.

MAIN RESULTS

We included 27 unique studies (integrating nine new studies) involving 9557 participants. Sixteen studies (59%) were performed in low- or middle-income countries. For all QUADAS-2 domains, most studies were at low risk of bias and low concern regarding applicability.As an initial test replacing smear microscopy, Xpert® MTB/RIF pooled sensitivity was 89% [95% Credible Interval (CrI) 85% to 92%] and pooled specificity 99% (95% CrI 98% to 99%), (22 studies, 8998 participants: 2953 confirmed TB, 6045 non-TB).As an add-on test following a negative smear microscopy result, Xpert®MTB/RIF pooled sensitivity was 67% (95% CrI 60% to 74%) and pooled specificity 99% (95% CrI 98% to 99%; 21 studies, 6950 participants).For smear-positive, culture-positive TB, Xpert® MTB/RIF pooled sensitivity was 98% (95% CrI 97% to 99%; 21 studies, 1936 participants).For people with HIV infection, Xpert® MTB/RIF pooled sensitivity was 79% (95% CrI 70% to 86%; 7 studies, 1789 participants), and for people without HIV infection, it was 86% (95% CrI 76% to 92%; 7 studies, 1470 participants). Comparison with smear microscopy In comparison with smear microscopy, Xpert® MTB/RIF increased TB detection among culture-confirmed cases by 23% (95% CrI 15% to 32%; 21 studies, 8880 participants).For TB detection, if pooled sensitivity estimates for Xpert® MTB/RIF and smear microscopy are applied to a hypothetical cohort of 1000 patients where 10% of those with symptoms have TB, Xpert® MTB/RIF will diagnose 88 cases and miss 12 cases, whereas sputum microscopy will diagnose 65 cases and miss 35 cases. Rifampicin resistance For rifampicin resistance detection, Xpert® MTB/RIF pooled sensitivity was 95% (95% CrI 90% to 97%; 17 studies, 555 rifampicin resistance positives) and pooled specificity was 98% (95% CrI 97% to 99%; 24 studies, 2411 rifampicin resistance negatives). Among 180 specimens with nontuberculous mycobacteria (NTM), Xpert® MTB/RIF was positive in only one specimen that grew NTM (14 studies, 2626 participants).For rifampicin resistance detection, if the pooled accuracy estimates for Xpert® MTB/RIF are applied to a hypothetical cohort of 1000 individuals where 15% of those with symptoms are rifampicin resistant, Xpert® MTB/RIF would correctly identify 143 individuals as rifampicin resistant and miss eight cases, and correctly identify 833 individuals as rifampicin susceptible and misclassify 17 individuals as resistant. Where 5% of those with symptoms are rifampicin resistant, Xpert® MTB/RIF would correctly identify 48 individuals as rifampicin resistant and miss three cases and correctly identify 931 individuals as rifampicin susceptible and misclassify 19 individuals as resistant.

AUTHORS' CONCLUSIONS

In adults thought to have TB, with or without HIV infection, Xpert® MTB/RIF is sensitive and specific. Compared with smear microscopy, Xpert® MTB/RIF substantially increases TB detection among culture-confirmed cases. Xpert® MTB/RIF has higher sensitivity for TB detection in smear-positive than smear-negative patients. Nonetheless, this test may be valuable as an add-on test following smear microscopy in patients previously found to be smear-negative. For rifampicin resistance detection, Xpert® MTB/RIF provides accurate results and can allow rapid initiation of MDR-TB treatment, pending results from conventional culture and DST. The tests are expensive, so current research evaluating the use of Xpert® MTB/RIF in TB programmes in high TB burden settings will help evaluate how this investment may help start treatment promptly and improve outcomes.

Biomarkers of tuberculosis: a research roadmap

Tuberculosis (TB) continues to represent a major public health problem worldwide. Prompt and accurate diagnosis and effective treatment are fundamental to reducing morbidity and mortality and curtailing spread of infection. Furthermore, tackling the large reservoir of latent infection is the cornerstone to TB control in many high income low TB incidence countries. However, our existing toolkit for prevention, diagnosis and treatment remains outdated and inadequate. Here, we discuss the key targets for biomarker research and discovery in TB and recent developments in the field. We focus on host biomarkers, in particular: correlates of vaccine efficacy and sterilizing immunity; biomarkers of latent TB infection, including diagnosis, risk of progression to active TB and response to treatment; and markers of active TB, including diagnosis, response to treatment and risk of relapse. Recent scientific and technological advances have contributed to significant recent progression in biomarker discovery. Although there are clear remaining paucities, continued efforts within scientific, translational and clinical studies are likely to yield a number of clinically useful biomarkers of TB in the foreseeable future.

Diagnosis of pulmonary tuberculosis

PURPOSE OF REVIEW

This review summarizes the recent literature on the developments in diagnostics for pulmonary tuberculosis (TB).

RECENT FINDINGS

A growing body of literature regarding the Xpert MTB/RIF assay confirms the high diagnostic accuracy in a range of clinical settings, including amongst inpatients, those with HIV coinfection and in children with culture-positive disease. Early experiences with operational implementation are now being reported from South Africa. Initial small-scale evaluations suggest that newer versions of line-probe assays have diagnostic accuracy similar to that of the Xpert MTB/RIF assay. Next-generation fully automated molecular assays that use isothermal amplification may in the future be more readily implemented at the point of care. The first low-cost, lateral-flow (strip-test) assay for lipoarabinomannan in urine shows promise as a rapid point-of-care test for TB amongst HIV-infected patients who have advanced immunodeficiency. A range of other diagnostic tools are also at various stages of development.

SUMMARY

There is continued momentum and optimism regarding the developments in TB diagnostics. However, studies of clinical and programmatic impact and operational research are needed to guide implementation and scale-up of new assays in resource-limited settings. Further concerted efforts are needed to develop point-of-care assays which are desperately needed to accelerate progress in TB control.

Performance monitoring of mycobacterium tuberculosis dried culture spots for use with the GeneXpert system within a national program in South Africa

The use of dried culture spots (DCSs) has been reported in the verification of GeneXpert instruments as being "fit for purpose" for the South African National implementation program. We investigated and compared the performance of the DCSs for verification across different bulk batches, testing the settings and cadre of staff, and the Xpert MTB/RIF assay version. Four bulk batches (V005 to V008) were used to prepare (i) 619 DCS panels for laboratory testing on G3 or G4 cartridges by a technologist, (ii) 13 DCS panels (batch V005) used for clinic verification on G3 cartridges by a nurse or lay counselor, and (iii) 20 DCS panels (batch V005) used for the verification of 10 GeneXpert 16 module instruments in mobile vehicles on the G3 cartridge performed by a scientist. The stabilities of the DCSs over 6 months at 4°C, room temperature, and 37°C were investigated. The mean cycle threshold (CT) and standard deviation (SD) for probe A were calculated. The proportions of variability in the CT values across bulk batches, assay versions, and settings and cadre of staff were determined using regression analysis. Overall, the DCSs demonstrated SDs of 3.3 (n = 660) for the G3 cartridges and 3.8 (n = 1,888) for the G4 cartridges, with an overall error rate of 1.5% and false rifampin resistance rate of 0.1%. The proportions of variability (R(2)) in the CT values explained by batch were 14%, by setting and cadre of staff, 5.6%, and by assay version, 4.2%. The most stable temperature in a period of up to 6 months was 37°C (SD, 2.7). The DCS is a robust product suitable for storage, transport, and use at room temperature for the verification of the GeneXpert instrument, and the testing can be performed by non-laboratory-trained personnel in nonlaboratory settings.

Using Xpert MTB/RIF

Xpert MTB/RIF is an automated real-time polymerase chain reaction test for simultaneous detection of tuberculosis and rifampicin resistance. Xpert MTB/RIF has demonstrated excellent accuracy in clinical evaluation studies, but has reduced sensitivity for detection of smear-negative tuberculosis. Since sample processing and detection are largely automated, Xpert MTB/RIF is potentially suitable for implementation in resource-limited settings. There are, however, a number of practical constraints to the use of Xpert at the point-of-care. Xpert remains a relatively costly test, and clear demonstration of cost-effectiveness will be needed to support efforts to scale up testing in high burden countries.

Time to treatment and patient outcomes among TB suspects screened by a single point-of-care xpert MTB/RIF at a primary care clinic in Johannesburg, South Africa

INTRODUCTION

In December 2010, the World Health Organization recommended a single Xpert MTB/RIF assay as the initial diagnostic in people suspected of HIV-associated or drug resistant tuberculosis. Few data are available on the impact of this recommendation on patient outcomes. We describe the diagnostic follow-up, clinical characteristics and outcomes of a cohort of tuberculosis suspects screened using a single point-of-care Xpert.

METHODS

Consecutive tuberculosis suspects at a primary care clinic in Johannesburg, South Africa were assessed for tuberculosis using point-of-care Xpert. Sputum smear microscopy and liquid culture were performed as reference standards. Xpert-negatives were evaluated clinically, and further assessed at the discretion of clinicians. Participants were followed for six months.

RESULTS

From July-September 2011, 641 tuberculosis suspects were enrolled, of whom 69% were HIV-infected. Eight percent were positive by a single Xpert. Among 116 individuals diagnosed with TB, 66 (57%) were Xpert negative, of which 44 (67%) were empirical or radiological diagnoses and 22 (33%) were Xpert negative/culture-positive. The median time to tuberculosis treatment was 0 days (IQR: 0-0) for Xpert positives, 14 days (IQR: 5-35) for those diagnosed empirically, 14 days (IQR: 7-29) for radiological diagnoses, and 144 days (IQR: 28-180) for culture positives. Xpert negative tuberculosis cases were clinically similar to Xpert positives, including HIV status and CD4 count, and had similar treatment outcomes including mortality and time to antiretroviral treatment initiation.

CONCLUSIONS

In a high HIV-burden setting, a single Xpert identified less than half of those started on tuberculosis treatment, highlighting the complexity of TB diagnosis even in the Xpert era. Xpert at point-of-care resulted in same day treatment initiation in Xpert-positives, but had no impact on tuberculosis treatment outcomes or mortality.

Alignment of new tuberculosis drug regimens and drug susceptibility testing: a framework for action

New tuberculosis drug regimens are creating new priorities for drug susceptibility testing (DST) and surveillance. To minimise turnaround time, rapid DST will need to be prioritised, but developers of these assays will need better data about the molecular mechanisms of resistance. Efforts are underway to link mutations with drug resistance and to develop strain collections to enable assessment of new diagnostic assays. In resource-limited settings, DST might not be appropriate for all patients with tuberculosis. Surveillance data and modelling will help country stakeholders to design appropriate DST algorithms and to decide whether to change drug regimens. Finally, development of practical DST assays is needed so that, in countries where surveillance and modelling show that DST is advisable, these assays can be used to guide clinical decisions for individual patients. If combined judiciously during both development and implementation, new tuberculosis regimens and new DST assays have enormous potential to improve patient outcomes and reduce the burden of disease.

Advances in tuberculosis diagnostics: the Xpert MTB/RIF assay and future prospects for a point-of-care test

Rapid progress has been made in the development of new diagnostic assays for tuberculosis in recent years. New technologies have been developed and assessed, and are now being implemented. The Xpert MTB/RIF assay, which enables simultaneous detection of Mycobacterium tuberculosis (MTB) and rifampicin (RIF) resistance, was endorsed by WHO in December, 2010. This assay was specifically recommended for use as the initial diagnostic test for suspected drug-resistant or HIV-associated pulmonary tuberculosis. By June, 2012, two-thirds of countries with a high tuberculosis burden and half of countries with a high multidrug-resistant tuberculosis burden had incorporated the assay into their national tuberculosis programme guidelines. Although the development of the Xpert MTB/RIF assay is undoubtedly a landmark event, clinical and programmatic effects and cost-effectiveness remain to be defined. We review the rapidly growing body of scientific literature and discuss the advantages and challenges of using the Xpert MTB/RIF assay in areas where tuberculosis is endemic. We also review other prospects within the developmental pipeline. A rapid, accurate point-of-care diagnostic test that is affordable and can be readily implemented is urgently needed. Investment in the tuberculosis diagnostics pipeline should remain a major priority for funders and researchers.

Xpert® MTB/RIF assay for pulmonary tuberculosis and rifampicin resistance in adults

BACKGROUND

Accurate and rapid detection of tuberculosis (TB) and drug resistance are critical for improving patient care and decreasing the spread of TB. Xpert® MTB/RIF assay (Xpert) is a rapid, automated test that can detect both TB and rifampicin resistance, within two hours after starting the test, with minimal hands-on technical time, but is more expensive than conventional sputum microscopy.

OBJECTIVES

To assess the diagnostic accuracy of Xpert for pulmonary TB (TB detection), both where Xpert was used as an initial test replacing microscopy, and where Xpert was used as an add-on test following a negative smear microscopy result.To assess the diagnostic accuracy of Xpert for rifampicin resistance detection where Xpert was used as the initial test, replacing conventional culture-based drug susceptibility testing.The population of interest was adults suspected of having pulmonary TB or multidrug-resistant TB (MDR-TB), with or without HIV infection.

SEARCH METHODS

We performed a comprehensive search of the following databases: Cochrane Infectious Diseases Group Specialized Register; MEDLINE; EMBASE; ISI Web of Knowledge; MEDION; LILACS; BIOSIS; and SCOPUS. We also searched the metaRegister of Controlled Trials (mRCT) and the search portal of the WHO International Clinical Trials Registry Platform to identify ongoing trials. We performed searches on 25 September 2011 and we repeated them on 15 December 2011, without language restriction.

SELECTION CRITERIA

We included randomized controlled trials, cross-sectional, and cohort studies that used respiratory specimens to compare Xpert with culture for detecting TB and Xpert with conventional phenotypic drug susceptibility testing for detecting rifampicin resistance.

DATA COLLECTION AND ANALYSIS

For each study, two review authors independently extracted a set of data using a standardized data extraction form. When possible, we extracted data for subgroups by smear and HIV status. We assessed the quality of studies using the QUADAS-2 tool. We carried out meta-analyses to estimate the pooled sensitivity and specificity of Xpert separately for TB detection and rifampicin resistance detection using a bivariate random-effects model. We estimated the median pooled sensitivity and specificity and their 95% credible intervals (CrI).

MAIN RESULTS

We identified 18 unique studies as eligible for this review, including two multicentre international studies, one with five and the other with six distinct study centres. The majority of studies (55.6%) were performed in low-income and middle-income countries. In 17 of the 18 studies, Xpert was performed by trained technicians in reference laboratories.When used as an initial test replacing smear microscopy (15 studies, 7517 participants), Xpert achieved a pooled sensitivity of 88% (95% CrI 83% to 92%) and pooled specificity of 98% (95% CrI 97% to 99%). As an add-on test following a negative smear microscopy result (14 studies, 5719 participants), Xpert yielded a pooled sensitivity of 67% (95% CrI 58% to 74%) and pooled specificity of 98% (95% CrI 97% to 99%). In clinical subgroups, we found the following accuracy estimates: the pooled sensitivity was 98% (95% CrI 97% to 99%) for smear-positive, culture-positive TB and 68% (95% CrI 59% to 75%) for smear-negative, culture-positive TB (15 studies); the pooled sensitivity was 80% (95% CrI 67% to 88%) in people living with HIV and 89% (95% CrI 81% to 94%) in people without HIV infection (four studies). For rifampicin resistance detection (11 studies, 2340 participants), Xpert achieved a pooled sensitivity of 94% (95% CrI 87% to 97%) and pooled specificity of 98% (95% CrI 97% to 99%). In a separate analysis, Xpert could distinguish between TB and nontuberculous mycobacteria (NTM) in clinical samples with high accuracy: among 139 specimens with NTM, Xpert was positive in only one specimen that grew NTM.In a hypothetical cohort of 1000 individuals suspected of having rifampicin resistance (a proxy for MDR-TB), where the prevalence of rifampicin resistance is 30%, we estimated that on average Xpert would wrongly identify 14 patients as being rifampicin resistant. In comparison, where the prevalence of rifampicin resistance is only 2%, we estimated that the number of individuals wrongly identified as rifampicin resistant would increase to 20, an increase of 43%.

AUTHORS' CONCLUSIONS

This review shows that Xpert used as an initial diagnostic test for TB detection and rifampicin resistance detection in patients suspected of having TB, MDR-TB, or HIV-associated TB is sensitive and specific. Xpert may also be valuable as an add-on test following microscopy for patients who have previously been found to be smear-negative. An Xpert result that is positive for rifampicin resistance should be carefully interpreted and take into consideration the risk of MDR-TB in a given patient and the expected prevalence of MDR-TB in a given setting.Studies in this review mainly assessed sensitivity and specificity of the test when used in reference laboratories in research investigations. Most studies were performed in high TB burden countries. Ongoing use of Xpert in high TB burden countries will contribute to the evidence base on the diagnostic accuracy and clinical impact of Xpert in routine programmatic and peripheral health care settings, including settings where the test is performed at the point of care.

State of affairs of tuberculosis in prison facilities: a systematic review of screening practices and recommendations for best TB control

Background

Prisoners are at high risk of developing tuberculosis (TB), causing morbidity and mortality. Prison facilities encounter many challenges in TB screening procedures and TB control. This review explores screening practices for detection of TB and describes limitations of TB control in prison facilities worldwide.

Methods

A systematic search of online databases (e.g., PubMed and Embase) and conference abstracts was carried out. Research papers describing screening and diagnostic practices among prisoners were included. A total of 52 articles met the inclusion criteria. A meta-analysis of TB prevalence in prison facilities by screening and diagnostic tools was performed.

Results

The most common screening tool was symptom questionnaires (63·5%), mostly reporting presence of cough. Microscopy of sputum with Ziehl-Neelsen staining and solid culture were the most frequently combined diagnostic methods (21·2%). Chest X-ray and tuberculin skin tests were used by 73·1% and 50%, respectively, as either a screening and/or diagnostic tool. Median TB prevalence among prisoners of all included studies was 1,913 cases of TB per 100,000 prisoners (interquartile range [IQR]: 332–3,517). The overall annual median TB incidence was 7·0 cases per 1000 person-years (IQR: 2·7–30·0). Major limitations for successful TB control were inaccuracy of diagnostic algorithms and the lack of adequate laboratory facilities reported by 61·5% of studies. The most frequent recommendation for improving TB control and case detection was to increase screening frequency (73·1%).

Discussion

TB screening algorithms differ by income area and should be adapted to local contexts. In order to control TB, prison facilities must improve laboratory capacity and frequent use of effective screening and diagnostic tools. Sustainable political will and funding are critical to achieve this.

Population health impact and cost-effectiveness of tuberculosis diagnosis with Xpert MTB/RIF: a dynamic simulation and economic evaluation

BACKGROUND

The Xpert MTB/RIF test enables rapid detection of tuberculosis (TB) and rifampicin resistance. The World Health Organization recommends Xpert for initial diagnosis in individuals suspected of having multidrug-resistant TB (MDR-TB) or HIV-associated TB, and many countries are moving quickly toward adopting Xpert. As roll-out proceeds, it is essential to understand the potential health impact and cost-effectiveness of diagnostic strategies based on Xpert.

METHODS AND FINDINGS

We evaluated potential health and economic consequences of implementing Xpert in five southern African countries--Botswana, Lesotho, Namibia, South Africa, and Swaziland--where drug resistance and TB-HIV coinfection are prevalent. Using a calibrated, dynamic mathematical model, we compared the status quo diagnostic algorithm, emphasizing sputum smear, against an algorithm incorporating Xpert for initial diagnosis. Results were projected over 10- and 20-y time periods starting from 2012. Compared to status quo, implementation of Xpert would avert 132,000 (95% CI: 55,000-284,000) TB cases and 182,000 (97,000-302,000) TB deaths in southern Africa over the 10 y following introduction, and would reduce prevalence by 28% (14%-40%) by 2022, with more modest reductions in incidence. Health system costs are projected to increase substantially with Xpert, by US$460 million (294-699 million) over 10 y. Antiretroviral therapy for HIV represents a substantial fraction of these additional costs, because of improved survival in TB/HIV-infected populations through better TB case-finding and treatment. Costs for treating MDR-TB are also expected to rise significantly with Xpert scale-up. Relative to status quo, Xpert has an estimated cost-effectiveness of US$959 (633-1,485) per disability-adjusted life-year averted over 10 y. Across countries, cost-effectiveness ratios ranged from US$792 (482-1,785) in Swaziland to US$1,257 (767-2,276) in Botswana. Assessing outcomes over a 10-y period focuses on the near-term consequences of Xpert adoption, but the cost-effectiveness results are conservative, with cost-effectiveness ratios assessed over a 20-y time horizon approximately 20% lower than the 10-y values.

CONCLUSIONS

Introduction of Xpert could substantially change TB morbidity and mortality through improved case-finding and treatment, with more limited impact on long-term transmission dynamics. Despite extant uncertainty about TB natural history and intervention impact in southern Africa, adoption of Xpert evidently offers reasonable value for its cost, based on conventional benchmarks for cost-effectiveness. However, the additional financial burden would be substantial, including significant increases in costs for treating HIV and MDR-TB. Given the fundamental influence of HIV on TB dynamics and intervention costs, care should be taken when interpreting the results of this analysis outside of settings with high HIV prevalence.

Point-of-care testing for infectious diseases: diversity, complexity, and barriers in low- and middle-income countries

Madhukar Pai and colleagues discuss a framework for envisioning how point-of-care testing can be applied to infectious diseases in low- and middle-income countries.