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

A Generalizable Decision-Making Framework for Selecting Onsite versus Send-out Clinical Laboratory Testing

BACKGROUND

Laboratory networks provide services through onsite testing or through specimen transport to higher-tier laboratories. This decision is based on the interplay of testing characteristics, treatment characteristics, and epidemiological characteristics.

OBJECTIVES

Our objective was to develop a generalizable model using the threshold approach to medical decision making to inform test placement decisions.

METHODS

We developed a decision model to compare the incremental utility of onsite versus send-out testing for clinical purposes. We then performed Monte Carlo simulations to identify the settings under which each strategy would be preferred. Tuberculosis was modeled as an exemplar.

RESULTS

The most important determinants of the decision to test onsite versus send-out were the clinical utility lost due to send-out testing delays and the accuracy decrement with onsite testing. When the sensitivity decrements of onsite testing were minimal, onsite testing tended to be preferred when send-out delays reduced clinical utility by >20%. By contrast, when onsite testing incurred large reductions in sensitivity, onsite testing tended to be preferred when utility lost due to delays was >50%. The relative cost of onsite versus send-out testing affected these thresholds, particularly when testing costs were >10% of treatment costs.

CONCLUSIONS

Decision makers can select onsite versus send-out testing in an evidence-based fashion using estimates of the percentage of clinical utility lost due to send-out delays and the relative accuracy of onsite versus send-out testing. This model is designed to be generalizable to a wide variety of use cases.

HIGHLIGHTS

The design of laboratory networks, including the decision to place diagnostic instruments at the point-of-care or at higher tiers as accessed through specimen transport, can be informed using the threshold approach to medical decision making.The most important determinants of the decision to test onsite versus send-out were the clinical utility lost due to send-out testing delays and the accuracy decrement with onsite testing.The threshold approach to medical decision making can be used to compare point-of-care testing accuracy decrements with the lost utility of treatment due to send-out testing delays.The relative cost of onsite versus send-out testing affected these thresholds, particularly when testing costs were >10% of treatment costs.

Cost-effectiveness of Low-complexity Screening Tests in Community-based Case-finding for Tuberculosis

INTRODUCTION

In high-burden settings, low-complexity screening tests for tuberculosis (TB) could expand the reach of community-based case-finding efforts. The potential costs and cost-effectiveness of approaches incorporating these tests are poorly understood.

METHODS

We developed a microsimulation model assessing 3 approaches to community-based case-finding in hypothetical populations (India-, South Africa-, The Philippines-, Uganda-, and Vietnam-like settings) with TB prevalence 4 times that of national estimates: (1) screening with a point-of-care C-reactive protein (CRP) test, (2) screening with a more sensitive "Hypothetical Screening test" (95% sensitive for Xpert Ultra-positive TB, 70% specificity; equipment/labor costs similar to Xpert Ultra, but using a $2 cartridge) followed by sputum Xpert Ultra if positive, or (3) testing all individuals with sputum Xpert Ultra. Costs are expressed in 2023 US dollars and include treatment costs.

RESULTS

Universal Xpert Ultra was estimated to cost a mean $4.0 million (95% uncertainty range: $3.5 to $4.6 million) and avert 3200 (2600 to 3900) TB-related disability-adjusted life years (DALYs) per 100 000 people screened ($670 [The Philippines] to $2000 [Vietnam] per DALY averted). CRP was projected to cost $550 (The Philippines) to $1500 (Vietnam) per DALY averted but with 44% fewer DALYs averted. The Hypothetical Screening test showed minimal benefit compared to universal Xpert Ultra, but if specificity were improved to 95% and per-test cost to $4.5 (all-inclusive), this strategy could cost $390 (The Philippines) to $940 (Vietnam) per DALY averted.

CONCLUSIONS

Screening tests can meaningfully improve the cost-effectiveness of community-based case-finding for TB but only if they are sensitive, specific, and inexpensive.

Impact and cost-effectiveness of short-course tuberculosis preventive treatment for household contacts and people with HIV in 29 high-incidence countries: a modelling analysis

BACKGROUND

Guidelines and implementation of tuberculosis preventive treatment (TPT) vary by age and HIV status. Specifically, TPT is strongly recommended for people living with HIV/AIDS (PLWHA) and household contacts younger than 5 years but only conditionally recommended for older contacts. Cost remains a major barrier to implementation. The aim of this study was to evaluate the cost-effectiveness of TPT for household contacts and PLWHA.

METHODS

We developed a state-transition model to simulate short-course TPT for household contacts and PLWHA in 29 high-incidence countries based on data from previous studies and public databases. Our primary outcome was the incremental cost-effectiveness ratio, expressed as incremental discounted costs (2020 US$, including contact investigation costs) per incremental discounted disability-adjusted life year (DALY) averted, compared with a scenario without any TPT or contact investigation. We propagated uncertainty in all model parameters using probabilistic sensitivity analysis and also evaluated the sensitivity of results to the screening algorithm used to rule out active disease, the choice of TPT regimen, the modelling time horizon, assumptions about TPT coverage, antiretroviral therapy discontinuation, and secondary transmission.

FINDINGS

Between 2023 and 2035, scaling up TPT prevented 0·9 (95% uncertainty interval 0·4-1·6) people from developing tuberculosis and 0·13 (0·05-0·27) tuberculosis deaths per 100 PLWHA, at an incremental cost of $15 (9-21) per PLWHA. For household contacts, TPT (with contact investigation) averted 1·1 (0·5-2·0) cases and 0·7 (0·4-1·0) deaths per 100 contacts, at a cost of $21 (17-25) per contact. Cost-effectiveness was most favourable for household contacts younger than 5 years ($22 per DALY averted) and contacts aged 5-14 years ($104 per DALY averted) but also fell within conservative cost-effectiveness thresholds in many countries for PLWHA ($722 per DALY averted) and adult contacts ($309 per DALY averted). Costs per DALY averted tended to be lower when compared with a scenario with contact investigation but no TPT. The cost-effectiveness of TPT was not substantially altered in sensitivity analyses, except that TPT was more favourable in analysis that considered a longer time horizon or included secondary transmission benefits.

INTERPRETATION

In many high-incidence countries, short-course TPT is likely to be cost-effective for PLWHA and household contacts of all ages, regardless of whether contact investigation is already in place. Failing to implement tuberculosis contact investigation and TPT will incur a large burden of avertable illness and mortality in the next decade.

FUNDING

Unitaid.

Rapid Detection of Extensive Drug Resistance by Xpert MTB/XDR Optimizes Therapeutic Decision-Making in Rifampin-Resistant Tuberculosis Patients

The Xpert MTB/XDR assay met the critical need for etiologic diagnosis of tuberculosis and rifampin resistance in previous studies. However, its benefits in tailoring the treatment regimen and improving the outcome for patients with rifampin-resistant tuberculosis (RR-TB) require further investigation. In this study, the Xpert MTB/XDR assay was used to determine the resistance profile of second-line drugs for RR-TB patients in two registered multicenter clinical trials, TB-TRUST (NCT03867136) and TB-TRUST-plus (NCT04717908), with the aim of testing the efficacy of all-oral shorter regimens in RR-TB patients in China. Patients would receive the fluoroquinolone-based all-oral shorter regimen, the injectable-containing regimen, or the bedaquiline-based regimen depending on fluoroquinolone susceptibility by using Xpert MTB/XDR. Among the 497 patients performed with Xpert MTB/XDR, 128 (25.8%) had infections resistant to fluoroquinolones and/or second-line injectable drugs (SLIDs). A total of 371 participants were recruited for the trials, and whole-genome sequencing (WGS) was performed on all corresponding culture-positive baseline strains. Taking the WGS results as the standard, the accuracy of the Xpert MTB/XDR assay in terms of resistance detection was 95.2% to 99.0% for all drugs. A total of 33 cases had inconsistent results, 9 of which were due to resistance heterogeneity. Most of the patients (241/281, 85.8%) had sputum culture conversion at 2 months. In conclusion, the Xpert MTB/XDR assay has the potential to serve as a quick reflex test in patients with RR-TB, as detected via Xpert MTB/RIF, to provide a reliable drug susceptibility profile of the infecting Mycobacterium tuberculosis strain and to initiate optimized treatment promptly.

Multicomponent strategy with decentralised molecular testing for tuberculosis in Uganda: a cost and cost-effectiveness analysis

BACKGROUND

Decentralised molecular testing for tuberculosis could reduce missed diagnoses and losses to follow-up in high-burden settings. The aim of this study was to evaluate the cost and cost-effectiveness of the Xpert Performance Evaluation for Linkage to Tuberculosis Care (XPEL-TB) study strategy, a multicomponent strategy including decentralised molecular testing for tuberculosis, in Uganda.

METHODS

We conducted a costing and cost-effectiveness analysis nested in a pragmatic cluster-randomised trial of onsite (decentralised) versus hub-and-spoke (centralised) testing for tuberculosis with Xpert MTB/RIF Ultra (Xpert) in 20 community health centres in Uganda. We collected empirical data on the cost of the XPEL-TB strategy (decentralised Xpert testing, workflow redesign, and performance feedback) and routine tuberculosis testing (onsite smear microscopy with specimen transport for centralised Xpert testing) from the health system perspective. Time-and-motion studies were performed to estimate activity-based service costs. Cost-effectiveness was assessed as the incremental cost (2019 US$) per tuberculosis diagnosis and per 14-day treatment initiation.

FINDINGS

The XPEL-TB study ran from Oct 22, 2018, to March 1, 2020. Effectiveness and cost-effectiveness outcomes were assessed from Dec 1, 2018, to Nov 30, 2019 and included 4867 women and 3139 men. On a per-test basis, the cost of decentralised ($20·46, range $17·85-25·72) and centralised ($18·20, range $16·58-24·25) Xpert testing was similar. However, decentralised testing resulted in more patients receiving appropriate Xpert testing, so the per-patient cost of decentralised testing was higher: $20·28 (range $17·68-25·48) versus $9·59 (range $7·62-14·34). The XPEL-TB strategy was estimated to cost $1332 (95% uncertainty range $763-5558) per incremental tuberculosis diagnosis and $687 ($501-1207) per incremental patient initiating tuberculosis treatment within 14 days. Cost-effectiveness was reduced in sites performing fewer than 150-250 tests annually.

INTERPRETATION

The XPEL-TB strategy facilitated higher rates of Xpert testing for tuberculosis at a similar per-test cost and modest incremental cost per tuberculosis diagnosis and treatment initiation. Decentralised Xpert testing, with appropriate implementation supports, should be scaled up to clinics with sufficient testing volume to support a single-module device.

FUNDING

The National Heart, Lung, and Blood Institute.

The Changing Paradigm of Drug-Resistant Tuberculosis Treatment: Successes, Pitfalls, and Future Perspectives

Drug-resistant tuberculosis (DR-TB) remains a global crisis due to the increasing incidence of drug-resistant forms of the disease, gaps in detection and prevention, models of care, and limited treatment options. The DR-TB treatment landscape has evolved over the last 10 years. Recent developments include the remarkable activity demonstrated by the newly approved anti-TB drugs bedaquiline and pretomanid against Mycobacterium tuberculosis. Hence, treatment of DR-TB has drastically evolved with the introduction of the short-course regimen for multidrug-resistant TB (MDR-TB), transitioning to injection-free regimens and the approval of the 6-month short regimens for rifampin-resistant TB and MDR-TB. Moreover, numerous clinical trials are under way with the aim to reduce pill burden and shorten the DR-TB treatment duration. While there have been apparent successes in the field, some challenges remain. These include the ongoing inclusion of high-dose isoniazid in DR-TB regimens despite a lack of evidence for its efficacy and the inclusion of ethambutol and pyrazinamide in the standard short regimen despite known high levels of background resistance to both drugs. Furthermore, antimicrobial heteroresistance, extensive cavitary disease and intracavitary gradients, the emergence of bedaquiline resistance, and the lack of biomarkers to monitor DR-TB treatment response remain serious challenges to the sustained successes. In this review, we outline the impact of the new drugs and regimens on patient treatment outcomes, explore evidence underpinning current practices on regimen selection and duration, reflect on the disappointments and pitfalls in the field, and highlight key areas that require continued efforts toward improving treatment approaches and rapid biomarkers for monitoring treatment response.

How to Realize the Benefits of Point-of-Care Testing at the General Practice: A Comparison of Four High-Income Countries

BACKGROUND

In some countries, such as the Netherlands and Norway, point-of-care testing (POCT) is more widely implemented in general practice compared to countries such as England and Australia. To comprehend what is necessary to realize the benefits of POCT, regarding its integration in primary care, it would be beneficial to have an overview of the structure of healthcare operations and the transactions between stakeholders (also referred to as value networks). The aim of this paper is to identify the current value networks in place applying to POCT implementation at general practices in England, Australia, Norway and the Netherlands and to compare these networks in terms of seven previously published factors that support the successful implementation, sustainability and scale-up of innovations.

METHODS

The value networks were described based on formal guidelines and standards published by the respective governments, organizational bodies and affiliates. The value network of each country was validated by at least two relevant stakeholders from the respective country.

RESULTS

The analysis revealed that the biggest challenge for countries with low POCT uptake was the lack of effective communication between the several organizations involved with POCT as well as the high workload for general practitioners (GPs) aiming to implement POCT. It is observed that countries with a single national authority responsible for POCT have a better uptake as they can govern the task of POCT roll-out and management and reduce the workload for GPs by assisting with set-up, quality control, training and support.

CONCLUSION

Setting up a single national authority may be an effective step towards realizing the full benefits of POCT. Although it is possible for day-to-day operations to fall under the responsibility of the GP, this is only feasible if support and guidance are readily available to ensure that the workload associated with POCT is limited and as low as possible.

Molecular genetic tests GeneXpert MTB/RIF and Xpert MTB/RIF (Ultra) in the diagnosis of tuberculosis (review of literature)

In recent tuberculosis years is the main cause of morbidity and death among patients with HIV infection. Modern diagnostics of tuberculosis includes mass screening of the population: digital fluorography from the age of 15 and immunodiagnostics in children and adolescents. Detection of mycobacterium tuberculosis by microscopy occurs in forms of tuberculosis with the decay of lung tissue. Such patients represent a high epidemic risk. To improve the verification of diagnosis in the practice of a phthisiologist, molecular genetic methods for the search for mycobacteria are increasingly used, based on the identification of specific fragments of the DNA chain in the diagnostic material. The most widely used method is the polymerase chain reaction (PCR), which is based on directed DNA amplification. The latest innovation is fully automated systems using cartridge technology GeneXpert. The advantages of GeneXpert are high sensitivity, speed (result in 2 hours), real-time PCR detection, exclusion of sample contamination. The technique of cartridge technology is constantly being improved, various cartridges are used on its platform, which not only detect M. tuberculosis, but also determine the sensitivity to anti-tuberculosis drugs - rifampicin (MTB / RIF cartridge) or several anti-TB drugs (MTB / XDR). Cartridges have been developed that are able to detect Mycobacterium tuberculosis (MBT) at an even lower concentration in the test material - MTB / RIF (Ultra). GeneXpert technology can be used to diagnose extrapulmonary tuberculosis by examining various biological materials, which are more effective in detecting tuberculosis in children and adolescents, in HIV-positive individuals.

Fluorescence In Situ Hybridization (FISH) Tests for Identifying Protozoan and Bacterial Pathogens in Infectious Diseases

Diagnosing and treating many infectious diseases depends on correctly identifying the causative pathogen. Characterization of pathogen-specific nucleic acid sequences by PCR is the most sensitive and specific method available for this purpose, although it is restricted to laboratories that have the necessary infrastructure and finance. Microscopy, rapid immunochromatographic tests for antigens, and immunoassays for detecting pathogen-specific antibodies are alternative and useful diagnostic methods with different advantages and disadvantages. Detection of ribosomal RNA molecules in the cytoplasm of bacterial and protozoan pathogens by fluorescence in-situ hybridization (FISH) using sequence-specific fluorescently labelled DNA probes, is cheaper than PCR and requires minimal equipment and infrastructure. A LED light source attached to most laboratory light microscopes can be used in place of a fluorescence microscope with a UV lamp for FISH. A FISH test hybridization can be completed in 30 min at 37 °C and the whole test in less than two hours. FISH tests can therefore be rapidly performed in both well-equipped and poorly-resourced laboratories. Highly sensitive and specific FISH tests for identifying many bacterial and protozoan pathogens that cause disease in humans, livestock and pets are reviewed, with particular reference to parasites causing malaria and babesiosis, and mycobacteria responsible for tuberculosis.

Rapid molecular tests for tuberculosis and tuberculosis drug resistance: a qualitative evidence synthesis of recipient and provider views

BACKGROUND

Programmes that introduce rapid molecular tests for tuberculosis and tuberculosis drug resistance aim to bring tests closer to the community, and thereby cut delay in diagnosis, ensure early treatment, and improve health outcomes, as well as overcome problems with poor laboratory infrastructure and inadequately trained personnel. Yet, diagnostic technologies only have an impact if they are put to use in a correct and timely manner. Views of the intended beneficiaries are important in uptake of diagnostics, and their effective use also depends on those implementing testing programmes, including providers, laboratory professionals, and staff in health ministries. Otherwise, there is a risk these technologies will not fit their intended use and setting, cannot be made to work and scale up, and are not used by, or not accessible to, those in need.

OBJECTIVES

To synthesize end-user and professional user perspectives and experiences with low-complexity nucleic acid amplification tests (NAATs) for detection of tuberculosis and tuberculosis drug resistance; and to identify implications for effective implementation and health equity.

SEARCH METHODS

We searched MEDLINE, Embase, CINAHL, PsycInfo and Science Citation Index Expanded databases for eligible studies from 1 January 2007 up to 20 October 2021. We limited all searches to 2007 onward because the development of Xpert MTB/RIF, the first rapid molecular test in this review, was completed in 2009.

SELECTION CRITERIA

We included studies that used qualitative methods for data collection and analysis, and were focused on perspectives and experiences of users and potential users of low-complexity NAATs to diagnose tuberculosis and drug-resistant tuberculosis. NAATs included Xpert MTB/RIF, Xpert MTB/RIF Ultra, Xpert MTB/XDR, and the Truenat assays. Users were people with presumptive or confirmed tuberculosis and drug-resistant tuberculosis (including multidrug-resistant (MDR-TB)) and their caregivers, healthcare providers, laboratory technicians and managers, and programme officers and staff; and were from any type of health facility and setting globally. MDR-TB is tuberculosis caused by resistance to at least rifampicin and isoniazid, the two most effective first-line drugs used to treat tuberculosis.

DATA COLLECTION AND ANALYSIS

We used a thematic analysis approach for data extraction and synthesis, and assessed confidence in the findings using GRADE CERQual approach. We developed a conceptual framework to illustrate how the findings relate.

MAIN RESULTS

We found 32 studies. All studies were conducted in low- and middle-income countries. Twenty-seven studies were conducted in high-tuberculosis burden countries and 21 studies in high-MDR-TB burden countries. Only one study was from an Eastern European country. While the studies covered a diverse use of low-complexity NAATs, in only a minority of studies was it used as the initial diagnostic test for all people with presumptive tuberculosis. We identified 18 review findings and grouped them into three overarching categories. Critical aspects users value People with tuberculosis valued reaching diagnostic closure with an accurate diagnosis, avoiding diagnostic delays, and keeping diagnostic-associated cost low. Similarly, healthcare providers valued aspects of accuracy and the resulting confidence in low-complexity NAAT results, rapid turnaround times, and keeping cost to people seeking a diagnosis low. In addition, providers valued diversity of sample types (for example, gastric aspirate specimens and stool in children) and drug resistance information. Laboratory professionals appreciated the improved ease of use, ergonomics, and biosafety of low-complexity NAATs compared to sputum microscopy, and increased staff satisfaction. Challenges reported to realizing those values People with tuberculosis and healthcare workers were reluctant to test for tuberculosis (including MDR-TB) due to fears, stigma, or cost concerns. Thus, low-complexity NAAT testing is not implemented with sufficient support or discretion to overcome barriers that are common to other approaches to testing for tuberculosis. Delays were reported at many steps of the diagnostic pathway owing to poor sample quality; difficulties with transporting specimens; lack of sufficient resources; maintenance of low-complexity NAATs; increased workload; inefficient work and patient flows; over-reliance on low-complexity NAAT results in lieu of clinical judgement; and lack of data-driven and inclusive implementation processes. These challenges were reported to lead to underutilization.  Concerns for access and equity The reported concerns included sustainable funding and maintenance and equitable use of resources to access low-complexity NAATs, as well as conflicts of interest between donors and people implementing the tests. Also, lengthy diagnostic delays, underutilization of low-complexity NAATs, lack of tuberculosis diagnostic facilities in the community, and too many eligibility restrictions hampered access to prompt and accurate testing and treatment. This was particularly the case for vulnerable groups, such as children, people with MDR-TB, or people with limited ability to pay. We had high confidence in most of our findings.

AUTHORS' CONCLUSIONS

Low-complexity diagnostics have been presented as a solution to overcome deficiencies in laboratory infrastructure and lack of skilled professionals. This review indicates this is misleading. The lack of infrastructure and human resources undermine the added value new diagnostics of low complexity have for recipients and providers. We had high confidence in the evidence contributing to these review findings. Implementation of new diagnostic technologies, like those considered in this review, will need to tackle the challenges identified in this review including weak infrastructure and systems, and insufficient data on ground level realities prior and during implementation, as well as problems of conflicts of interest in order to ensure equitable use of resources.

Point-of-care diagnostic tests for tuberculosis disease

Rapid diagnosis is one key pillar to end tuberculosis (TB). Point-of-care tests (POCTs) facilitate early detection, immediate treatment, and reduced transmission of TB disease. This Review evaluates current diagnostic assays endorsed by the World Health Organization and identifies the gaps between existing conventional tests and the ideal POCT. We discuss the commercial development of new rapid tests and research studies on nonsputum-based diagnostic biomarkers from both pathogen and host. Last, we highlight advances in integrated microfluidics technology that may aid the development of new POCTs.

Coronavirus Disease 2019 Diagnosis in Low- and Middle-Income Countries: The Big New Bully Disrupting TB and HIV Diagnostic Services

Coronavirus disease 2019 (COVID-19) undermines control of other infectious diseases. Diagnostics are critical in health care. This opinion paper explores approaches for leveraging diagnostics for COVID-19 while retaining diagnostics for other infectious diseases, including tuberculosis (TB) and HIV. The authors reflect on experiences with GeneXpert technology for TB detection and opportunities for integration with other diseases. They also reflect on benefits and risks of integration. Placement of diagnostics in laboratory networks is largely nonintegrated and designated for specific diseases. Restricting the use of diagnostics leaves gaps in detection of TB, HIV, malaria, and COVID-19. Integrated laboratory systems can lead to more efficient testing while increasing access to critical diagnostics. However, the authors have observed that HIV diagnosis within the TB diagnostic network displaced TB diagnosis. Subsequently, COVID-19 disrupted both TB and HIV diagnosis. The World Health Organization recommended rapid molecular diagnostic networks for infectious diseases and there is a need for more investment to achieve diagnostic capacity for TB, HIV, COVID-19, and other emerging infectious diseases. Integrated laboratory systems require mapping laboratory networks, assessing needs for each infectious disease, and identifying resources. Otherwise, diagnostic capacity for one infectious disease may displace another. Further, not all aspects of optimal diagnostic networks fit all infectious diseases, but many efficiencies can be gained where integration is possible.

The Role of GeneXpert MTB/RIF in Reducing Treatment Delay Among Multidrug Resistance Tuberculosis Patients: A Propensity Score Matched Analysis

Background

Methods

Results

Conclusion

Economic Analyses of Respiratory Tract Infection Diagnostics: A Systematic Review

BACKGROUND

Diagnostic testing for respiratory tract infections is a tool to manage the current COVID-19 pandemic, as well as the rising incidence of antimicrobial resistance. At the same time, new European regulations for market entry of in vitro diagnostics, in the form of the in vitro diagnostic regulation, may lead to more clinical evidence supporting health-economic analyses.

OBJECTIVE

The objective of this systematic review was to review the methods used in economic evaluations of applied diagnostic techniques, for all patients seeking care for infectious diseases of the respiratory tract (such as pneumonia, pulmonary tuberculosis, influenza, sinusitis, pharyngitis, sore throats and general respiratory tract infections).

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, articles from three large databases of scientific literature were included (Scopus, Web of Science and PubMed) for the period January 2000 to May 2020.

RESULTS

A total of 70 economic analyses are included, most of which use decision tree modelling for diagnostic testing for respiratory tract infections in the community-care setting. Many studies do not incorporate a generally comparable clinical outcome in their cost-effectiveness analysis: fewer than half the studies (33/70) used generalisable outcomes such as quality-adjusted life-years. Other papers consider outcomes related to the accuracy of the test or outcomes related to the prescribed treatment. The time horizons of the studies generally are limited.

CONCLUSIONS

The methods to economically assess diagnostic tests for respiratory tract infections vary and would benefit from clear recommendations from policy makers on the assessed time horizon and outcomes used.

Derivation and external validation of a risk score for predicting HIV-associated tuberculosis to support case finding and preventive therapy scale-up: A cohort study

BACKGROUND

Among people living with HIV (PLHIV), more flexible and sensitive tuberculosis (TB) screening tools capable of detecting both symptomatic and subclinical active TB are needed to (1) reduce morbidity and mortality from undiagnosed TB; (2) facilitate scale-up of tuberculosis preventive therapy (TPT) while reducing inappropriate prescription of TPT to PLHIV with subclinical active TB; and (3) allow for differentiated HIV-TB care.

METHODS AND FINDINGS

We used Botswana XPRES trial data for adult HIV clinic enrollees collected during 2012 to 2015 to develop a parsimonious multivariable prognostic model for active prevalent TB using both logistic regression and random forest machine learning approaches. A clinical score was derived by rescaling final model coefficients. The clinical score was developed using southern Botswana XPRES data and its accuracy validated internally, using northern Botswana data, and externally using 3 diverse cohorts of antiretroviral therapy (ART)-naive and ART-experienced PLHIV enrolled in XPHACTOR, TB Fast Track (TBFT), and Gugulethu studies from South Africa (SA). Predictive accuracy of the clinical score was compared with the World Health Organization (WHO) 4-symptom TB screen. Among 5,418 XPRES enrollees, 2,771 were included in the derivation dataset; 67% were female, median age was 34 years, median CD4 was 240 cells/μL, 189 (7%) had undiagnosed prevalent TB, and characteristics were similar between internal derivation and validation datasets. Among XPHACTOR, TBFT, and Gugulethu cohorts, median CD4 was 400, 73, and 167 cells/μL, and prevalence of TB was 5%, 10%, and 18%, respectively. Factors predictive of TB in the derivation dataset and selected for the clinical score included male sex (1 point), ≥1 WHO TB symptom (7 points), smoking history (1 point), temperature >37.5°C (6 points), body mass index (BMI) <18.5kg/m2 (2 points), and severe anemia (hemoglobin <8g/dL) (3 points). Sensitivity using WHO 4-symptom TB screen was 73%, 80%, 94%, and 94% in XPRES, XPHACTOR, TBFT, and Gugulethu cohorts, respectively, but increased to 88%, 87%, 97%, and 97%, when a clinical score of ≥2 was used. Negative predictive value (NPV) also increased 1%, 0.3%, 1.6%, and 1.7% in XPRES, XPHACTOR, TBFT, and Gugulethu cohorts, respectively, when the clinical score of ≥2 replaced WHO 4-symptom TB screen. Categorizing risk scores into low (<2), moderate (2 to 10), and high-risk categories (>10) yielded TB prevalence of 1%, 1%, 2%, and 6% in the lowest risk group and 33%, 22%, 26%, and 32% in the highest risk group for XPRES, XPHACTOR, TBFT, and Gugulethu cohorts, respectively. At clinical score ≥2, the number needed to screen (NNS) ranged from 5.0 in Gugulethu to 11.0 in XPHACTOR. Limitations include that the risk score has not been validated in resource-rich settings and needs further evaluation and validation in contemporary cohorts in Africa and other resource-constrained settings.

CONCLUSIONS

The simple and feasible clinical score allowed for prioritization of sensitivity and NPV, which could facilitate reductions in mortality from undiagnosed TB and safer administration of TPT during proposed global scale-up efforts. Differentiation of risk by clinical score cutoff allows flexibility in designing differentiated HIV-TB care to maximize impact of available resources.

Unlocking the health system barriers to maximise the uptake and utilisation of molecular diagnostics in low-income and middle-income country setting

BACKGROUND

Early access to diagnosis is crucial for effective management of any disease including tuberculosis (TB). We investigated the barriers and opportunities to maximise uptake and utilisation of molecular diagnostics in routine healthcare settings.

METHODS

Using the implementation of WHO approved TB diagnostics, Xpert Mycobacterium tuberculosis/rifampicin (MTB/RIF) and Line Probe Assay (LPA) as a benchmark, we evaluated the barriers and how they could be unlocked to maximise uptake and utilisation of molecular diagnostics.

RESULTS

Health officers representing 190 districts/counties participated in the survey across Kenya, Tanzania and Uganda. The survey findings were corroborated by 145 healthcare facility (HCF) audits and 11 policy-maker engagement workshops. Xpert MTB/RIF coverage was 66%, falling behind microscopy and clinical diagnosis by 33% and 1%, respectively. Stratified by HCF type, Xpert MTB/RIF implementation was 56%, 96% and 95% at district, regional and national referral hospital levels. LPA coverage was 4%, 3% below culture across the three countries. Out of 111 HCFs with Xpert MTB/RIF, 37 (33%) used it to full capacity, performing ≥8 tests per day of which 51% of these were level five (zonal consultant and national referral) HCFs. Likewise, 75% of LPA was available at level five HCFs. Underutilisation of Xpert MTB/RIF and LPA was mainly attributed to inadequate-utilities, 26% and human resource, 22%. Underfinancing was the main reason underlying failure to acquire molecular diagnostics. Second to underfinancing was lack of awareness with 33% healthcare administrators and 49% practitioners were unaware of LPA as TB diagnostic. Creation of a national health tax and decentralising its management was proposed by policy-makers as a booster of domestic financing needed to increase access to diagnostics.

CONCLUSION

Our findings suggest higher uptake and utilisation of molecular diagnostics at tertiary level HCFs contrary to the WHO recommendation. Country-led solutions are crucial for unlocking barriers to increase access to diagnostics.

A Framework for Assessing Import Costs of Medical Supplies and Results for a Tuberculosis Program in Karakalpakstan, Uzbekistan

Background. Import of medical supplies is common, but limited knowledge about import costs and their structure introduces uncertainty to budget planning, cost management, and cost-effectiveness analysis of health programs. We aimed to estimate the import costs of a tuberculosis (TB) program in Uzbekistan, including the import costs of specific imported items.Methods. We developed a framework that applies costing and cost accounting to import costs. First, transport costs, customs-related costs, cargo weight, unit weights, and quantities ordered were gathered for a major shipment of medical supplies from the Médecins Sans Frontières (MSF) Procurement Unit in Amsterdam, the Netherlands, to a TB program in Karakalpakstan, Uzbekistan, in 2016. Second, air freight, land freight, and customs clearance cost totals were estimated. Third, total import costs were allocated to different cargos (standard, cool, and frozen), items (e.g., TB drugs), and units (e.g., one tablet) based on imported weight and quantity. Data sources were order invoices, waybills, the local MSF logistics department, and an MSF standard product list.Results. The shipment contained 1.8 million units of 85 medical items of standard, cool, and frozen cargo. The average import cost for the TB program was 9.0% of the shipment value. Import cost varied substantially between cargos (8.9-28% of the cargo value) and items (interquartile range 4.5-35% of the item value). The largest portion of the total import cost was caused by transport (82-99% of the cargo import cost) and allocated based on imported weight. Ten (14%) of the 69 items imported as standard cargo were associated with 85% of the standard cargo import cost. Standard cargo items could be grouped based on contributing to import costs predominantly through unit weight (e.g., fluids), imported quantity (e.g., tablets), or the combination of unit weight and imported quantity (e.g., items in powder form).Conclusion. The cost of importing medical supplies to a TB program in Karakalpakstan, Uzbekistan, was sizable, variable, and driven by a subset of imported items. The framework used to measure and account import costs can be adapted to other health programs.

Evaluating urban-rural access to pathology and laboratory medicine services in Tanzania

Placement of pathology and laboratory medicine (PALM) services requires balancing efficiency (maximizing test volume) with equitable urban-rural access. We compared the association between population density (proxy for efficiency) and travel time to the closest facility (proxy for equitable access) across levels of Tanzania's public sector health system. We linked geospatial data for Tanzania from multiple sources. Data on facility locations and other geographic measures were collected from government and non-governmental databases. We classified facilities assuming increasing PALM availability by tier: (1) dispensaries, (2) health centres, (3) district hospitals and (4) regional/referral hospitals. We used the AccessMod 5 algorithm to estimate travel time to the closest facility for each tier across Tanzania with 500-m resolution. District-level average population density and travel time to the closest facility were calculated and presented using medians and interquartile ranges. Spatial correlations between these variables were estimated using the global Moran's I and bivariate Local Indicator of Spatial Autocorrelation, specifying a queen's neighbourhood matrix. Spatial analysis was restricted to 171 contiguous districts. The study included 5406 dispensaries, 675 health centres, 186 district hospitals and 37 regional/referral hospitals. District-level travel times were shortest for Tier 1 (median: [IQR]: 45.4 min [30.0-74.7]) and longest for Tier 4 facilities (160.2 min [107.3-260.0]). There was a weak spatial autocorrelation across tiers (Tier 1: -0.289, Tier 2: -0.292, Tier 3: -0.271 and Tier 4: -0.258) and few districts were classified as significant spatial outliers. Across tiers, geographic patterns of populated districts surrounded by neighbours with short travel time and sparsely populated districts surrounded by neighbours with long travel time were observed. Similar spatial correlation measures across health system levels suggest that Tanzania's health system reflects equitable urban-rural access to different PALM services. Longer travel times to hospital-based care could be ameliorated by shifting specialized diagnostics to more accessible lower tiers.

Effectiveness of inhaled hypertonic saline application for sputum induction to improve Mycobacterium tuberculosis identification in patients with pulmonary tuberculosis

BACKGROUND

This study assessed the effectiveness and diagnostic significance of hypertonic saline sputum induction for improving Mycobacterium tuberculosis (MTB) detection.

METHODS

A prospective, randomized, open, two-arm, comparative study on MTB identification effectiveness when using inhaled sodium chloride hypertonic solution was performed in patients diagnosed with pulmonary tuberculosis (TB). Patients were randomly assigned into two groups: group 1 (inhalation group) included patients who inhaled a 7% sodium chloride solution upon admission to the hospital, and group 2 (control group) coughed up their sputum as usual. For both groups, specimens were tested by bacterioscopic, bacteriological, and molecular genetic methods. Diagnostic chest radiography was performed for all participants.

RESULTS

In this study, 644 patients (mean age 42.2 years; 151 women, 23.4%) were randomly divided into two groups. Low-quality sputum samples were observed in 7.4% of patients from the inhalation group and 28.8% in the control group (p < 0.001). Acid-fast bacilli (AFB) smear was positive in 65.1% of patients from the inhalation group and 51.3% of controls (p = 0.002). A similar statistically significant situation was observed when culture methods (93.9% inhalation group and 81.9% control group, p < 0.001) and molecular genetic tests (92.2% inhalation group and 79.4% control group, p < 0.001) were used. Thus, active pulmonary TB was not verified microbiologically in 6.1% of patients from the inhalation group and in 18.1% of controls (p < 0.001).

CONCLUSIONS

Hypertonic saline sputum induction improves the quality of collected samples. This method may be appropriate to increase the rate of MTB detection in sputum using microscopic, bacteriological, and molecular genetic methods for diagnosing TB on the day of specimen collection. Hypertonic saline sputum induction is suitable for middle- and low-income countries with limited resources and causes no severe adverse effects in TB patients.

Health Economic Evidence of Point-of-Care Testing: A Systematic Review

OBJECTIVE

Point-of-care testing (POCT) has become an essential diagnostic technology for optimal patient care. Its implementation, however, still falls behind. This paper reviews the available evidence on the health economic impact of introducing POCT to assess if poor POCT uptake may be related to lacking evidence.

STUDY DESIGN

The Scopus and PubMed databases were searched to identify publications describing a health economic evaluation of a point-of-care (POC) test. Data were extracted from the included publications, including general and methodological characteristics as well as the study results summarized in either cost, effects or an incremental cost-effectiveness ratio. Results were sorted into six groups according to the POC test's purpose (diagnosis, screening or monitoring) and care setting (primary care or secondary care). The reporting quality of the publications was determined using the CHEERS checklist.

RESULTS

The initial search resulted in 396 publications, of which 44 met the inclusion criteria. Most of the evaluations were performed in a primary care setting (n = 31; 70.5%) compared with a secondary care setting (n = 13; 29.5%). About two thirds of the evaluations were on POC tests implemented with a diagnostic purpose (n = 28; 63.6%). More than 75% of evaluations concluded that POCT is recommended for implementation, although in some cases only under specific circumstances and conditions. Compliance with the CHEERS checklist items ranged from 20.8% to 100%, with an average reporting quality of 72.0%.

CONCLUSION

There were very few evaluations in this review that advised against the implementation of POCT. However, the uptake of POCT in many countries remains low. Even though the evaluations included in this review did not always include the full long-term benefits of POCT, it is clear that health economic evidence across a few dimensions of value already indicate the benefits of POCT. This suggests that the lack of evidence on POCT is not the primary barrier to its implementation and that the low uptake of these tests in clinical practice is due to (a combination of) other barriers. In this context, aspects around organization of care, support of clinicians and quality management may be crucial in the widespread implementation of POCT.

Determining the value of TB active case-finding: current evidence and methodological considerations

Active case-finding (ACF) is an important component of the End TB Strategy. However, ACF is resource-intensive, and the economics of ACF are not well-understood. Data on the costs of ACF are limited, with little consistency in the units and methods used to estimate and report costs. Mathematical models to forecast the long-term effects of ACF require empirical measurements of the yield, timing and costs of case detection. Pragmatic trials offer an opportunity to assess the cost-effectiveness of ACF interventions within a 'real-world´ context. However, such analyses generally require early introduction of economic evaluations to enable prospective data collection on resource requirements. Closing the global case-detection gap will require substantial additional resources, including continued investment in innovative technologies. Research is essential to the optimal implementation, cost-effectiveness, and affordability of ACF in high-burden settings. To assess the value of ACF, we must prioritize the collection of high-quality data regarding costs and effectiveness, and link those data to analytical models that are adapted to local settings.

Current state of the art in rapid diagnostics for antimicrobial resistance

Antimicrobial resistance (AMR) is a fundamental global concern analogous to climate change threatening both public health and global development progress. Infections caused by antimicrobial-resistant pathogens pose serious threats to healthcare and human capital. If the increasing rate of AMR is left uncontrolled, it is estimated that it will lead to 10 million deaths annually by 2050. This global epidemic of AMR necessitates radical interdisciplinary solutions to better detect antimicrobial susceptibility and manage infections. Rapid diagnostics that can identify antimicrobial-resistant pathogens to assist clinicians and health workers in initiating appropriate treatment are critical for antimicrobial stewardship. In this review, we summarize different technologies applied for the development of rapid diagnostics for AMR and antimicrobial susceptibility testing (AST). We briefly describe the single-cell technologies that were developed to hasten the AST of infectious pathogens. Then, the different types of genotypic and phenotypic techniques and the commercially available rapid diagnostics for AMR are discussed in detail. We conclude by addressing the potential of current rapid diagnostic systems being developed as point-of-care (POC) diagnostic tools and the challenges to adapt them at the POC level. Overall, this review provides an insight into the current status of rapid and POC diagnostic systems for AMR.

Determining virological suppression and resuppression by point-of-care viral load testing in a HIV care setting in sub-Saharan Africa

BACKGROUND

This prospective pilot study explored same-day point-of-care viral load testing in a setting in Ghana that has yet to implement virological monitoring of antiretroviral therapy (ART).

METHODS

Consecutive patients accessing outpatient care while on ART underwent HIV-1 RNA quantification by Xpert. Those with viraemia at the first measurement (T0) received immediate adherence counselling and were reassessed 8 weeks later (T1). Predictors of virological status were determined by logistic regression analysis. Drug resistance-associated mutations (RAMs) were detected by Sanger sequencing.

FINDINGS

At T0, participants had received treatment for a median of 8·9 years; 297/333 (89·2%) were on NNRTI-based ART. The viral load was ≥40 copies/mL in 164/333 (49·2%) patients and ≥1000 copies/mL in 71/333 (21·3%). In the latter group, 50/65 (76·9%) and 55/65 (84·6%) harboured NRTI and NNRTI RAMs, respectively, and 27/65 (41·5%) had ≥1 tenofovir RAM. Among 150/164 (91·5%) viraemic patients that reattended at T1, 32/150 (21·3%) showed resuppression <40 copies/mL, comprising 1/65 (1·5%) subjects with T0 viral load ≥1000 copies/mL and 31/85 (36·5%) subjects with lower levels. A T0 viral load ≥1000 copies/mL and detection of RAMs predicted ongoing T1 viraemia independently of self-reported adherence levels. Among participants with T0 viral load ≥1000 copies/mL, 23/65 (35·4%) showed resuppression <1000 copies/mL; the response was more likely among those with higher adherence levels and no RAMs.

INTERPRETATION

Same-day point-of-care viral load testing was feasible and revealed poor virological control and suboptimal resuppression rates despite adherence counselling. Controlled studies should determine optimal triaging modalities for same-day versus deferred viral load testing.

FUNDING

University of Liverpool, South Tees Infectious Diseases Research Fund.

Management of drug-resistant tuberculosis

Drug-resistant tuberculosis is a major public health concern in many countries. Over the past decade, the number of patients infected with Mycobacterium tuberculosis resistant to the most effective drugs against tuberculosis (ie, rifampicin and isoniazid), which is called multidrug-resistant tuberculosis, has continued to increase. Globally, 4·6% of patients with tuberculosis have multidrug-resistant tuberculosis, but in some areas, like Kazakhstan, Kyrgyzstan, Moldova, and Ukraine, this proportion exceeds 25%. Treatment for patients with multidrug-resistant tuberculosis is prolonged (ie, 9-24 months) and patients with multidrug-resistant tuberculosis have less favourable outcomes than those treated for drug-susceptible tuberculosis. Individualised multidrug-resistant tuberculosis treatment with novel (eg, bedaquiline) and repurposed (eg, linezolid, clofazimine, or meropenem) drugs and guided by genotypic and phenotypic drug susceptibility testing can improve treatment outcomes. Some clinical trials are evaluating 6-month regimens to simplify management and improve outcomes of patients with multidrug-resistant tuberculosis. Here we review optimal diagnostic and treatment strategies for patients with drug-resistant tuberculosis and their contacts.